The third major neo-Kantian thinker to emerge in the 1870s is Alois Riehl (1844–1924). Unlike Cohen and Windelband, Riehl never became the leader of a major neo-Kantian school, though he was a renowned teacher and lecturer. Among his students were Eduard Spranger (1882–1963), Heinrich Scholz (1884–1956), Max Frischeisen-Köhler (1978–1923), Oswald Spengler (1880–1936), Hans Reichenbach (1891–1953) and Richard Hönigswald (1875–1947), all of whom became noteworthy scholars or philosophers in their own right.1 Last but not least, though not among his students, the young Herbert Feigl (1902–1988) and Moritz Schlick (1882–1936) were much influenced by Riehl.2
Riehl was born in Bozen (Bolzano), which is now part of Italy, though it was then part of Austria. Since he grew up in the Tirol mountains, he liked to call himself a “Tiroler Bauer”.3 All his life he loved to hike in the hills, and it was after one such excursion, when he was only 12, that he discovered in a Weingarten a friend’s copy of the Kritik der reinen Vernunft.4 He started reading it, and never really stopped for the rest of his days. After attending Gymnasium in Bozen, Riehl studied philosophy, history and geography at the universities of Vienna, Munich, Innsbruck and Graz. Though he left Austria in 1882, a little bit of Austria went with him. He was the only neo-Kantian to be raised a Roman Catholic; and during his university days in Vienna, he came under the influence of Austria’s “official philosopher”: Johann Friedrich Herbart.5 It was Herbart who planted the seeds of realism in Riehl’s thinking. Through Riehl we can still hear the last faint echoes of the lost tradition.
For most of his career, Riehl was an academic nomad. He held posts in Graz (1873), Freiburg (1882), Kiel (1895) and Halle (1898). Finally in 1904, at the ripe age of sixty, he reached the pinnacle of success with an appointment in Berlin. He taught there until 1921, retiring to a house, designed for him by the up-and-coming Walter Gropius, in Neubabelsberg. Of all the neo-Kantians, Riehl had the greatest international stature. In 1913 he received an honorary doctorate from Princeton University; in 1917 he went to the Baltic states on a lecture tour; and in 1923 he was invited to give a lecture at the University of London, though he had to decline because of his age. Despite his illustrious career, Riehl, like so many neo-Kantians, suffered for his political and religious convictions. An early writing on religion had incurred the disfavour of the Catholic authorities,6 so that Catholic theology students and faculty in Freiburg were prohibited from attending his lectures. Indignant, Riehl’s response was to convert to Protestantism and to leave Freiburg for Kiel, which had a freer atmosphere for him.
Riehl’s major work was his Der philosophische Kriticismus, which appeared in three volumes from 1876 to 1887.7 Its chief aim was to criticize and develop Kant’s philosophy, to re-interpret and revise it so that it was more in accord with the positive sciences.8 Volume I treats the history of the critical philosophy and the interpretation of Kant’s method. Volume II/1 examines the foundations of knowledge, and volume II/2 concerns issues in metaphysics and the philosophy of science. This tome is one of the classics of the neo-Kantian tradition, deserving to stand alongside Cohen’s Kants Theorie der Erfahrung and Lange’s Geschichte des Materialismus. Though its sheer length places great demands on the reader’s time and energy, it also rewards his efforts with its many insights and ideas. Riehl wrote with great clarity and vigour, and took an original and interesting stand on all the central questions facing the critical philosophy. The book was quite successful in its day, and it was a token of its success that it was translated into English, Dutch, Japanese, Russian and Hungarian. Riehl rewrote many parts of the work for a second edition, though it was published in its complete form only posthumously, from 1924 to 1926.9
Riehl was very much a champion of the new epistemological approach to Kant characteristic of the 1870s. He agreed with Cohen and Windelband about the essentially epistemological nature of Kant’s enterprise, and joined them in helping to defeat the psychological interpretation that was so predominant in the 1860s. There was, however, something new and distinctive about Riehl’s approach to Kant, something that sets him apart from Cohen and Windelband. Namely, Riehl stresses the realistic dimension of Kant’s philosophy. He maintains that Kant’s philosophy is a form of realism insofar as it affirms the existence of things-in-themselves, which we know to be the ground of appearances, and insofar as it affirms the existence of a given manifold of sensation. The very thing-in-itself that Cohen and Windelband were so desperate to remove from the body of Kant’s philosophy, Riehl was equally determined to retain; he argued that the thing-in-itself is not inconsistent with but the very foundation of Kant’s philosophy. The heir of Riehl’s interpretation, though it was never acknowledged, was Martin Heidegger.
Realism was the leitmotif of Riehl’s philosophy, its signature theme. Riehl first expounded his realism in his first philosophical writing, his Realistische Grundzüge of 1870. One of the main tasks of Der philosophische Kriticismus is to explain and defend his early stand on behalf of realism. We shall soon see, however, that Riehl’s realism has no simple and straightforward meaning, and that he vacillated between a weaker and stronger form of the doctrine. It should come as no surprise, therefore, that the doctrine has often been misinterpreted, either as a form of materialism or identity philosophy.
Concerning Riehl’s relationship with Cohen and Windelband, his two great contemporaries, very little is known. In the early 1870s he wrote positive reviews of Cohen’s Kants Theorie der Erfahrung and Windelband’s Über die Gewißheit.10 Windelband thought enough of Riehl to recommend him as the successor to his post in Freiburg; but Heinrich Rickert, Windelband’s student, tells us that Riehl, for reasons best known to himself, did not like Windelband and thought little of him.11 What Cohen thought of Riehl is unknown.12
The most controversial question surrounding Riehl concerns his complex and tricky relationship to positivism. After his death, Riehl’s friends and students were divided. Heinrich Rickert, a friend from Freiburg days, insisted that Riehl was no positivist: his realism demanded belief in the existence of a thing-in-itself, which could not be resolved into the positivist’s facts of experience.13 But Heinrich Maier, a student, thought Riehl more a positivist than a neo-Kantian: he taught respect for facts and he surrendered all claims to knowledge to the positive sciences.14 Indeed, Riehl outdid the positivists themselves, because, unlike Comte and Spencer, he saw no role for philosophy as a conspectus or system of the individual sciences. Even today, Riehl is readily classified as a positivist, and he is often cited as one of the main figures in forging an alliance between neo-Kantianism and positivism in the late 1870s and early 1880s.15
There is no simple answer to this question. Since Riehl accepted and rejected important strands of positivism, his philosophy is neither entirely positivist nor anti-positivist. There are indeed important positivist themes in his philosophy. Riehl rejected the metaphysics of classical philosophy, and he indeed insisted that all knowledge of the world lies with the positive sciences. He even declared criticism to be “the foundation of positive philosophy”.16 For many years Riehl was an editor of the Vierteljahrschrift für wissenschaftliche Philosophie, a journal promoting the positivist agenda of “scientific philosophy”. He also acknowledged the influence upon him of Eugen Dühring, the arch German positivist.17
However, these positivist strands have to be balanced against even weightier anti-positivist ones. Riehl protested against positivist attempts to replace philosophy with science as well as positivist attitudes towards the history of philosophy. If he held that the sciences alone give us knowledge of the world, he also insisted that philosophy still plays a crucial role in helping the sciences understand philosophical issues. And, like a good Kantian, Riehl had no time for positivist naivety about facts, which for him were never simply given but the product of conceptual interpretation.18 It is decisive against the positivist interpretation that Riehl himself, in a late essay,19 contrasted the Kantian approach to epistemology with the positivist, and came down firmly on the Kantian side. He conceived his own realism in opposition to positivist phenomenalism, which would reduce an object down to the sum total of its sensations. The existence of an object independent of sensation—the central principle of his own realism—he made into a condition for the possibility of knowledge itself.20
Of all the neo-Kantians of the late 19th century, Riehl was the most challenged by the popular demand for reflection on the mystery of existence. The positivist strands of his thought did not fit well with that demand. Riehl had been very strict and adamant in stressing the purely epistemological role of philosophy, in handing over all knowledge of the world to the positive sciences, and in banishing worldviews from philosophy. He realized all too well, however, that he could not simply turn his back on the question of existence, because this would have indeed doomed his philosophy to obsolescence. Riehl’s response to the crisis was drastic and dramatic: to divide philosophy into a scientific and non-scientific half. Beginning in the late 1880s, Riehl devoted much of his time and energy to this “non-scientific” philosophy. Yet that begged the question how this aspect of philosophy could be intellectually rigorous and respectable. Riehl seemed to have hoisted himself on his own petard. It was more his reputation as a hard positivist, rather than his neglect of the latest developments in the sciences, that explains the rapid demise of his philosophy after his death.21
It is clearly impossible in a single chapter to do justice to the many aspects of Riehl’s philosophy. Our task therefore will be a very limited one: to understand the sources and meaning of Riehl’s realism, his signature doctrine and his chief contribution to the neo-Kantian tradition. The account we give here of Riehl’s philosophical development, which is based only on his published writings, will be crude and sketchy, the result of a lack of documentary materials.22
The origins of Riehl’s thought lie in a little tract he published in 1870, Realistische Grundzüge.23 Though he later dropped some of its themes, this tract still anticipates doctrines of his mature philosophy, especially his realism and interpretation of Kant.24 From it, we can understand much about the motives and reasoning behind them.
In his ‘Vorwort’ Riehl describes his philosophy as “syncretic”, an attempt to combine the best in the philosophies of Leibniz, Herbart and Kant. We do well to take Riehl at his word here and to see his philosophy as a synthesis of these three philosophers; it would be onesided to interpret it only as a Herbartian metaphysics.25 If Riehl corrects Kant through Herbart, he also completes Herbart with Leibniz, who plays the central role in his synthesis. Riehl’s early work might well be described as a neo-Leibnizian metaphysics, though much of that metaphysics would disappear in his mature philosophy.
The young Riehl would have bristled at the label “neo-Leibnizian metaphysics”. That is first and foremost because he never expressly intended to rehabilitate metaphysical dogmatism. He professed to abhor metaphysics, and he understood his project chiefly in critical terms, as a second-order investigation into the fundamental concepts by which we understand and interpret experience, viz., matter, force, cause, change and motion. Any philosopher who built his system without a prior critique of these concepts, Riehl warned, was in danger of having his edifice torn down by the critical philosopher, “this intellectual building inspector” (dieser wissenschaftlichen Baupolizei) (3).
Yet, the more closely we examine Riehl’s project, the more metaphysical it reveals itself to be. He first describes it as a “critique of concepts”, as a “fundamental science” (Fundamental-Wissenschaft), whose basic task is to create a system of concepts (3, 6). But this system is not, as these descriptions suggest and as Riehl would like us to think, simply a second-order account of the logic of concepts. For we soon learn that the ultimate goal of any such investigation is “to reach the real (das Reale) through its sensible appearance and disguise”, and that “the aim of enquiry” is “knowledge of the real” (6). Philosophy seeks to acquire, Riehl tells us in no uncertain terms, “a realistic concept of the world” (einen realistisch ausgebildeten Weltbegriff) (6). So, as much as Riehl professes to abhor metaphysics, his project proves to be nothing but that under a critical disguise. Its basic aim is to provide not a second-order knowledge of concepts but a first-order knowledge of the world, and indeed a knowledge of reality in itself. Here is indeed the starting point of Riehl’s later realism.
We would be selling Riehl short, however, if we exaggerate the dogmatic or metaphysical dimension of his early project. It is not as if he, like Schelling, were “shooting absolute knowledge out of a pistol”.26 Though Riehl is indeed engaging in a metaphysics, it is meant to be a critical metaphysics, one which takes its path through the critical philosophy itself. The realistic elements in his project will emerge from a close examination of the chief presuppositions of Kant’s epistemology. Hence Riehl immediately warns his sceptical reader that “there are more realistic elements in the critical philosophy than one would think” (7).
The starting point of Riehl’s realism was Herbart’s observation that there is a startling gap in the critical philosophy between the general forms of possible experience and the given content of sensation. However much the critical philosophy is idealistic about these general forms, ascribing their origins to the self-conscious subject, it has to admit a kind of realism about the particularities and determinate relations between sensations, which must be just given to us. What these particularities and relations are, when, where and how they appear, is independent of our self-conscious activity, our will and imagination. From the general a priori forms of intuition and the understanding we cannot derive the particular facts of experience, more specifically, how one particular kind of sensation stands in relation to another particular kind. As Kant himself put it, the particular empirical laws of nature are “contingent for the human understanding”, given that they are only one possible form to instantiate its general categories.27 The foothold for Riehl’s realism lay precisely here: that these determinate relationships, these particular truths, are given for the forms of understanding and sensibility. They have their source not inside but outside us. Riehl rejected Fichte’s attempt to deduce the manifold from the ego as well as Schopenhauer’s attempt to explain it as the product of a blind will (6). If these projects are indeed impossible—and few philosophers in the 1870s believed they were feasible—then philosophy had to begin by explaining the hard facts of experience. These, and nothing less, would be the basis of Riehl’s “realistic worldview”.
Despite his critical starting point, Riehl’s metaphysical intentions are still plain and brazen, even if he does not want to describe them as such. For the subject matter of his realistic philosophy is nothing less than things-in-themselves! Riehl was eager to trespass and explore the very terrain prohibited and posted by Kant. Sure enough, the very first chapter of the Grundzüge begins with a theory about the most basic entities of the world, which we can call monads with Leibniz, reals with Herbart or things-in-themselves with Kant. Riehl postulates these entities to explain the objective component of sensation, that is, the component that does not depend upon the subject’s will and imagination, and that is the cause of its sensation (11). Though this being cannot be known directly, though we know it only through its appearances, we can still know it indirectly, by making inferences from appearances (17). This is because, Riehl later explains, sensations correspond to their stimuli in a law-like manner, so that from the constant determinate relations between particular sensations we can infer constant determinate relations between things themselves. Even though the sensations are qualitatively distinct from their stimuli, depending on the sense organs, the particular relations between them depend on objects themselves (27–28). Unabashedly, Riehl is willing to apply the categories beyond appearances to things-in-themselves. Beginning from the assumption that they are the causes of the content of experience, we can begin to develop an entire theory about them.
Quickly, perhaps all too quickly, however, the reader of the Grundzüge soon finds him/herself launched into the wonderland of Herbart’s metaphysics, which provides much of the contours of Riehl’s ontology. Our passport into this world is not any empirical or analytic method but the ways and means of sheer a priori excogitation. We do not make careful and gradual inferences about things-in-themselves from the structure of appearances; rather, we reflect on what is meant by a thing-in-itself, and it turns out that we can know much about them through sheer a priori reflection. The most simple concept we apply to reality in itself, Riehl informs us, is being (Sein). But being in itself means something absolute and simple. It is absolute in the sense that it has an independent reality, depending on nothing else to exist; and it is simple in the sense that it is an indivisible unity, resisting all partition in thought. Since these things are the grounds of appearances, and since there are a multitude of different appearances, we are justified in assuming, Riehl argues, that there is a variety of simple basic entities (11). From this simple analysis weighty consequences follow. We can think of these simple entities as atoms, perfectly in accord with modern physics. But we need to realize, Riehl declares with the ghost of Leibniz speaking through him, that these atoms are non-physical and non-spatial beings (18).28 The physicality and spatiality of things is entirely due to the composition and aggregation of atoms, so that the simple things themselves cannot be spatial or physical at all. It follows from this point, Riehl further contends, that there is no such thing as matter as such. Matter is a composite or aggregate of more simple things, so that to believe that it is a thing itself is simply the hypostasis of an abstraction (20).
Nothing better shows the depth and extent of Riehl’s new realism than his response to Kant’s theory of space and time (21–42). The Transcendental Aesthetic, which Fischer, Meyer, Lange and Schopenhauer regarded as the model of philosophical reasoning, Riehl finds deeply problematic. He cannot accept the central idealist thesis behind the Aesthetic: that space and time are only subjective a priori forms of intuition, such that space and time would disappear if there were no human beings with their characteristic sensibility. He maintains, however, that there are realist elements or tendencies to Kant’s theory which only need to be developed to explode its idealist thesis. Thus Riehl points out that Kant never intended to derive the determinate spatial relations between things from the a priori intuition of space in general, and that he even attempted to derive spatial relations from dynamic ones, from the attraction and repulsion between bodies (23). Furthermore, he notes that Kant expressly denied that space is an innate idea that precedes our perception of things in space, and that he held that we develop our idea of space by our reaction to determinate spatial relations (23). All that Kant’s arguments forbid, Riehl insists, is that our subjective idea of space is qualitatively like real space (23). Kant, however, did not expressly limit his conclusions in this way. His intention was to uphold the strictly subjective status of space and time; hence he explicitly stated that space and time are only a priori intuitions, and that they would completely disappear if there were no human beings (23). There was a reason for this Kantian subjectivism, Riehl explains, which derives from Kant’s intention to save faith. Kant did not want the world of things-in-themselves to be spatial or temporal because he needed a distinct kind of noumenal world to save transcendental freedom (24).
Whatever the implicit realist tendencies of Kant’s Transcendental Aesthetic, Riehl does not think that they are enough to save his theory. The theory of space and time he goes on to sketch in the Grundzüge is the virtual reversal of Kant’s. Rather than holding that spatial and temporal order depend on human perception, Riehl argues just the opposite: that we human beings perceive things temporally and spatially only because we have been conditioned to do so by the spatial and temporal order of things themselves (24, 25–26). There is an objective order of space that arises from the interrelations between things. Space does not precede these things as a vast receptacle in which they are placed; rather, these things are the basis of space itself. In other words, if there were no things, there would be no relations between them; and if there were no such relations, there would also be no subjective space (33–34). Space, as the interrelations between things, arises from the aggregation or composition of simple entities, an order that Riehl, following Herbart, calls “intelligible space”. We do not perceive this intelligible space directly, but we know it though pure thinking, by inferring it from the correspondence between the order of things in our sensible space and their causes (28).
Thus far, Riehl’s theory of space closely follows Herbart and Leibniz, and it seems to have no Kantian element at all. Riehl maintains, however, that there are two orders of space, one objective and another subjective, and that the Kantian theory is broadly correct about subjective space. Riehl agrees with Kant that there is an a priori dimension to our concept of space and time. We must not understand this a priori dimension as an innate idea, however, but simply as a universal psychological disposition to construct the idea of space as a single infinite magnitude. There is no such infinite space in nature, but we proceed as if it exists because we can naturally extend our idea of place beyond any given magnitude (32–33).
Given the importance of Kant’s theory of space and time for his transcendental idealism, and given Riehl’s sharp criticism of that theory, we are left wondering if there is much of Kant left in Riehl’s “syncretic” philosophy. The Kantian dimension of his philosophy seems limited to its methodology, to the critical investigation of knowledge, and nothing more. But Riehl himself carefully corrects this impression in the final chapter of the Grundzüge, which discusses the relationship between appearances and things-in-themselves along Kantian lines. He very much wants to uphold Kant’s distinction between appearances and things-in-themselves, and is very far from wanting to affirm a kind of direct or transcendental realism, according to which how things appear to us is the same as they are in themselves. Although Riehl does not accept Kant’s theory of space and time, he still affirms the central Kantian thesis that our cognitive faculties condition what we know, so that what we know are the appearances of things-in-themselves. His only worry with the distinction between appearances and things-in-themselves is that it is used to defend a two-worlds doctrine like that of Schopenhauer, which would place appearances in the realm of phenomena and things-in-themselves in the realm of noumena (64). Appearances are not a distinct kind of entity apart from things-in-themselves, Riehl explains, because they are simply those things as they appear to us, as they are perceived by us. We are perfectly correct in our normal speech when we say ‘This is red’ rather than ‘I see this as red’ because the object is indeed red; it is just an objective fact about it that it is red in relation to human beings (65). The relation of things-in-themselves to appearances, Riehl explains, has to be understood along the lines of the relation of simple things to their composite products (65). Although what exists are masses of independent substances, what we perceive is joined together by the senses to form a single appearance. This analogy brought Riehl’s theory very close to Leibniz’s, who understood appearances as confused representations of things-in-themselves. That this was hardly orthodox Kant goes without saying, and it reveals again the Leibnizian dimension of Riehl’s early metaphysics.
There are three salient principles or ideas that determine the contours of Riehl’s early philosophy, all of which are more or less explicit in the Grundzüge. The first principle is Riehl’s nominalism, which appears in his statements that everything in nature is individual, and that the universal exists only in and for thinking (13). This principle has significant consequences for Riehl, which he does not hesitate to draw and explain. First of all, it means that there is no such thing as power or force in nature, because that concept is only a general term that we use to designate similar appearances in nature (15). Secondly, it means that there is no sense to teleology in the classical sense, which ascribes causal efficacy to mere ideas or forms (57). Hence Riehl’s model of explanation is essentially mechanical. Thirdly, it implies that there is no such thing as empty absolute space or time, which is only an abstraction from the particular relations between things. The second fundamental principle is Riehl’s naturalism, which comes to the fore in his statement that “Knowing too has its historical origins on earth.” (26) Riehl was fundamentally opposed to dualism, any doctrine that would postulate a noumenal, spiritual or intelligible realm independent of the natural world. All things were, at least in principle, explicable according to natural laws. It was this naturalism that was driving Riehl’s realism: because he saw human thinking and willing as parts of nature, he was committed to giving an independent reality to nature. The third basic principle of Riehl’s early philosophy is its vitalism, which here means the doctrine that everything in nature is essentially alive or psychic. It does not mean the doctrine that life is inexplicable in natural or mechanical laws, which is incompatible with Riehl’s naturalism; still less does it mean that there is some vital force behind all natural or organic phenomena, which violates his nominalism. Rather, Riehl was moved towards the metaphysical doctrine of vitalism by the reflection that simple basic entities must be active and dynamic and cannot be inert and static. Since matter arises only from composition, Riehl argues, the distinction between the physical and psychic is not original or primitive (20). We must understand atoms according to “the analogy of psychic beings” that are endowed with an original striving or nisus. We must postulate a continuum in nature, according to the extent or degree this striving is realized; its highest state of development would be consciousness itself (20–21, 54). This vitalistic aspect of Riehl’s early philosophy shows his great debt to Leibniz. It was, however, that aspect that completely disappears in his later work.29
It was altogether a heady concoction, this syncretic philosophy of the young Riehl. It was a combination of Kant’s transcendental idealism with Leibniz’s monadology, all under the direction and discipline of Herbart’s nominalism and naturalism. Although Riehl never claimed originality for his philosophy, generously acknowledging how these three philosophers provided its essential components, he did claim that he had reconciled them, bringing them together into a single coherent system. But had he achieved even this? Despite all his efforts, there were still tensions. Although Riehl had thrown out teleology, he had to admit that there was something to it, because the fundamental elements of the world were endowed with striving, which makes no sense without the concept of a purpose (58–60). But, even more problematically, Riehl’s ontology of monads, of simple independent atoms, made it difficult to explain the interaction between them. How and why do they interact if each of them is self-sufficient, a universe unto itself? That was Leibniz’s classic problem, which Riehl resolved only by the question-begging assumption that each monad causes the sensations of others (48). The problem of explaining the interaction between monads raised broader issues about whether Riehl’s ontology could support his naturalism, which, like all naturalism worthy of the name, has to assume the reality of change and interaction. Finally, Riehl had really given very little justification for the central assumption of his realism: that, somehow, we could know things-in-themselves. He simply assumed that we could make accurate inferences from the order of our sensations to the order of things-in-themselves. But can we? What warranted such a bold practice, especially in the face of Kantian objections? It should come as no surprise that these tensions and unanswered questions set much of the agenda for Riehl’s later philosophy.
Riehl, like all the neo-Kantians, was worried by the obsolescence of philosophy in the modern scientific age. To ensure its survival, he had to explain how philosophy differs from the natural sciences, and how it too has its own unique vocation. Such was the purpose of a little book Riehl published in 1872, Über Begriff und Form der Philosophie.30 In it Riehl stakes out his own position on the obsolescence crisis, which differs in important ways from that of Fischer, Zeller, Meyer and Windelband. Most of his later views about the purpose and method of philosophy are contained in this little book, though it also has ideas which were later discarded.
Only two years separate Riehl’s Grundzüge from Über Begriff und Form der Philosophie yet a marked conceptual distance lies between them. Riehl is no longer a syncretist who wants to combine the best from the great systems of the past. He is much more critical of Herbart, whose method and metaphysics he now rejects, and he no longer gives Leibniz a central role in his thinking. Kant, however, has become more important for Riehl, who praises his transcendental method for having made “the greatest progress towards the resolution of epistemological problems since Aristotle” (61).31 This is not to say, however, that the young Riehl had become a Kantian. As we shall soon see, he distances himself from Kant in important ways.
Riehl begins Über Begriff und Form der Philosophie by sketching a broad historical picture of the relationship between philosophy and science (1–16). Since antiquity, he writes, there have been two basic philosophical traditions (2). There has been the scientific tradition, which is exemplified by Aristotle, and there has been the aesthetic-religious tradition, which is represented by Plato. The Aristotelian tradition had a discursive paradigm of knowledge, according to which we know things through following strict methodological procedures, whose results we elaborate in concepts, judgements and inferences. The Platonic tradition, however, had an intuitive paradigm of knowledge, according to which we know reality through an act of intellectual insight. Such insight transcends all discursive exposition, and we acquire it through inspiration, by cultivating the right feelings and dispositions. By no means a thing of the past, this ancient tradition has its modern protagonists in Schelling and Schopenhauer.
To determine the right method of philosophy, Riehl says, we must choose between these traditions. Not for a moment does Riehl hesitate to decide for the scientific tradition, and he even describes his tract as a polemic against the aesthetic-religious tradition (iv–v). It is a big mistake, Riehl warns us, to confuse aesthetic and religious feeling with scientific knowledge, and it is an even bigger mistake to think it is superior to science or even to rank it alongside science (12). The proper criterion to decide between these traditions is purely pragmatic: we judge them by their fruits. We all know the rewards of the scientific method, whose successes have been spectacular. But what have we gained by the aesthetic-religious approach? All the systems of philosophy that have followed it have met the same fate: they cannot derive the concreteness and determinacy of the actual world from a vague and obsure intellectual intuition (14–15). The aesthetic-religious tradition leaves us with an insurmountable dualism between its pretended knowledge of reality and the hard facts of the empirical world.
In affirming the scientific tradition, and in repudiating the aesthetic-religious one, Riehl reveals his positivist leanings. The positive sciences had now become for him the model of intellectual excellence. If philosophy claims to be a science rather than just an art, then it should follow the methods and standards of the positive sciences (17). It should follow rigorous procedures of induction and deduction; it should strive for clarity in the definition of concepts; and it should consult the facts of experience.
It would be a mistake, however, to see Riehl’s tract as a positivist manifesto. The very opposite is the case: its central argument is directed against positivism, specifically its attempt to dissolve philosophy into science. Riehl’s intent is to save philosophy from its positivist and materialist detractors, to provide it with its own vocation distinct from the sciences. How, one might ask, is this possible if philosophy is to adopt the methods and standards of the positive sciences? Prima facie this seems a recipe for obsolescence rather than survival.
Riehl’s strategy for dealing with this problem is to distinguish philosophy from natural science through their different subject matters. The difference between them lies not in their form or method but in their content or object. What, then, is the distinctive subject matter of philosophy? The proper object of philosophy, Riehl declares, is consciousness (Bewußtsein), so that philosophy is “the doctrine of consciousness” (Bewußtseinslehre) (27). While the proper subject of science is the natural world, the true subject of philosophy is the consciousness of that world. The natural sciences simply remove consciousness from their purview, while history examines it only in its particular instances with no concern with its general structure (27–28). Although the traditional disciplines of philosophy—epistemology, ethics and aesthetics—concern the true, good and beautiful, we need to remember that these objects exist only for some consciousness (28). Hence Riehl thinks that we should define philosophy as “the scientific investigation of consciousness, its objects and laws” (28).
Such a definition immediately raises the question: How does philosophy differ from psychology? Riehl seems to be working with a very narrow definition of natural science, one which limits its subject matter to the natural world. Why, though, adopt such a narrow definition? If we extend the method of science to the psychic world, then it seems we have Riehl’s idea of philosophy, which is indistinguishable from psychology. By conflating philosophy with psychology, Riehl seems to be hastening the demise of philosophy.
A closer look at Riehl’s texts, however, shows that he can avoid this dire conclusion. Riehl has in mind a very specific kind of psychology, one so unlike the usual or normal kind that he might as well call it philosophy. He explains that philosophy differs from psychology in that it deals with psychic content or the objects of consciousness, whereas psychology concerns the origins or causes of consciousness (31). Alternatively: philosophy studies psychic products while psychology examines psychic processes.
Riehl’s distinction between philosophy and psychology is strategic and significant. It is strategic because it is sufficient to secure philosophy a distinctive domain and to save it from obsolescence at the hands of psychology, which really is more concerned with psychic processes. And it is significant for several reasons: because it precedes Brentano’s psychology,32 which will not appear until two years later; because it anticipates the later interpretative psychology of Dilthey, which will not emerge for at least another two decades;33 and because it marks a sharp break with Herbart’s psychology, which had limited itself to psychic processes instead of contents.34 So the young Riehl, if rashly and confusedly, was pushing philosophy in a new and interesting direction.
But as promising as this direction might seem, Riehl had failed to grasp its problems and implications. For the question immediately arose: What method should philosophy use to grasp the contents of consciousness? Riehl had assumed that the methods of philosophy and natural science are the same. But can we use the methods of natural science to analyse, understand and interpret the contents of consciousness? Dilthey would famously argue that this is impossible, and that it is necessary to make a firm distinction between an interpretative psychology, which deals with content, and an explanatory psychology, which concerns origins and laws. Riehl, however, was not ready for such a major distinction. Unlike Dilthey, he had no appreciation of the hermeneutical tradition with its very different methods of interpretation of psychic content. Riehl’s difficulties are compounded by the fact that he agreed with Dilthey about the limits of natural science in explaining the contents of consciousness. While he insisted that the methods of philosophy and science are the same, he went on to argue that consciousness, insofar as it concerns content, is really inaccessible to natural science. The contents of consciousness are too heterogeneous with the laws of motion for them to be explained by, or reduced down to, natural laws (38).
This points towards a larger tension in Riehl’s position. While he insists on aligning philosophy with the sciences, so that they have one and the same method, he also, as his argument unfolds, distinguishes philosophy from the sciences. “No border is more clearly drawn than that between the investigation of nature and consciousness, if by nature we understand the object of physical investigation and not the totality of phenomena” (39). Riehl stresses that the methods of natural science are “patently insufficient” for epistemology, ethics and aesthetics, and that these disciplines need a completely different kind of enquiry whose presuppositions are different from those of natural science (39). What kind of enquiry should this be? To such a basic question Riehl had no answer.
We should not, however, stress this shortcoming. Riehl’s little tract has much more to offer, and we need to do justice to some of its other themes. One of its more striking and important motifs is its compelling defence of philosophy against its positivist or scientistic detractors.35 Riehl strikes a new chord, insisting that the relationship between philosophy and natural science needs a complete rethinking. The commonplace depreciation of philosophy in comparison with the natural sciences rests upon false premises, he argues. It assumes that philosophical method is a priori and deductive, whereas the proper method of the sciences is a posteriori and inductive. All the excesses of Hegelian speculation and Schellingian Naturphilosophie are attributed to the a priori and deductive method of philosophy. The proper scientific method, these critics contend, rests on slow and patient induction, experiment and observation. This position seemed confirmed by Mill’s Logic, which stressed the importance of induction and generalization in natural science. Riehl, however, is highly critical of such empiricism. A purely inductive science is for him a “contradictio in adjecto” (viii). The more we examine the method of the sciences, he argues, the more we see the role of pure thinking, of deductive reasoning, which is vital in formulating the ends of enquiry, in posing questions, and in formulating laws in mathematical terms. If science were mere induction, the enumeration of facts, we would arrive at no general laws at all (51–52). Induction by itself is only an aid in collecting facts but it is not really involved in the proof or verification of a theory. Riehl agrees with the critics of Hegelian speculation and Schellingian construction that they have relied too heavily on pure thinking and that they have imposed constructions on the facts. But he finds that the problem with the speculative tradition does not lie simply with its use of deductive or a priori methods. Such methods are as vital to natural science as philosophy, he insists. To understand the method of science as well as that of philosophy, he recommends that we get beyond a one-sided empiricism and rationalism.
Riehl’s account of scientific method stresses how it rests on the combination of several procedures. “Human knowledge is no simple product that can be produced in one way and according to one formula. The scientific course of proof needs different methods and aids for its completion. Mere induction does not exhaust its nature.” (49) We cannot acquire knowledge through deduction alone, because everything rests on the truth of its premises (50). We need to resort to experience to determine whether premises are true. But to formulate a scientific law, the scientist does not normally wait for a long induction, an enumeration of all the instances. Rather he begins from one example taken as typical, and then generalizes on the basis of intuition. “Intuition is the productive element of each scientific discovery, and the way to discover new truths” (53). There are, then, three fundamental components to scientific method: 1) the use of a priori intuition in the formulation of laws; 2) the use of deduction in determining the consequences of these laws; and 3) the construction of an experiment according to this deduction (54). This procedure confirms, Riehl maintains, Kant’s dictum that we know only what we a priori create. To this extent he cites a maxim of Schelling: “every experiment is a question to nature, to which she is forced to answer; but each question contains a hidden a priori judgment.” That Riehl should cite Schelling approvingly is a sea change from the 1860s and marks the beginning of a reappraisal of the speculative tradition.
Not the least important contribution of Riehl’s tract is its interpretation of Kant (61–71). Only a year after Cohen’s little book and before Windelband, Riehl attacks the psychological interpretation of the critical philosophy and advances a logical account of Kant’s critical enterprise.36 Although the question of the origins and limits of knowledge seems to be psychological, there are two very different ways of approaching it, Riehl maintains. We can attempt to understand the origins or genesis of knowledge, and we can attempt to analyse its essential constituents or content (64). Kant’s primary task was the second one, and only incidentally or occasionally was he concerned with the first. Kant reached his conclusions about the structure of experience not through introspection but through logical analysis (65). His primary concern was not to understand psychological activities or forms of consciousness but to investigate the reasons for and kinds of judgements we make in science, art and morality (65, 70). The psychological interpretation of Kant is especially misleading, Riehl charges, when it comes to the analysis of the a priori. It understands the a priori as if it were some kind of innate idea, some form inhering within consciousness; but Kant himself expressly denies the doctrine of innate ideas. The a priori concerns not some innate structure of consciousness but the necessary and universal conditions of empirical knowledge.
Anticipating some contemporary interpreters of Kant, Riehl wants to distinguish Kant’s method from his transcendental idealism. While he finds the subjectivism of transcendental idealism objectionable, he thinks that Kant’s method was the most important advance in epistemology since Aristotle (61). The great step forward of Kant’s method consists in its logical investigation of the conditions and limits of experience. This analysis was not intended to be psychological, as it is in Locke and Hume, but to be logical, an account of the content rather than causes of our representations. The problem with Kant’s transcendental idealism, however, is that “it ripped consciousness from its place in the totality of nature” (62). Kant created a transcendental subject who stands above and beyond the sphere of nature, and who is the origin of the necessary forms of experience. “Since man is not natureless, he plainly cannot be torn from the ground of nature.” (62) Kant also assumed, arbitrarily, that the a priori forms of consciousness hold only for the subject, excluding the possibility that they are also true of the world itself. Helmholtz was right, Riehl thinks, in holding that the law of causality is a priori yet still valid beyond the strictly subjective sphere (62).
However salutary in itself, Riehl’s rejection of the psychological interpretation of Kant leaves us with some nagging doubts about his general definition of philosophy. Riehl saw Kant’s critical method as central to and paradigmatic for philosophy itself. But if this method is non-psychological, what sense does it make to define philosophy in terms of psychology, as “an investigation into consciousness, its objects and laws”? The psychological connotations of Riehl’s definition of philosophy did not sit well with his purely logical, indeed anti-psychological, account of the method of transcendental philosophy.
Riehl’s tract closes with a remarkable salute to the history of philosophy. Nothing earlier in the tract prepares the reader for what comes in two closing sections: Riehl makes the history of philosophy central to philosophy itself.37 This is surprising even to the closest reader because Riehl had proscribed genetic enquiries from philosophy, and he had banished psychology from the critical philosophy. But now the psychological definition of philosophy returns, and its method is made genetic. Since the central object of philosophy is consciousness, and since consciousness cannot be separated from its development, Riehl reasons, the history of philosophy is integral to philosophy itself (86, 90). Philosophy, Riehl goes as far to say, should be an historical science, and it should adopt an historical method (90). “A phenomenology of spirit, a history of consciousness, development of the ethical, aesthetic and logical spirit, are its [philosophy’s] tasks.” (91) The history of philosophy is now even made into a touchstone of philosophical truth: what proves to be enduring and common to all the systems of the past can serve as a test for the value of new thinking (86). The hero of Riehl’s new historicist conception of philosophy is Hegel, whose historical sense points philosophy towards the future (91). Kant’s philosophy, however, cannot help philosophy in moving in this new and exciting direction because it is fundamentally non-historical (89, 90–91).
What motivated this historicist frenzy? It is not surprising to find that Riehl returned to sobriety and never attempted to realize the programme he had dreamed up in these final sections. Yet his enthusiasm for history is all too understandable if we see it as a reaction against positivism. With an almost indignant fervour, Riehl was assaulting the positivist dogma that the history of philosophy before natural science is only a history of delusion and superstition. The historicist sections were just another respect, then, in which Riehl’s thinking proves to be profoundly anti-positivist.
In 1876, some four years after his tract on method, Riehl published the first volume of his Der philosophische Kriticismus.38 With this volume Riehl’s conversion to Kant is complete. There is no longer any dream of taking philosophy in a historical direction, and there are no longer any qualms about Kant’s unhistorical thinking. Philosophy now means for Riehl first and foremost critical philosophy, that is, the criticism of metaphysics and the investigation of the logic of the sciences (1). The psychological definition of philosophy, which played such a leading role in the tract on method, has now been pushed into the background.39 Riehl now tells us in no uncertain terms: “The critical philosophy of Kant knows no psychology.” (8)
Just what this conversion meant was spelled out by Riehl in his preface. Critical philosophy, Riehl is emphatic, does not mean exclusively the philosophy of Kant. Although Kant was the greatest representative of the spirit of criticism, “the critical manner of thinking” is not exhausted by, or dependent on, Kant’s system (iii). It was one of Kant’s great achievements to have allied philosophy with the natural sciences of his day; but the progress of the sciences since then makes it impossible to remain on Kant’s standpoint (iv). To think in the spirit of Kant, Riehl would have agreed with Windelband, means to go beyond him. And so Riehl says: “My aim is directed toward the critique and continual development of Kant’s philosophy.” (iv)
What makes it necessary to go beyond Kant, Riehl explains, are some fundamental ambiguities in Kant’s system. While one part of Kant’s system is oriented towards the positive sciences, the other part is directed towards “a practical metaphysics” whose chief goal is the moral justification of religious belief. This ambiguity corresponds to another in the Kantian system: things-in-themselves are either the basis of appearances or noumena, the objects of intellectual intuition (iv). We must resolve the first ambiguity, Riehl thinks, by developing the orientation towards the natural sciences and by dropping the practical metaphysics, which has only a reactionary meaning in our present age. We must resolve the second by preserving the ground of appearances and by proscribing noumena, which are spooky speculative entities. After executing both these manoeuvres, we are left with a philosophy that is critical in spirit but one that corresponds only partly with the historical Kant.
As Riehl’s critical attitude towards Kant’s “practical metaphysics” suggests, there was a moral and political agenda behind his new philosophy. This new critical philosophy was meant to be humanist, a philosophy for man, who is urged to build his heaven on this earth, and who is warned not to squander his riches on an imaginary heaven beyond it. “Criticism is the destruction of the transcendent, the foundation of the positive philosophy … It rouses the spirit out of its metaphysical dreams and toward the waking life of the day and reality.” (iii)
The identification of criticism with “the foundation of positive philosophy” reveals Riehl’s sympathy with positivism. It is not least because of this sentence that Riehl’s philosophy has been identified with positivism.40 We must be careful, however, not to lump Riehl under the positivist label, as if it described the essence or whole of his philosophy. Sympathy with some aspects of positivism does not alone make a positivist. There are too many passages in Riehl’s work where he is critical of the positivists for him to be described as a loyal disciple of the positivist cause. Riehl was critical of Comte’s crude empiricism, which gave no place to the form of cognition.41 He disapproved of Dühring’s naive realism, which could not account for the role of the cognitive subject in forming experience.42 And he rejected Laas’s idealism, which ended out in an extreme subjectivism.43 While Riehl, like any good positivist, recommends that philosophy orient itself around the positive sciences, he also preaches that the sciences sometimes lapse into dogmatism and need to learn from philosophy.44
While Riehl goes to some pains to distinguish his critical philosophy from the historical Kant, it would be a mistake to think that the historical Kant is irrelevant to formulating his own position. Some scholars have gone too far in distancing Riehl’s philosophy from the historical Kant.45 The truth of the matter is that Riehl orients his own critical philosophy around “the spirit” of Kantian doctrine, and he does his best to read that spirit into the Kantian letter. Of course, Riehl regards his own philosophy as a species of realism; but this is a form of realism that he finds in Kant’s own system, and which he thinks is the proper interpretation of Kant. He also describes Kant’s philosophy as “an idealism of appearances on a realistic foundation” (10), which is very much, as we shall soon see, an accurate account of his own philosophy. Riehl, like many neo-Kantians, never broke with the habit of conflating what Kant ought to have said with what he really meant and, in his better moments, did say.
This habit is very much in evidence in Riehl’s account of the two major misinterpretations of Kant’s philosophy. The first volume of his work is devoted to rooting out the two most prevalent “prejudices” of Kant exegesis. The first is the psychological prejudice, according to which the main purpose of Kant’s philosophy is the investigation into our mental faculties and the origins of knowledge. Riehl insists that the critical philosophy has nothing to do with psychology, and that it is only an investigation into the grounds for our knowledge (8, 310). The second prejudice is the idealist prejudice, which would conflate Kant’s idealism with Berkeley’s, and which maintains that idealism is both the method and result of Kant’s philosophy (311). Riehl thinks that describing Kant’s philosophy as idealist is completely misleading because Kant never intended to deny the existence of things independent of our consciousness, which he regarded as the grounds of appearances (9, 311). In thus attempting to root out all psychology and idealism from Kant’s philosophy, Riehl shows how far he was from fully distinguishing what he thought Kant should say from what Kant really did say. The historical Kant never intended to purge all psychology from his philosophy, and he described his own doctrine as a species of idealism, calling it “transcendental”, “critical” or “formal” idealism. The mere fact, however, that Riehl thinks his own interpretation is true of the historical Kant shows how closely he wants to follow him.
So much is Riehl concerned with understanding the actual historical Kant that Volume I of Der philosophische Kriticismus is devoted to an accurate account of the origins, context and content of Kant’s first Kritik. The first part, which has chapters on Locke, Hume and Wolff, concerns Kant’s broader historical context. The second part deals with Kant’s intellectual development and the proper interpretation of the Kritik der reinen Vernunft. It is striking that Riehl finds the origins of the critical philosophy in the empiricist tradition of Locke and Hume, which he regards as the most important influence on Kant.46 This is in stark contrast with Cohen’s account, which stresses the role of the rationalist tradition, of Descartes, Leibniz and ultimately Plato. Although Riehl agrees with Cohen in distinguishing Locke’s and Hume’s psychological method from Kant’s critical one, he still thinks that Locke and Hume set the agenda that Kant was intent on following. While Locke and Hume were wrong about method, they were still right about the basic goals of epistemology: the critical examination of the powers and limits of knowledge.
Riehl’s discussion of Locke and Hume in Volume I of Der philosophische Kriticismus reveals his critical view of empiricism, and with it his stance towards positivism itself. As Riehl sees it, Locke and Hume have the same fundamental shortcoming: they have a much too narrow empiricist criterion of knowledge, which judges claims to knowledge strictly according to whether it corresponds to ideas or impressions given in experience.47 While this is a good test for the content of knowledge, it is inadequate for its form. If we adopt their criterion alone, then we have no justification for the universality and necessity involved in the fundamental principles of the natural sciences and common life. Anticipating a later theme of Ernst Cassirer,48 Riehl notes how Locke’s and Hume’s criticism fails to understand the mathematical dimension of natural science.49 Locke’s nominalism made him equate concepts with mere names or generic concepts; and he failed to see how concepts in the natural sciences have an essentially mathematical meaning. Hume’s critique of causality suffers for the same reason: it does not appreciate that in modern science cause and effect stand for the two sides of an equation. The lesson that emerges from Riehl’s treatment of Locke and Hume in Volume I is a negative one for positivism: that if philosophy is to justify the natural sciences, then it has to get beyond empiricism.
A central task of the systematic part of Riehl’s Der philosophische Kriticismus, Volumes II/1 and II/2, was to explain and justify the realism that he had first sketched in 1870 in his Realistische Grundzüge. If that realism was promising and original, it was also problematic and controversial. Riehl had to defend it against not only sceptical or dogmatic idealism but also common sense or naive realism. Riehl’s realism, in its most basic and weak form, stood for two theses: 1) that we have knowledge of the existence of a thing that exists independent of our consciousness of it; and 2) that our knowledge of the essence or nature of a thing depends (at least partly) on our conscious activity, so that we know it only as an appearance.50 The first thesis was at odds with dogmatic idealism, which claims that only ideas exist, so that there is no independent reality for us to know, as well as sceptical idealism, which holds that we know only ideas and can only make uncertain inferences beyond them. The second thesis was in conflict with common sense or naive realism, according to which we know the essence or nature of things as they exist in themselves. The stumbling block of this realism, Riehl maintained, is its naive assumption that representations simply mirror things as they are, that the world is just as it appears to us; this completely failed to take into account the contribution of the knowing subject in forming the object of knowledge.51 While idealism fully recognized that contribution, it took that point to such an extreme that it made it impossible to know an independent reality. After all, if all knowledge is only our own product or construction, how do we see around it to the things themselves? With his realism Riehl wanted to combine the strength of idealism—recognition of the knowing subject’s role in forming the object of knowledge—with the benefit of common sense realism—knowledge of a reality independent of consciousness. But how could we acknowledge that strength without admitting the drastic conclusion that we know only the appearances of things? That was the question.
The central role of realism in Riehl’s book becomes clear from his introductory account of epistemology. The aims and problems of epistemology, as he explains them in the introduction to Volume II/1, revolve entirely around his realism. Riehl states that he is beginning with “the realist hypothesis” that “something exists independent and different from consciousness”, and that the problem of knowledge acquires its meaning and significance from this hypothesis (II/1, 18). The problem of knowledge, Riehl explains, is to answer the question “Under what presuppositions does knowledge have real significance?” (4) The “real significance” (reale Bedeutung) of knowledge means that it is true not only of our representations about the world but of the world itself, that is, the world as it exists independent from these representations.
Riehl understood his formulation of the problem of knowledge to be a move beyond Kant. The central concern of Kant’s critical philosophy, he held, was the critique of metaphysics. This is why Kant wrote a critique of pure reason: pure reason was the modus vivendi of classical metaphysical rationalism (II/1, 17).52 It was not Kant’s main intention to investigate the possibility of knowledge in general or even empirical knowledge in particular. The aims and methods of empirical science were really not a theme in the first Kritik. The Transcendental Deduction demonstrated at best only that the most general a priori concepts are valid of experience; but it did not explain how we acquire knowledge of particular matter of fact, still less empirical laws. This gap in Kant’s transcendental project Riehl now intends to fill. His epistemology will be less about the possibility of metaphysics than empirical science (17).
In attempting to justify his realism, Riehl believed that he was also defending the metaphysical presuppositions of natural science itself. Natural science presupposes that there is an objective world outside our awareness of it, and that furthermore it can provide us with knowledge of this world.53 But how can we begin to justify such an assumption? Riehl immediately notes a major problem for such a project. We cannot prove or disprove the existence of anything; and we determine whether something exists only by experience. Whether that experience is veridical also cannot be demonstrated, because the same empirical content can be in dreams and hallucinations. So Hume was right, Riehl admits, that we can only have faith in the existence of the external world (II/1, 3). He even concedes that his enquiry is caught in a circle. It must justify yet assume the existence of reality in itself (3). Riehl reassures us, though, that the circle is not vicious: the presuppositions of the enquiry will be justified as it proceeds.
Though Riehl recognizes that he cannot prove realism, he still thinks that he can provide an indirect proof for it by considering the problems of idealism. Although idealism is not self-contradictory, it cannot be proven, and even worse it cannot be fully carried out to explain appearances, that is, the apparent independent reality of the external world (II/1, 19–21). Neither Berkeley nor Fichte were successful in pushing through their idealism. To explain the tree in the quad, Berkeley had to postulate the mind of God; and to account for the finitude of the ego, Fichte had to posit an obstacle to its infinite striving. Even Mill’s phenomenalism, which did not deny the existence of things but analysed them into permanent possibilities of sensation, had a similar problem. For Mill had to assume that these permanent possibilities, which are constant and hold for all observers, are based on the permanent and independent reality of some external object. Although the existence of the external world cannot be demonstrated, Riehl does think that it provides us with the simplest and most plausible hypothesis about the recurrence of the same sensations to different observers (21). It is more plausible to assume that these sensations arise from some reality independent of the observers’ perceptions than that they arise from some mysterious pre-established harmony between them.
Assuming that this is the sole justification of realism, it would seem that the philosopher’s task is already complete. There is little point in doing more epistemology, at least on Riehl’s understanding of that discipline. If providing that justification is the chief task of epistemology, as Riehl says, and if we now already have all the justification we are going to get, as Riehl also says, why go any further? Riehl, it seems, need not have written anymore than his introduction. Of course, Riehl had not begun to answer his real problem, which went much deeper. The real problem was not simply to show that there are external objects; it was to determine how, to what extent, and indeed whether, we know them. This deeper problem arose chiefly because Riehl, despite all his criticisms of idealism, was something of an idealist himself. He stresses that the world we know is not only the product of things outside us but also the result of the activities by which we know them (II/1, 4–5). Like a good Kantian, he holds that there are certain a priori laws of consciousness, and that these laws are the precondition of our thinking and perceiving things (11). Hence, to take account of these Kantian assumptions, Riehl reformulates his conception of epistemology. Its task is to determine whether and how a priori concepts are true not only of appearances but also of reality itself (11–12).
The crucial question for Riehl, then, was not whether we should be a realist but what kind of realist we should be. It seemed to him clear that the world exists; but the problem was how, and the extent to which we could know that existing world.54 To solve that problem it was necessary, somehow, to separate the contribution of the knowing subject to experience from its given content—a seemingly impossible task, given that these were completely intertwined. Another part of the problem was that Riehl himself was uncertain about how far to push his realism. The two theses above represent its basic and minimal form; but sometimes Riehl was tempted to push his realism further, so that we have some knowledge of the essence or nature of things themselves. In the Grundzüge he had maintained that though the qualities of things depend upon us, we can still have knowledge of their relations and mathematical form. This stronger form of realism reappears in the Volume II/1 of Der philosophische Kriticismus, though, as we shall eventually see, it disappears again in Volume II/2. The reason for this vascillation we shall examine later.
To clarify Riehl’s realism, we will have to examine closely the details of his epistemology, especially his theory of sensation and space and time. Before we turn to these tasks, however, we can get a better preliminary picture of Riehl’s realism by distinguishing it from two common forms of realism that were close to his own. One was Kant’s empirical realism, the other Locke’s scientific realism. The similarities between them are striking. Both shared a common goal with Riehl: attempting to combine the existence of things outside us with the recognition that the world is, if only partly, the creation of consciousness itself. Yet each form of realism was unique.
According to Kant, transcendental idealism is not only compatible with, but presupposes empirical realism, according to which reality consists in the intersubjective order of consciousness. Although empirical realism teaches that we know only appearances, it still thinks that these appearances amount to reality because they conform to the universal and necessary forms of experience which hold for all observers alike. An appearance should not, therefore, be conflated with an illusion, which violates these rules.
However plausible and appealing, empirical realism was simply not enough for Riehl. He complained that it still leaves us caught inside the circle of appearances, so that we cannot make any claim to knowledge of reality itself. “The mere agreement of representations among themselves, a play of the mind,” he wrote, “can satisfy only a subjective interest.”55 This empirical realism, he insisted, required a deeper and stronger realism to support it.
It would seem that Riehl’s realism is closer to something like Locke’s scientific realism than Kant’s empirical realism. The scientific realist maintains that we have knowledge of a world independent of consciousness; and he avoids the naivity of common sense realism because he does not simply equate our perceptions of the world with the world itself. The scientific realist makes a distinction between secondary qualities, which depend entirely on the perceiver, and primary qualities, which exist in the world itself. These primary qualities are those which we can measure, and which we can formulate in general quantitative laws.
Despite the apparent affinity of their positions, Riehl is a very harsh critic of scientific realism. There is no tenable distinction, he argues, between secondary and primary qualities, because the content of each depends as much on the subject having them as the stimulus that excites them.56 As far as the qualitative aspect of sensations goes, Berkeley was entirely correct in criticizing Locke’s distinction.57 The scientific realist’s attempt to explain sensation was no better than his distinction between primary and secondary qualities. He attempts to explain sensation on the basis of physiological laws, holding that there are strict correlations between sense qualities and the motions of particles or waves striking our sense organs. Riehl objects that these kinds of explanations put the cart before the horse, reversing the true course of ontological priority.58 What we know for certain is the content of sensation, and what we construct on their basis are motions, particles and laws. Rather than explaining sensations on the basis of particles and motions, we need to explain particles and motions on the basis of sensations. The belief in motion, Riehl further contends, is not primitive but constructed, arising from perceiving an object in different places at different times and then postulating a continuum between these perceptions. “To want to observe a movement in itself,” as Riehl ironically puts it, “is to demand to be able to observe without the senses themselves.”59 The last refuge for the scientific realist is his belief in the reality of laws themselves, which seem to hold sway over all the phenomena, whatever these might be. But, for Riehl, this belief is sheer hypostasis. There are no scientific laws as such existing in some realm governing the phenomenal world; we discover in nature only the laws that we make (II/2, 44).
Given Riehl’s rejection of dogmatic and sceptical idealism, of empirical and scientific realism, we are left wondering what kind of realism his could possibly be. Somehow, it would have to walk the middle path between the extremes of idealism and realism. But what is that middle path? And can we really go down it without falling into the precipices on either side? For Riehl, explaining true realism was no easy task. It could come only at the end of enquiry, after investigating the fundamental factors involved in all knowledge, sensation, space and time, and the basic principles of the understanding. Our task now is to see how Riehl’s realism grew out of his analysis of these factors.
Fundamental to Riehl’s realism was his analysis of sensation, which takes place in many places in Der philosophische Kriticismus, primarily in Chapters 1 and 3 of Volume II/1 and Chapter 2 of Volume II/2. Our most basic contact with external reality, Riehl holds, happens in sensation. It is primarily through sensation that we know of the reality of things independent of our consciousness. Hence Riehl writes:
Only following the guiding thread of sensation do we achieve knowledge of the external world; and what we should validate as real must connect with sensation. To verify hypotheses that we form about events in the external world means to demonstrate their connection with sensation and direct perception. (II/2, 34)
How is it that sensation gives us knowledge of an external reality? Riehl thinks that the sense of touch is the most basic in giving us an awareness of an external world (II/1, 203). When we attempt to touch an object, when we try to push or pull it, we feel resistance; the source of this resistance is something external to ourselves. The basic fact that sensations come and go independent of our will and imagination, Riehl also argues, makes it evident that they have a source independent of our own conscious activity (II/1, 188). Descartes imagined that these sensations could be created by some deep subconscious activity within us. But Riehl finds this hypothesis implausible: it cannot explain why this world clashes with our will, and why we have to adjust to it (II/2, 151). If this activity is so powerful as to create the whole world, why does it not make one we like? Riehl also argues that the sheer heterogeneity of sense contents, the very different qualities of the different senses, is evidence for an external world (II/1, 194–195). We would not unite such different contents if there were not one object in which they inhere.
Sensation, for Riehl, gives not only the most certain knowledge of external reality, but also the most certain knowledge in general (II/1, 46). All knowledge has to be based ultimately upon sensation. If we insist with Kant that all knowledge has to be grounded in experience, he argues, then we have to go the further step and hold that it is based on sensations, which are the ultimate elements of experience (26, 47). “The norm of positive knowing, of material truth”, Riehl tells us, “is the guiding thread of sensation.” (47) Since the most certain knowledge is that based on direct concrete sensation, knowledge becomes less certain the more abstract it becomes, the more removed from sensation (46).
What makes knowledge through the senses so certain? One reason, Riehl explains, is that it is immediate, that is, it is not based on inference (II/1, 196). There is no causal inference that takes place when we sense things, as if we tacitly or subconsciously infer that the sensation is the effect of an object which serves as its cause. If that were so, we could make an error by inferring the wrong cause of a sensation. But we make no such inferences. What we sense are real objects, and not simply the ideas, representations or images of them, from which we then infer their causes. Riehl is therefore critical of Helmholtz’s theory of subconscious reasoning,60 according to which the perception of external objects consists in subconscious inferences that are based on visual, tactual and motor cues; he thinks that Helmholtz simply reads his own reconstructions into experience (II/2, 47–49; I, 126). We do not see images on our retina, or feelings at the end of our fingertips, and then construct an object out of them. Where we perceive the object is outside us in space and not inside us in our head through images and feelings (II/2, 56). These images and feelings too are fictions of the physiologist, the product of his analysis of sensation that he hypostasizes and reads into the phenomena (II/2, 56).
So far Riehl’s analysis of sensation seems to be very empiricist. It emphasizes the importance of sensation as the basis of knowledge, and it stresses the passivity of the senses in perceiving things. Yet this is only one half of his theory, which, like Kant’s, is intended to be a fusion of the empiricist and rationalist traditions. True to his Kantian roots, Riehl insists that sensation is not a purely passive response to stimuli, but that the subject plays an important role in shaping even the quality of sensation, which is never simply given (II/1, 50, 59). It is in virtue of this active element, he maintains, that sensation is cognitive, making a claim to knowledge of reality itself. All sensation involves a tacit reference to an object, a localizing of its source to something outside us that is not a sensation (II/1, 34, 42). To that extent it also involves an implicit judgement that something exists, that there is a thing outside us (I, 148; II/1, 32, 42–43). Because we cannot prove such a judgement, sensation involves an element of faith (Glaube), as Hume said, the belief that there is something out there to which we are responding, and that we are not simply imagining things (46).
It seems remarkable that Riehl maintains both that sensation is the most certain form of knowledge and that it is a form of faith. But Riehl’s position is perfectly consistent. He is following Hume, who held that all belief in the external world is certain even though it is indemonstrable. In Volume I he had often discussed Hume’s doctrine, although then he stopped short of approving it (I, 156). Now, in Volume II, he seems to endorse it.
Riehl’s analysis of sensation is partly a reaction against the idealist interpretation, which would deprive sensation of any reference to the existence of something outside it. It is interesting to see how Riehl takes issue with Johannes Müller’s theory of specific nervous energies, which had been cited by Liebmann, Lange and Helmholtz as evidence for this interpretation. According to Müller’s theory, the quality of a sensation depends not on the stimulus but the nerves that perceive it. Riehl counters that the nerves have no specific energies at all, that they are not conditioning factors that determine the quality of a sensation (II/1, 51–53). Basing his argument partly on Wundt’s psychology, Riehl maintains that the nerves are really nothing more than conductors of stimuli that they cannot produce or alter (52). It is a new finding of anatomy, he points out, that all nerves are basically alike and that the differences in their cells are not great enough to account for a change in their function (II/1, 53). Riehl also appeals to the theory of evolution to bolster his case against Müller’s theory (II/1, 56–57, 58).61 Our specific senses are adaptations, evolving in response to different stimuli in the environment. By giving us direct awaress of reality, they help the species to survive by informing it about the threats and opportunities of its world. Müller’s sensations, which inform a creature only about itself, make no sense from an evolutionary standpoint.
Attempting to strike a balance between idealism and empiricism, Riehl maintains that there is both an objective and subjective component involved in sensation. A sensation has an objective component insofar as it refers to some object, to something distinct from sensation; but it also has a subjective component in feeling, which accompanies each sensation (II/1, 37). To sense something is also to feel it, and that feeling means that it never consists of a completely indifferent state of consciousness. Riehl thinks that it is a mistake to make a distinction between subjective and objective sensations along the lines of Locke’s distinction between primary and secondary qualities (II/1, 62–63). Each sensation has a subjective and objective component, and it is as false to regard size and shape as completely objective as it is to hold colour and sound as completely subjective.
The fact that sensations are both subjective and objective means for Riehl that appearances are the product of both the subject who is aware of them and the object that stimulates them (II/2, 30). The content of the sensations is both a psychic as well as a physical fact, and we have to recognize that the facts of experience are “psychophysical”. The result of the interaction between subject and object in perception is appearance, and not merely representation (II/2, 152). It is appearance in the proper sense of the word, that is, the appearance of something. All our knowledge of things is therefore relative, depending on our sense organs as well as the objects that stimulate them. What is not relative to our physiology, however, is the sheer existence of things, which remains the same no matter how many different ways that we perceive it (II/2, 153, 130).
What ultimately emerges from Riehl’s analysis of sensation, then, is a very qualified realism, one so qualified that we can even regard it—horribile dictu!—as a species of idealism. According to this version of realism, all that we know of reality in itself is only its existence, not its nature or essence. What we know of reality depends so much on our cognitive activity that we can say that it does not represent or reflect the nature or essence of reality itself. Still, even though we know only the appearances of things, these appearances are not simply representations or ideas floating in our mind; rather, they are how real things exist relative to us. Appearances are properties of real existing things-in-themselves, it’s just that they are relative properties, how those things exist for human beings with the cognitive faculties that they have. This theory could be described as idealism, because it holds that all the appearances of things exist only relative to our consciousness; but it is also a qualified form of idealism because it insists that the real existence of things is independent of our consciousness. In the Prolegomena Kant himself had described his idealism in just such terms. He called it “formal idealism” because it made only the formal dimension of things depend on consciousness; and he distinguished it from Berkeley’s idealism because it affirmed the existence of things-in-themselves, which Berkeley’s idealism denied.62 Simply because it allowed for the existence of things-in-themselves, Riehl took issue with the tag “formal idealism”, claiming that Kant’s doctrine should not be called an idealism at all (II/2, 137). But this was more a matter of nomenclature than substance.
We are still very far, however, from a complete analysis of Riehl’s realism. If the realism we get at the end of his analysis of sensation is very thin and flimsy, limited to affirming only the existence of things-in-themselves, the realism we obtain from his theory of space and time is thicker and firmer. For now we learn that spatial and temporal relations are objective, properties of things-in-themselves. The apparently conflicting conclusions can be easily resolved when we consider that sensations account for the qualitative dimension of experience, whereas space and time constitute its quantitative dimension. If this quantitative dimension is true of things-in-themselves, then Riehl’s realism comes close to a scientific realism after all.
This stronger and more robust realism is the chief result of Riehl’s theory of space and time, which is expounded in the longest chapter of Der philosophische Kriticismus, Chapter 2 of Volume II/1.63 The special task of this chapter is to determine which properties of space and time, if any, are objective, and which, if any, are subjective (II/1, 80). It turns out that relations of sucession, simultaneity and co-existence are indeed objective, and that we can have precise scientific measurements of them.
Much of Riehl’s chapter on space and time is devoted to a searching examination of Kant’s theory of space and time in the Transcendental Aesthetic, which is a great challenge to Riehl’s realism. Its central thesis is that space and time have a merely subjective status, that they are the product of the a priori forms of human sensibility, so that if there were no such forms, space and time would cease to exist. Although Riehl was determined to resist this conclusion, he still found much to accept and applaud in Kant’s analysis of space and time. He admits that we need the ideas of absolute space and time to measure motion (II/1, 94); and he stresses that the purely formal features of space and time are a priori, having a subjective source in the mind itself (102, 115, 133). These purely formal features are the homogeneity, continuity and infinitude of the spatial and temporal manifolds. It is just a fact that these purely formal features cannot be derived from experience, and that we can make all kinds of mathematical theorems about them whose truth is strictly a priori. We construct these features of space and time a priori in thought, by reiterating numerically the pure concepts of unity and identity (116, 132).
While Riehl thinks that Kant is right that these formal aspects of space and time are a priori, he also maintains that he is wrong to conclude that space and time have a strictly subjective status, as if they were true of appearances alone. Kant went astray, Riehl argues, in conflating purely formal or mathematical space and time with true or real space and time (115). Homogeneity, continuity and infinitude are true of our idea of mathematical space and time, which we construct in our imagination and according to the concepts of the understanding. Real space and time, however, are based upon particular relations of co-existence and succession, which cannot be determined by the pure forms of space and time, and which we have to learn entirely from experience (116, 128, 129). Kant himself had admitted, Riehl notes, that these purely formal features on their own, which are general and indeterminate, cannot explain or derive the empirical ones, which are particular and determinate (90). This concession gave Riehl the crucial foothold necessary for his own realism.
Among the purely empirical features of space, according to Riehl, is its three-dimensionality. Kant was wrong to think that the three-dimensionality of space is a universal and necessary property of it. The three-dimensionality of space, Riehl insists, is a fact about its content, not its form. Alluding to the new non-Euclidean geometries, Riehl insists that there are no a priori limits to the number of dimensions of space. Though three-dimensionality is true of our experience, it is not the only thinkable or conceivable form of space (166–167). The proposition that space has three dimensions is what Riehl calls an “axiom of experience” because, though it is certain and a basic fact about our world, it is still based on experience (173). Though Riehl is happy to take into account non-Euclidean geometries, it is still noteworthy that he is rather conservative in his view about their application. He thinks that Euclidean space is at the basis of every empirical concept of space (179–180), and he foresees no value in the use of non-Euclidean spaces in physical theory (180).
Regarding the origins of our representations of space and time, Riehl maintains that we acquire them partly from experience, by learning how to co-ordinate our tactual and visual sensations, and partly from applying and exercising our original innate powers. He suggests, however, that the whole dispute between empiricists and nativists is a mistake, because these concepts are acquired both from experience and native activities and dispositions. Although there are no innate ideas of space and time, we could not learn them from experience if we did not already have dispositions to perceive things in certain ways (112–115).
It is striking that Riehl throws out Trendelenburg’s “third possibility” in developing his own realistic theory of space and time (107, 108). If all the particular relations between space and time were determinable a priori, Riehl argues, then we would indeed have to admit that they are only subjective, having no correlate in things themselves. It is not possible for space and time to be completely a priori and subjective in origin and for them to still correspond with things-in-themselves. The problem with Trendelenburg’s third option seems to be—though Riehl does not fully explain—that there would not be a sufficient reason to assume objectivity if the representations of space and time were entirely a priori. Why assume that they are still objective if all relations originate in the mind?
Fortunately, Riehl thinks, we do not have to go down Trendelenburg’s twisted path, simply because spatial and temporal relations themselves do not have an entirely a priori origin. The particular relations of co-existence and succession cannot be derived from the a priori formal and general features of space and time. These particular relations have to be given in experience, and the simplest explanation for their existence and order is that things themselves exist and are ordered in these ways. They appear to be in just these relations independent of our will and imagination just because they exist in these relations, whether or not we perceive them. It was a mistake on Kant’s part, Riehl argues, to claim that what orders sensations in certain relations—the form of experience—cannot be given in sensation itself, because these relations of succession and co-existence are given to us, independent of our will and imagination, just as much as the sensations themselves (II/1, 104). Riehl also gives “realistic significance” to measurement in determining exactly the size of objects themselves and the real distance between them (165). We have good reason to assume that their measured size and distance are properties of the objects themselves, because the reason we must apply the measuring rod or stick exactly so many times lies with the objects themselves and not simply the activity of our measuring them (165).
It now seems, at the end of Riehl’s theory of space and time, that we really have a robust realism worthy of the name. It is not only the existence of things that we know to exist independent of our consciousness of the world. We also know the spatial and temporal relations of these things, and we are even able to measure them precisely. Whatever Riehl’s qualms about the distinction between primary and secondary qualities, we are now fully in a position, it seems, to say with scientific realism that we know the world in itself through its quantitative dimension.
And yet what Riehl gives he also takes away. We shall soon see that Riehl retreated from this bolder realism, and that he did so for all too Kantian reasons. But this will require a little explanation.
Riehl’s Der philosophische Kriticismus was a work in progress. Its three volumes appear years apart from one another—Volume I in 1876, Volume II/1 in 1879 and Volume II/2 in 1887—and during these intervals Riehl’s thinking evolved, and so much so that what he writes in an earlier volume he sometimes contradicts in a later one.64 With the end of Volume II/1 we have the robust realism of his theory of space and time; by the end of Volume II/2, however, we lose that very realism. The reason for the loss concerns Riehl’s theory on the classical mind–body issue. In developing his theory Riehl finds it necessary to distance himself from materialism; but in keeping materialism at bay he also undermines his robust realism.
Riehl develops his mind–body theory, which he expounds mainly in Chapter 2 of Section 2 of Volume II/2,65 to resolve an apparent antinomy in the life sciences. Developmental biology and physiology have completely antithetical assumptions and approaches, yet both seem to be vindicated by experience (II/2, 178–9, 181, 203). Biology assumes that function follows use, and it assigns a great role to consciousness in the survival of an organism; its theory of natural selection works only if we assume that an organism’s consciousness responds effectively to dangers and opportunities in its environment. Physiology, however, sees everything in an organism as the result of physical and chemical processes, where consciousness is the result of nervous processes, which are the result of physical and chemical interactions. While biology assumes the efficacy of consciousness as an agent in nature, physiology regards consciousness as something completely epiphenomenal, the result of physical and chemical interactions. Because both approaches seem necessary and true of experience, Riehl calls this conflict between the disciplines “the physiological antinomy”.
The only reason that the life sciences are caught in this predicament, Riehl claims, is that they have relapsed into a kind of scientific dogmatism, as if the naturalistic view of the world were true of reality in itself (II/2, 182). They assume that the world as analysed by science exists in itself, independent of our consciousness, and they do so because they reify the concept of matter, as if it designated an entity independent of our experience. The natural scientists have therefore failed to heed the chief lesson of Kant’s ‘Paralogismus’ chapter in the Kritik der reinen Vernunft: that both the mental and the physical are aspects of a single experience, and that the idea of matter as an entity existing on its own independent of consciousness is only an hypostasis. The antinomy appears, Riehl argues, only under a certain presupposition: the absolute reality of mechanical events in nature; it disappears as soon as we assume the opposite: that these events are only appearances of the real, whose properties are known to us only by their effects on consciousness (II/2, 181).
Riehl provides several formulations for his solution to the physiological antinomy, though only the most prominent formulation concerns us here. According to that formulation, biology and physiology are two different approaches to, or perspectives upon, one and the same reality (II/2, 191, 196, 199). They do not explain distinct kinds of entity but are simply distinct explanations for one single entity. The activity of consciousness and the will, and the chemical and the mechanical interactions underlying them, are really one and the same activity, though seen from two standpoints (199, 200). When we assume the efficacy of consciousness and the will, we are speaking from a first-person and qualitative standpoint, where we attempt to explain the agent from within; and when we explain consciousness and the will by chemical and physical processes we are taking a third-person and quantitative standpoint (193, 201, 211). To avoid the antinomy, Riehl argues, we must replace a metaphysical dualism with a methodological one (191). Riehl called his own doctrine “critical monism” because it saw a single entity explained by different methods, in opposition to dogmatic dualism which assumed different entities as objects of these different methods.
Whatever its intrinsic merits, Riehl’s critical monism raises the most profound questions about his own realism. For it is a consequence of his critical monism, as he understands it, that the mechanisms of the spatial and temporal world belong only to the appearances of things, not to things-in-themselves. Riehl is perfectly explicit in spelling out this consequence, when he insists that the mechanical explanations of physiology are valid only for appearances and not nature in itself (II/2, 194, 200, 216). After stressing this point, Riehl retreats to his thinner and more anemic conception of realism, according to which we know only the existence but not the essence of things-in-themselves: “And so the proposition still holds: knowledge of our self and things outside us is, although real, still relative regarding the reality of its objects. It is the knowledge of the relations of things to our consciousness, of consciousness to things.” (II/2, 190)66 This point is meant to apply not only to our qualitative knowledge of things in sensation, but also to the quantitative knowledge of things through the measurement of their spatial and temporal relations.
The reason for Riehl’s retreat to the weaker form of realism is not difficult to surmise. It is his fear of materialism. If we assume that knowledge of spatial and temporal relations gives us knowledge of things-in-themselves, as the stronger form of realism wants, then we grant one of the most important premises of materialism: namely, that the spatial and temporal world is valid of things-in-themselves. Riehl defines materialism as “the doctrine of the congruence of external appearance with the external cause of appearance” (II/2, 188), which is exactly what one must accept if one assumes that spatial and temporal relations are true of things-in-themselves. As a good Kantian, Riehl is not willing to allow the materialist the slightest quarter; he insists that his belief in the reality of matter as an independent entity is the result of hypostasis, just as Kant had taught in the first Kritik.
The final result of Riehl’s theory of critical monism, then, is the evisceration of his realism. Rather than the robust doctrine that we know not only the existence but also the spatial and temporal relations of things, his realism again becomes the anemic thesis that we know only the existence of things. That more feeble doctrine, as we have seen, could just as well be described as a form of idealism. But, in the end, Riehl had no choice but to retreat to his weaker realism. He faced a terrible dilemma: hold the critical monism and weaken the realism; or strengthen the realism and support materialism. Riehl chose the former option, though that left him with a very weak form of his signature doctrine. So when all is said and scrutinized, Riehl’s realism proves itself to be only another name for Kant’s formal idealism. Again, this was more a matter of emphasis than substance.
Throughout the history of neo-Kantianism, the greatest stumbling block to the interpretation of Kant’s transcendental idealism had been its concept of the thing-in-itself. Ever since Jacobi’s famous statement that he needed this concept to enter Kant’s system but had to drop it to stay inside it, it has proved to be a great challenge for all neo-Kantians. We have seen how many neo-Kantians—Fischer, Liebmann, Lange, Cohen and Windelband—did their best to dismiss this concept or to re-interpret it in strictly regulative terms. Yet what was for them the greatest weakness of Kant’s philosophy was for Riehl its greatest strength. His realist interpretation of the critical philosophy depends first and foremost on giving full and robust reality to things-in-themselves. Riehl rejected interpretations of the thing-in-itself that construed it in a strictly regulative sense or that made it an ideal of enquiry.
Yet Riehl’s willingness to defend the existence of things-in-themselves placed a great burden upon him. How could he defend their existence in the face of the apparently telling objections against them? Riehl took up these interpretative challenges in the last and longest chapter of the first volume of his Der philosophische Kriticismus,67 to which we must now turn.
Although Riehl is never so explicit, it is fair to say that the starting point for his realist interpretation lies in Kant’s statements that his philosophy is critical or formal idealism. In the Prolegomena Kant had described his philosophy as critical and formal idealism to distinguish it from Berkeley’s idealism, with which it had been conflated.68 A critical idealism is one that sets limits to knowledge, and that forswears all claims about reality in itself. A formal idealism is one that ascribes ideality to the forms of experience, but which maintains that the matter of experience is given to us. In both respects Kant meant to contrast his idealism with Berkeley’s, which is metaphysical, because it claims to know the essence of things, and which is material, because it dissolves the content of experience entirely into ideas. For Riehl, Kant’s statements about his idealism show not only that it is compatible with the reality of things-in-themselves but that it even presupposes them (9–10, 311). It was only by assuming the reality of things-in-themselves that Kant could distinguish his idealism from Berkeley’s (423–424). This was a point on which Kant himself had insisted, which we therefore have to take into account in any proper interpretation.
It might seem, on one plausible interpretation of Kant’s critical idealism, that we should give a strictly hypothetical status to things-in-themselves. After all, if we limit knowledge to experience, we cannot know whether these entities exist or not. As we have seen, this was the interpretation of Kant’s critical idealism set forth by Meyer.69 Riehl, however, rejects this interpretation from the outset, mainly on textual grounds. It was beyond all doubt for Kant, he writes, that things-in-themselves exist and that they are the ground for appearances (9). It never occurred to him that there could be appearances floating on their own, without something that appears (10, 311). Here Riehl cites Kant’s statements to the effect that the very concept of an appearance requires something that appears. In conceiving his idealism as a formal idealism Kant naturally presupposed and expressly assumed that there is some thing-in-itself that is the cause of its matter. Formal idealism means that it is only the forms of experience—the a priori forms of sensibility and the a priori concepts of the understanding—that arise from the knowing subject, so that the content of experience is given. But the very givenness of that content means for Kant, that it has a source that lies beyond the subject and in some object existing independent of it (433). Thus Kant’s philosophy was an idealism in form and a realism in content (10, 312). Or, as Riehl also put it: “Kant’s doctrine is an idealism of appearances on a realistic basis.” (10)
Riehl is highly critical of any strictly dualistic account of the distinction between appearances and things-in-themselves. Appearances and things-in-themselves are simply two aspects of one reality (10, 313). Appearances are things-in-themselves as they happen to appear to us, whereas things-in-themselves are things considered apart from how they affect and appear to human sensibility and understanding. There are two sides or aspects to the concept of appearance, Riehl maintains (425). One side is turned towards the subject, which provides the form of representation; the other side is turned towards the object, which provides the particular material for the form of representation. With these two aspects, Kant walks a middle path between a realistic dogmatism, which just assumes that objects are in themselves just as they appear to us, and an extreme idealism, which reduces appearances down to representations alone.
Riehl felt it necessary to defend his own realist interpretation of the appearance/thing-in-itself distinction against Schopenhauer’s popular idealist interpretation, which converted the realm of appearance into mere representations, “the veil of Maya” or realm of illusion.70 In a passage from his Parerga, Schopenhauer had argued that Kant had no reason to assume an independent material component of experience because even the content of sensation is determined by the subject and exists only for it.71 Picking on this passage, Riehl finds its reasoning tendentious. Schopenhauer, he argues, failed to observe the strictly formal limits of sensibility, which can no more determine the details and determinacy of sensation than the categories of the understanding (431). All that depends on sensibility, apart from its a priori forms, is simply feeling, the awareness that we are passive and that things act upon us. Sensibility does not have it within itself, however, to determine when, where, how and which sensations appear to us.
Granted that there is an independent material component to experience, how does Riehl justify the assumption that it has for its cause things-in-themselves? This was the very assumption that Jacobi had found hard to justify according to the critical philosophy, which expressly limits the category of causality to experience. If things-in-themselves are not in experience, then we transcend the limits of knowledge in assuming that things-in-themselves are the causes of appearances. Riehl’s response to this classic difficulty is to make a distinction between the principle and concept of causality (432). While the principle is indeed limited to experience, because it applies only to temporal sequences, the concept can be extended beyond experience. Here Riehl was relying on Kant’s important distinction between knowing and thinking according to the categories. The restriction of the categories to experience holds only for knowing but not thinking. While this distinction indeed goes some way towards obviating Jacobi’s difficulty, it does not go far enough for Riehl, who claims not only that we can think of things-in-themselves as the cause of experience, but also that we can know this.
It was probably because he was aware that this simple distinction did not go far enough that Riehl insisted that Kant’s justification for assuming the thing-in-itself did not lie in a causal inference (432). To arrive at the existence of things-in-themselves, Kant did not make an inference from effect (the given sensations of experience) to cause (things-in-themselves) but he simply analysed the content of experience itself. If we analyse our representations, then we find that they have a formal and material element, and that while the formal element arises from our mental activity, the material element has to arise from a source independent of it (433). This manoeuvre made it seem as if Kant’s method were purely phenomenological, limited to an analysis of the content of representation. Yet it too did not remove the sting of Jacobi’s difficulty, because it tacitly postulated some cause for the content of representations, a cause that lies outside and not inside them.
Riehl’s realist interpretation of things-in-themselves stood in stark contrast to the idealist interpretations of Cohen and Windelband, which attempted to formulate the thing-in-itself in strictly regulative terms as a limiting concept or goal of enquiry. Though Riehl never engages in explicit polemic against their interpretations, it is plain that he feels constantly challenged by them. The constant citations of texts for his realist interpretation were doubtless made to counter Cohen’s interpretation, of which Riehl was well aware.72 It is at least very striking that he addresses that textual passage that seems to provide the most compelling evidence for Cohen’s view: namely, Kant’s statement at the end of the ‘Noumena and Phenomena’ chapter that the concept of the noumenon is a mere limiting concept and that the division of the world into noumena and phenomena is inadmissable (B 310–311). Riehl deals with this passage by making an important distinction between a noumenon and thing-in-itself: the former is only a specific form of the latter. A noumenon is a distinct kind of intelligible entity, the object of an intellectual intuition. This is indeed a purely problematic concept, just as Kant tells us, because there is no evidence for the existence of such an object. The thing-in-itself, however, can be taken in another sense to mean the thing that is the basis of appearance, and in that sense its reality is not problematic at all, because we must assume the existence of such things to explain our experience.
Although Riehl advocates a realist interpretation of things-in-themselves, he also acknowledges that Kant’s concept is ultimately ambiguous. There is not only the thing-in-itself as the thing that appears to human sensibility, but also the thing-in-itself that is a pure noumenon, the thing that is created by an intellectual intuition (438). The reason for this ambiguity, Riehl explains, lies with Kant’s moral motivations: to save moral and religious faith, he postulated a noumenal realm completely distinct from phenomena. Riehl is just as anxious as Cohen and Windelband to remove this purely noumenal realm. He questions whether it really would provide the foundation for the moral and religious belief that Kant intends, given that it has a strictly hypothetical or problematic status. In basing moral and religious belief upon this realm Kant was making it rest on a mere logical possibility (435). “Can the empty possibility of a realm of transcendent things be the true support for our moral ideals, which are inescapable and demand realization?” (438), Riehl asks. He was convinced that realism alone could provide the proper foundation for ethics.73 But just how this is so he did not explain.
The meaning and purpose of philosophy in the modern world never ceased to concern Riehl, who thought about it until his last days. Some ten years after his Über Begriff und Form der Philosophie Riehl returned to the topic in his inaugural lecture in Freiburg, his 1883 Ueber wissenschaftliche und nichtwissenschaftliche Philosophie.74 This lecture is one of the classic statements of the neo-Kantian conception of philosophy, reaffirming unequivocally Fischer’s and Zeller’s standpoint expounded two decades earlier. Yet Riehl’s lecture takes into account something new and troubling, a problem that threatened the entire neo-Kantian programme. His response to this problem will force him to rethink that programme and redefine philosophy itself.
The Freiburg lecture shows Riehl at his most positivist. His chief message is that the positive sciences alone give us knowledge of the world, and that traditional philosophy should surrender all claims to such knowledge. What is philosophy? We are told that it is nothing but Greek science (18). That means that it was the primitive form of what we now know today as natural science, whose many different sub-disciplines have realized and surpassed all the wildest dreams of Greek philosophy. In short, philosophy, in its classical form, has become obsolete. This theme is hammered home constantly in Riehl’s lecture, whose first half is devoted to a withering critique of traditional philosophy.
Riehl’s first target is the foundationalist ideal of philosophy, its attempt to be systematic, to create a complete system derived from a single self-evident first principle (3, 8). This ideal proved to be impossible to realize. We cannot derive the concrete content of experience from first principles; and applying them to different kinds of content is only to force them into a straitjacket (4). The idea of a complete system should be reformulated as a regulative ideal, Riehl advises, so that it is a goal for future enquiry. But this ideal or goal, he insists, cannot be achieved by philosophy itself. Since all theoretical knowledge is acquired by the sciences themselves, they should take over the traditional systematic ideal of philosophy. Hence Riehl declares: “The true system of knowledge … is the totality of the sciences themselves.” (7).
Riehl also takes issue with the popular conception of philosophy as a worldview (Weltanschauung). This conception had been made popular by Dilthey, and it had been proposed as a substitute for and antidote to the positive sciences. A worldview is meant to be something more than a system of knowledge, because it attempts to provide us with an orientation towards the world, to address not only our intellects but also our souls (8–9). But even here, Riehl contends, traditional philosophy fails us. There are two elements to a worldview: an objective element, which involves knowledge of the world; and a subjective element, which contains a person’s attitudes or feelings about the world. But the objective element is provided best by the sciences themselves; and the subjective element is a matter of faith and personal experience, which is no matter for scientific discussion at all (10–12).
Given the obsolescence of traditional philosophy, either as a system of knowledge or a worldview, it would seem that Riehl is close to announcing the death of philosophy itself. But Riehl does not take this last drastic step, and in this respect he resists positivism. He attempts to give a definition of philosophy that provides it with a vocation and method distinct from the sciences. Philosophy is for Riehl first and foremost epistemology (Erkenntniswissenschaft) (38). Rather than directly investigating things, as the positive sciences do, it investigates the understanding that knows things (37). Its fundamental task is therefore an examination of the logic of the sciences themselves (38). Such a definition means that philosophy can maintain its independence from the positive sciences while also not competing with them. As epistemology, philosophy is still a form of knowledge, and indeed a science, but it does not attempt to be a form of knowledge or science about the world. It is a second-order knowledge, knowledge of knowledge, which is distinct from the first-order knowledge of the sciences themselves. Riehl does not shirk from the conclusion that his conception of philosophy essentially makes it an underlabourer to the sciences. Philosophy must abandon its old claim to stand above the sciences, and it must learn to stand below them, recognizing its more humble role of a servant (38).
The final message behind Riehl’s Freiburg lecture is that philosophy can survive in the modern world only as a footman to the sciences. The examination of the logic of the sciences ensures philosophy its autonomy and its claim to be a science; but it has to abandon its pretensions to be a system or worldview. That was, in essence, the same doctrine proclaimed by Fischer and Zeller in the 1860s. It was all very simple and very strategic, seeming to provide the ultimate solution to the obsolescence crisis.
So far, so good. Yet it was not really good enough. As Riehl could well see, the whole position had a deep fatal flaw. It saved one half of philosophy only at the price of forfeiting its most noble and important half: namely, the enquiry into human values. Philosophy had always been more than epistemology and logic; it had also been ethics, politics and aesthetics, the enquiry into the good, the just and beautiful. Its task was not only theoretical but also practical. Since antiquity, it had been central to philosophy to determine the basic goals of human life, to be an ars vivendi or a guide to life (Lebensführung) (50). In short, the definition of philosophy in terms of epistemology was simply too narrow, allowing no place for these traditional disciplines or the enquiry into values.
What was Riehl to do in the face of this difficulty? Should he abandon his narrow definition or one half of philosophy? To his credit, Riehl takes the former option. He decides to expand his original definition, so that there will now be two sides to philosophy. There will be not only the theoretical or wissenschaftliche side, which is logic and epistemology, but also the practical or nichtwissenschaftliche side, which treats ethics, politics and aesthetics. The practical side has the task of laying down “the plan for a truly human conduct of life” or a “teleology of human life” (51). This task is “non-scientific” because its ultimate aim is not to know but to achieve the good life. It not only describes values but also prescribes them, telling us how we should think, act and feel. Such is Riehl’s concession to this practical side of philosophy that he even regards it as its nobler side. If epistemology is below the positive sciences, ethics, politics and aesthetics stand above them (50).
Why did Riehl make this decision? Why did he not simply stick to his more narrow definition, leaving ethics, politics and aesthetics to the particular sciences and arts? Part of the answer is that Riehl was playing to the Zeitgeist, adapting to the new interests and tastes of his age. According to Heinrich Rickert, a close friend during his Freiburg years, Riehl had come to see in the early 1890s, after finishing his Der philosophische Kriticismus, that his own ideal of a scientific philosophy no longer suited the needs of the age, that it failed to address the interests of the youth, who longed for some spiritual guidance from philosophy.75 Now that religion was losing its authority and attraction, students were turning to philosophy. Since they could not find answers in epistemology and logic, they were turning towards philosophers like Nietzsche and Schopenhauer.
So Riehl, in the early 1890s, faced another uncomfortable choice: change with the times or become an irrelevance. Riehl moved with the times, and in no half-hearted or begrudging manner. His interests moved more towards ethics and aesthetics. In 1897 he published an essay on poetics,76 and one of the first monographs on Nietzsche.77 The greater attention to practical philosophy is most evident in Riehl’s 1904 introductory lectures on philosophy, which were published as Zur Einführung in die Philosophie der Gegenwart.78 Now Riehl solves the obsolescence crisis by stressing the role of philosophy as a guide to life. While he does not abandon his old view about the central role of epistemology, Riehl now gives pride of place and greater emphasis to the practical tasks of philosophy. However much the sciences take over the theoretical side of philosophy, they cannot compete with its practical side. The former critic of “worldviews” (Weltanschauungen) now becomes an enthusiast for “lifeviews” (Lebensanschauungen), whose chief function is to provide a general view of life and the basic values needed to get through it. Riehl’s lectures conclude with a long critical discussion of Schopenhauer’s and Nietzsche’s views on the value of life. The Einführung was Riehl’s chief attempt to address the new interests of the youth, and in that it proved to be very successful, going through six editions from 1904 to 1921.
Now that Riehl had given such importance to the practical side of philosophy he needed to provide it with a foundation no less than the theoretical side. The foundation for the theoretical side was easy: we simply refer the philosophers to the natural sciences, who should begin their work of logical analysis and commentary. But what about the practical side? The simple positivist answer is to refer the philosopher to the social sciences, to jurisprudence, history and sociology. But it is striking that Riehl never took this easy route. For he insists that the practical philosopher should be something of a moral legislator and guide. He does not simply describe the values embedded in social, political and legal life but he also prescribes them. “To discover values, and thus to create them, is the vocation of that philosophy that is not a science but a life view and guide to the spirit.” (195) Fitting that practical task, Riehl sometimes refers to Kant’s doctrine of ideas, which, he reminds us, is properly founded strictly on practical reason (168). But just how ideas are based on practical reason Riehl did not explain; and it is difficult to understand how his faith in Kantian ideas squared with his scepticism about the Kantian categorical imperative, which questioned its power to provide specific maxims for conduct (169). Just how far Riehl was from thinking through the foundation of practical philosophy becomes clear from his wavering about the logical status of value itself. He insisted that values are a matter of volition and feeling, and that they are not objects of knowledge (149); but he also stressed that values are not created but discovered, as if they were somehow facts in the world to be known (153).
In 1904 Riehl still had a long way to go towards a foundation for practical philosophy. Rickert informs us that, even in his final years, Riehl was willing, even struggling, to provide one.79 He planned to write a book on value theory, which he was going to call Kritik der allgemeine geltenden Werte. But it never came to that, because his powers were gradually fading. Though his plans were great, his flesh was weak. Riehl died November 21, 1924, never having completed his work on value theory. He left his conception of philosophy divided into theoretical and practical halves with no unifying force between them.
1 On Frischeisen-Köhler, Scholz and Spranger, see Volker Gerhardt, Reinhard Mehring and Jana Rindert Berliner Geist: Eine Geschichte der Berliner Universitätsphilosophie bis 1946 (Berlin: Akademic Verlag, 1999), pp. 153–154, 217–218, 229–236, 315–317. On Hönigswald, see Hans Ludwig Ollig, Der Neukantianismus (Stuttgart: Metzler, 1979), pp. 88–93.
2 On Riehl’s influence on Schlick, Feigl and Reichenbach, see Michael Heidelberger, ‘Kantianism and Realism: Alois Riehl (and Moritz Schlick)’, in The Kantian Legacy in Nineteenth-Century Science, eds Michael Friedman and Alfred Nordmann (Cambridge, MA: MIT Press, 2006), pp. 211–226.
3 See Heinrich Rickert, ‘Alois Riehl’, Logos 13 (1924/25), 162–185, p. 166.
4 See Erich Jaensch, ‘Zum Gedächtnis von Alois Riehl’, in Kant-Studien 30 (1925), i–xxxvi, p. xxi–xxii.
5 During his university days in Vienna, Riehl was the student of Robert Zimmermann, who in turn was the student of Franz Exner, who was a student of Herbart’s. Franz Exner and Karl Lott were especially responsible for importing Herbart into Austria. See Carl Siegel, Alois Riehl. Ein Beitrag zur Geschichte des Neukantianismus (Graz: Leuschner & Lubensky, 1932), p. 21.
6 See Alois Riehl, Moral und Dogma (Vienna: Carl Gerold, 1872), reprinted in Philosophische Studien aus Vier Jahrzehnten (Leizpig: Quelle & Meyer, 1925), pp. 61–90. On the content and reaction to this early writing, see Klaus Christian Köhnke, Entstehung und Aufsteig des Neukantianismus (Frankfurt: Suhrkamp, 1986), pp. 340–343.
7 See Alois Riehl, Der philosophische Kriticismus und seine Bedeutung für die positive Wissenschaft (Leipzig: Wilhelm Engelmann, 1876–1887). Volume I appeared in 1876; Volume II/1 in 1879; and Volume II/2 in 1887. Since Volume II appeared in two separate halves, eight years apart from one another, it is customary to refer to three volumes. Here, following Riehl’s own practice, we will designate the two parts of Volume II as II/1 and II/2. The work will be designated in footnotes with the abbreviations PK.
8 See the preface to Volume I, iv.
9 Alois Riehl, Der philosophische Kriticismus (Leipzig: Kroner, 1924–1926).
10 Review of Cohen’s Kant’s Theorie der Erfahrung, Philosophische Monatshefte 8 (1872), 212–215; and Riehl’s review of Windelband’s Über die Gewißheit, Philosophische Monatshefte 9 (1874), 292–296.
11 Rickert, ‘Alois Riehl’, in Logos XIII (1924/25), p. 172.
12 The only references to Riehl in Cohen’s writings is three short footnotes in the third edition of Kants Theorie der Erfahrung (Berlin: Cassirer, 1918), pp. 128, 567, 585. These concern minor technical matters.
13 Cohen, Kants Theorie der Erfahrung, p. 169.
14 Heinrich Maier, ‘Alois Riehl. Gedächtnisrede, gehalten am 24. Januar 1925’, Kant-Studien 31 (1926), 563–579, p. 573.
15 Klaus Christian Köhnke regards Riehl as a positivist. See Köhnke, Entstehung und Aufstieg, pp. 42, 375–376, 431.
16 See the ‘Vorrede’ to the first volume of Riehl, Der philosophische Kriticismus, p. iii.
17 See the ‘Vorrede’ to the first volume of Der philosophische Kriticismus, p. vi, and Riehl’s review of Dühring’s Kritische Geschichte der Philosophie, in Philosophische Monatshefte 11 (1875), 165–179.
18 See Riehl’s critical remarks on Avenarius in Zur Einführung in die Philosophie der Gegenwart, fünfte Auflage (Leipzig: Teubner, 1919), p. 212.
19 See Alois Riehl, ‘Logik und Erkenntnistheorie’, in Die Kultur der Gegenwart, Teil I, Abteilung VI, Systematische Philosophie, ed. Paul Hinneberg, Zweite durchgesehene Auflage (Leipzig: Teubner, 1908), pp. 73–102, esp. 92–94.
20 Riehl, ‘Logik und Erkenntnistheorie’, p. 94.
21 Michael Heidelberger, ‘Kantianism and Realism’, p. 246, maintains that one of the chief reasons for Riehl’s lapse into oblivion is that he did not “manage to connect his philosophy of science to the natural sciences, especially physics, of his day after about 1905.” While this would have indeed undermined Riehl’s prestige among positivist circles, it would not have been a problem for the larger public.
22 The best and only biographical sources on Riehl are the articles by Rickert, Maier, Jaensch and Siegel, all cited above. Siegel, though not a student of Riehl, had access to his manuscripts and personal contact with his widow; however, the biographical part of his study is very brief and sketchy.
23 Alois Riehl, Realistische Grundzüge. Eine philosophische Abhandlung der allgemeinen und nothwendigen Erfahrungsbegriffe (Graz: Leuschner & Lubensky, 1870). This tract was reprinted in Philosophische Studien aus Vier Jahrzehnten (Leipzig: Quelle & Meyer, 1925), pp. 1–60. All references in parentheses above are to the original edition.
24 I disagree entirely with Heinrich Rickert’s judgement that the early works do not represent his later position. See Rickert, ‘Alois Riehl’, in Logos XIII (1924/25), 162–185, p. 167. He says that the decisive change in Riehl’s development came with his study of Kant and the natural sciences, though there is plenty of evidence for that already in the Grundzüge.
25 Pace Steiger, Riehl, p. 27.
26 As Hegel described Schelling’s attempt to acquire knowledge of things-in-themselves immediately through an intellectual intuition. See Hegel’s preface to Phänomenologie des Geistes (Hamburg: Meiner, 1952), p. 26.
27 See Kant, Kritik der Urteilskraft, ‘Einleitung’, V, 183–184.
28 See Leibniz, Monadologie, §3.
29 In Volume II/2, 180–181, of Der philosophische Kriticismus, Riehl repudiates the panpsychic atomism of Haeckel and Nägeli, which he describes in similar terms to his own earlier doctrine. Riehl now argues that the very idea of feeling depends on that of consciousness, the very opposite of what he held in the Grundzüge.
30 Alois Riehl, Über Begriff und Form der Philosophie (Berlin: Carl Duncker, 1872). Reprinted in Philosophische Studien, pp. 90–175, 332–339. All references in parentheses above are to the original edition.
31 It is misleading to describe this tract as revealing a transition from Herbart to Kant. See Hans-Ludwig Ollig, Der Neukantianismus, p. 23. While Riehl is indeed more critical of Herbart, his debts to Kant are already apparent in his earlier work; and the later work also distances itself from Kant in ways uncharacteristic of Riehl’s Der philosophische Kriticismus.
32 Franz Brentano, Psychologie vom empirischen Standpunkt (Leipzig: Duncker & Humblot, 1874).
33 Wilhelm Dilthey, Ideen über eine Beschreibende und Zergliedernde Psychologie, in Sitzungsberichten der Berliner Akademie der Wissenschaften, (1894), 1309–1407. See Gesammelte Schriften (Stuttgart: Teubner, 1964), V, 139–240.
34 See Herbart, ‘Ueber die Möglichkeit und Nothwendigkeit Mathematik auf Psychologie anzuwenden’, in Sämtliche Werke, ed. Karl Kehrbach and Otto Flügel (Langensalza: Hermann Beyer & Söhne, 1887–1912) V, 91–122, 107.
35 Riehl, Realistische Grundzüge, pp. 1–2, already began with a defence of philosophy on these grounds. Riehl, Über Begriff und Form, pp. 49–56, takes this critique a step further. Riehl explains (p. 56) that this whole section, Section 9, ‘Zur Methodik überhaupt’, was written to counter objections against the scientific stature of philosophy.
36 It is likely that Riehl was influenced by Cohen. See Riehl, ‘Zur Aprioritätslehre’, his appreciative review of Kants Theorie der Erfahrung in Philosophische Monatshefte 8 (1872), 212–215. He also notes Cohen’s influence upon him in the preface to the first volume of Der philosophische Kriticismus, I, v. Köhnke discusses in more detail the influence of Cohen on Riehl in Entstehung und Aufstieg, pp. 351–356.
37 See Section 13, Riehl, ‘Die Geschichte der Philosophie in ihrer Bedeutung für die Philosophie’, pp. 84–87, and Section 14, Riehl, ‘Die Philosophie als Geschichte’, pp. 87–93.
38 Alois Riehl, Der philosophische Kriticismus und seine Bedeutung für die positive Wissenschaft (Leipzig: Engelmann, 1876). All references in parentheses above are to this edition. The preface is dated November 1875. Riehl indicates in the preface (p. vi) that the printing of the work had been completed “for a long time” (seit geraumer Zeit), but that its publication was delayed from “an unforeseen accident” (ein unvorhergesehenes Missgeschick). The composition of the work was therefore probably completed well before the autumn of 1875.
39 It is pushed into the background, though not completely pushed aside, because Riehl still writes of “eine Philosophie des Bewusstseins” that is not “a mere psychology and physiology” (v). This earlier formulation plays no role, however, in Riehl’s account of philosophy in Der philosophische Kriticismus.
40 See, for example, Köhnke, Entstehung und Aufstieg, p. 376.
41 See Riehl, Der philosophische Kriticismus, I, 79.
42 Riehl, Der philosophische Kriticismus, II/2, 42.
43 Riehl, Der philosophische Kriticismus, II/2, 133, 149–150.
44 See, for example, Riehl, Der philosophische Kriticismus I, 31 and II/2, 182.
45 See, for example, Siegel, Alois Riehl, p. 10. I also disagree with Michael Heidelberger’s claim, ‘Kantianism and Realism’, p. 233, that in Riehl’s main work “the Kantian element is comparatively limited”, and that Riehl’s interpretation was “very idiosyncratic and inventive”. One might regard Riehl’s interpretation in this light if one disagrees with it on textual and historical grounds; but the fact remains that Riehl himself saw his realism as the proper interpretation of Kant. We shall see in Section 8, how closely Riehl cleaved to Kant in some of the fundamental philosophical issues of his day.
46 On the background of Riehl’s interpretation, see Köhnke, Entstehung und Aufstieg, pp. 373–376.
47 See Riehl, Der philosophische Kriticismus, I, 61, 74, 78.
48 Ernst Cassirer, Substanzbegriff und Funktionsbegriff (Berlin: Cassirer, 1910).
49 Cassirer, Substanzbegriff und Funktionsbegriff, I, 21, 87. See also PK II/1, 243, 248, 257.
50 See Riehl’s statement of the general principles of his realism in Der philosophische Kriticismus, II/2, 152–153, 174, 190.
51 Riehl, Der philosophische Kriticismus, II/2, 174.
52 Cf. Riehl, Der philosophische Kriticismus I, 12, 337.
53 Riehl, Der philosophische Kriticismus, II/2, 128.
54 Riehl, Der philosophische Kriticismus, II/2, 130.
55 Riehl, Der philosophische Kriticismus, II/2, 128.
56 Riehl, Der philosophische Kriticismus, II/1, 64–65. Cf. I, 27–35.
57 PK I, 23, 31.
58 See the arguments in PK II/2, 32–44.
59 PK, II/2, 34.
60 See Chapter 4, Sections 5 and 6.
61 See PK II/2, 48–49. But see also I, 29–30, where Riehl cited the theory of evolution to explain the doctrine of specific nervous energies.
62 Kant, Prolegomena, IV, 293, 375.
63 Capitel 2: ‘Zeit und Raum’, Riehl, Der philosophische Kriticismus II/1, 79–187.
64 This is especially clear with regard to Riehl’s attitude towards the theory of specific nerve energies. Cf. Riehl, Der philosophische Kriticismus, I, 29–30 and II/1, 51–58.
65 Riehl, ‘Ueber das Verhältniss der psychischen Erscheinungen zu den materiellen Vorgängen’, Der philosophische Kriticismus II/2, 176–216.
66 Cf. II/2, 152–153, 174.
67 Riehl, ‘Die Methode der Vernunftkritik’, Der philosophische Kriticismus, pp. 315–447.
68 Kant, Prolegomena IV, 293, 337, 373, 375.
70 Schopenhauer, Die Welt als Wille und Vorstellung, Sämtliche Werke, Wolfgang von Löhneysen (Stuttgart: Insel, 1968), I, 48–49, §5.
71 Schopenhauer, ‘Fragmente zur Geschichte der Philosophie’, in Parerga, Sämtliche Werke, IV, 114–118. Riehl cites large extracts from this passage and comments upon it, Der philosophische Kriticismus, I, 429–431. I leave aside the question here whether Riehl’s interpretation of this passage is accurate and whether it holds for Schopenhauer’s position in general. The interpretation is interesting more for what it reveals about Riehl rather than Schopenhauer.
72 Riehl reviewed Cohen’s Kants Theorie der Erfahrung for the Philosophische Monatshefte 8 (1872), 212–215. Though Riehl praised the virtues of Cohen’s book, he also took issue with Cohen’s interpretation of the thing-in-itself, which he felt made Kant’s transcendental idealism into an absolute idealism (p. 215). Some six years later, in the preface to first volume of Der philosophische Kriticismus, Riehl acknowledges that he has made use of all recent Kant literature, and he especially mentions the stimulation he has received from the work of Cohen and Zimmermann (v). Riehl also makes an unnamed reference to Cohen on p. 423, which is probably to the passage he had taken issue with in his earlier review. On Cohen’s account of the thing-in-itself, see Chapter 12, Section 8.
73 See Riehl, Realistische Grundzüge, p. 63.
74 Alois Riehl, Ueber wissenschaftliche und nichtwissenschaftliche Philosophie. Eine akademische Antrittsrede (Tübingen: Mohr, 1883). All references in parentheses are to this edition.
75 Rickert, ‘Alois Riehl’, pp. 179–180. Rickert’s view is confirmed by Riehl’s 1913 Princeton lecture, ‘The Vocation of Philosophy at the Present Day’, in Lectures delivered in Connection with the Dedication of the Graduate College of Princeton University in October 1913 (Princeton, NJ: Princeton University Press, 1914), pp. 43–63, esp. p. 47. Rickert maintains (p. 172) that this turn towards practical philosophy became apparent after completing Der philosophische Kriticismus in 1887, therefore decades before the Princeton lecture.
76 Alois Riehl, ‘Bemerkungen zu dem Problem der Form in der Dichtkunst’, Vierteljahrschrift für wissenschaftlichen Philosophie 21 (1897), 283–306; reprinted in Philosophische Studien, pp. 266–303.
77 Alois Riehl, Friedrich Nietzsche. Der Künstler und der Denker (Stuttgart: Frommann, 1897). The book went through four editions.
78 Alois Riehl, Zur Einführung in die Philosophie der Gegenwart, fifth edition (Stuttgart: Teubner, 1919). All references are to this edition.
79 Rickert, ‘Alois Riehl’, p. 176.