9

THE EPISTEMOLOGIA IMAGINABILIS IN EIGHTEENTH-CENTURY SCIENCE AND PHILOSOPHY

THERE IS UNDOUBTEDLY one omission in our discussion of the Enlightenment so far, particularly as regards our aim of allowing historians to go beyond the very premises of what we have called the paradigm of the Centaur (according to Cassirer’s final version, in which the Enlightenment mainly coincides with the paradigm of Newtonian physics). More attention ought to be devoted to the final outcome of an ancient debate that for nearly two centuries has dominated discussions of historical knowledge within the ancient quarrel between the moral and natural sciences.

Indeed, we should reflect in greater depth on the fact that today our way of thinking of and defining science has radically changed compared even to the recent past. The change in science’s image and the revelation of the philosophers of science’s so-called epistemologia imaginabilis have been due especially to the research carried out in recent years by historians of science.1 This happened, however, only at the end of a difficult, centuries-old process, which can be only briefly summarized here.

Many things have changed since the day when the extraordinary results obtained by Kepler, Galileo, Descartes, and Newton effected a critical rethinking of all traditional forms of knowledge in the light of the scientific revolution. From Hobbes to Leibniz, to Hume and Diderot, many eminent scholars have engaged in the epistemological debate over extending the methods of the natural sciences to the study of human experience. For instance, in the course of the eighteenth century much hope was placed on the application of probability calculus to the social sciences. In his 1777 Essai d’arithmétique morale, Buffon theorized the existence in nature of “vérités de différents genres, des certitudes de différents ordres, des probabilités de différents degrés,”2 thus opening the way to Condorcet’s social mathematics, despite Diderot’s reservations about d’Alembert’s mathematical imperialism.

The idea of the unity of knowledge across all disciplines on the basis of scientific methodology reached its apex with Kant. However, we should not forget that at the start of the eighteenth century Giovan Battista Vico’s critique of Descartes, Locke, and Newton had laid the foundations for a different epistemological view of the various forms of knowledge, one based instead on the distinction between sciences of the spirit and sciences of nature.³ It is well known how, throughout the nineteenth century, historical knowledge was pitted against the prestige of scientific methodology. Countless scholars from every corner of Europe were questioning whether history should be considered a “science,” or whether it was more a form of “art,” closely related to rhetoric and literature.

In Italy, in 1893, Benedetto Croce wrote an essay with the emblematic title “La storia ridotta sotto il concetto generale dell’arte,” or “History Brought under the General Concept of Art.” The purpose of this brief study was to revisit this topic in light of the positivistic crisis at the end of the century, and to reply to an article written by Pasquale Villari in 1891, which had appeared also in German and French translation, in which the historian abruptly asked “Is History a Science?” The question seemed to have been convincingly settled once and for all by Droysen’s brilliant epistemological solution, set out in the three editions of his Historik (the last of which was published in 1882). However, this was before the so-called Methodenstreit broke out in Germany, with the intervention of Simmel, Dilthey, Rickert, and Weber, and revived the old dualism of the different forms of knowledge under new terms.⁴

In his famous handbook Droysen had clearly reasserted the primacy of Verstehen, that is to say of historical science as a form of knowledge that aims to achieve “understanding by means of investigation.”⁵ This was a kind of historical science that was mindful of the specificity of the moral world and of the liberty and will of man as the primary subject in history, and it stood in polemical contrast to attempts by positivists like Buckle to extend to history the methods and objectives of the natural sciences.⁶ The hermeneutical interpretative method and the traditional separation between sciences of the spirit and sciences of nature seemed to have won out also in the organization of university courses.

In fact, if one traces all the complex vicissitudes and echoes of the Methodenstreit across Europe, it will be easy to see how completely entangled all of the different positions and interpretations became as a result of the crisis of positivism and the start of the momentous revision of the epistemological foundations of the image of science. The traditional definition of science itself was called into doubt. This happened especially in France, following the work of Mach, Avenarius, Duhem, Boutroux, with Bergson’s and Le Roy’s harsh polemics against Poincaré at the end of the century. Once a static and normative matter of objective mathematical laws that were set once and for all and could be explained and predicted according to the rigorous deterministic model of Galileo and Newton’s rational mechanics, science came to be seen as a historically determined assemblage of hypotheses and theoretical explanations of a conventional and probabilistic nature. It needed to be verified empirically and then, if necessary, to be constantly “consumed” and replaced in the course of a process based on truths that were only ever partial and relative.

This undermined the nineteenth-century positivistic myth of science as absolute truth, dealing with laws that were universal, static, and eternal and that claimed to describe reality as the thing itself, objective and independent of the observer. That myth began now to crumble and was replaced by a “humanized” image of a science defined first and foremost by its method and practice, and by the creative role played by the researcher who formulates hypotheses and verifies each new theory in turn.7

Among the great historians, Marc Bloch was certainly the one who best understood the intellectual revolution that was at its most intense during the first few decades of the twentieth century, and the role that such a radically new conception of science could play in redefining and reviving the legitimacy also of historical knowledge. The real substance and originality of Bloch’s famous short work, Apologie pour l’histoire ou métier d’historien, which he wrote during the tragic years of World War II, lies in its passionate defense of the concrete bases of historical knowledge in the light of the heated epistemological debate on the nature of science that had taken place in the 1930s.⁸ In that context, Bloch’s text stands not only as a kind of closing chapter in the historians’ long-standing engagement with the natural sciences but also, and especially, as a fascinating manifesto in support of the unity of function of all sciences, and of their fundamental methodological and epistemological connection. The locus of this unity was the central position occupied by man, in accordance with the tenets of the Enlightenment and against the German dogma of the dualism of Geisteswissenschaften and Naturwissenschaften. More than half a century later, Bloch’s pages still come across as full of insights and of civic passion. While reading them, we should always keep in mind the so-called “crisis of reason” that profoundly affected intellectual life in Paris in the first few decades of the twentieth century. Nor should we forget the great debates organized by the Centre de synthèse, whose executive from 1925 included figures such as Rutherford, Einstein, and Volterra, alongside representatives of the humanities. And we should remember also the week-long conferences and seminars organized between 1929 and 1939 by Lucien Febvre, Paul Langevin, Abel Rey, and Henri Berr, on topics such as Evolution, Civilisation, Relativité, Théorie des quanta, Science et loi, and Statistique.9

Bloch certainly made good use of those very high-level meetings, encounters in which several Nobel-prize winners took part, and which had as their aim redefining the very idea of rationality and knowledge in every field of human knowledge. Their utility to Bloch went further, for he hoped to find here a way to go finally beyond what he saw as the historians’ centuries-old tendency to feel “rather small beside their colleagues in the laboratory,” i.e., before the protagonists in the field of experimental science. Bloch sets this out very clearly at the beginning of his essay, where he describes his work program. In relation to the hegemonic role played by the old positivistic model of nineteenth-century science, Bloch remarks:

Our mental climate has changed. The kinetic theory of gases, Einstein’s mechanics, and the quantum theory have profoundly altered that concept of science which, only yesterday, was unanimously accepted. They have not weakened it; they have only made it more flexible. For certainty, they have often substituted the infinitely probable; for the strictly measurable, the notion of the eternal relativity of measurement […] Hence, we are much better prepared to admit that a scholarly discipline may pretend to the dignity of a science without insisting upon Euclidian demonstrations or immutable laws of repetition. We find it far easier to regard certainty and universality as questions of degree. We no longer feel obliged to impose upon every subject of knowledge a uniform intellectual pattern, borrowed from natural science, since, even there, that pattern has ceased to be entirely applicable. We do not yet know what the sciences of man will be someday. We do know that in order to exist—and, it goes without saying, to exist in accordance with the fundamental laws of reason—they need neither disclaim nor feel ashamed of their own distinctive character.¹⁰

Consequently, the whole of the Apologie pour l’histoire is built around a point-by-point parallelism between the science of history and the new concept of natural sciences. Bloch’s stated objective was to stress the common epistemological and methodological matrix of all forms of knowledge, despite their individual languages and objects of investigation, a unity founded on their common ability to construct hypotheses and theories in order “to arrive at new certainties (or very strong probabilities), which are thenceforth duly proved.”¹¹

As Bloch pointed out, referring to Augustin Cournot, “[H]istorical criticism is like most other sciences of reality, except that it undoubtedly deals with a more subtle gradation of degrees.”¹² Like other sciences, it too aimed at the pursuit of objective truths, formulated hypotheses and conjectures in relation to specific problems, oriented its observations on the basis of theories to be proved, and studied the traces and signs of any phenomenon that was too elusive to be examined directly:

It matters little whether the original object is by its very nature inaccessible to the senses, like an atom whose trajectory is rendered visible in a Crookes tube, or whether through the effect of time it has only become so in the present, like the fern, rotting for thousands of years, whose imprint is left upon a lump of coal, or like those long-abandoned ceremonials which are painted and explained upon the walls of Egyptian temples. In either case, the process of reconstruction is the same, and every science offers a variety of examples of it.13

The “historian’s craft” and methods for the pursuit of truth, and the specific language that was employed in that process, must therefore be subjected to critical rethinking in the light of new advances in the fields of atomic physics and quantum mechanics, of the discovery of the indeterminacy principle, of the rejection of the concept of cause, and especially of the importance acquired by new probability-based prediction mechanisms, which rendered the traditional concept of scientific law and legality entirely obsolete. Many instances of this can be found within Marc Bloch’s slim volume, which was left unfinished and was published only posthumously in 1949, after the death of the author under Nazi torture. The most important thing for us now, however, is not so much to document his original defense of history’s epistemological status, but rather to register Bloch’s early awareness of the epistemological revolution that was taking place in those years of great discoveries and astounding interpretative innovations.¹⁴ That revolution was, in fact, redefining the very notion of science, taking as its starting point those very discoveries and the “crisis of classical reason” that they had directly fostered via Kant and Newton.

In 1934 Gaston Bachelard published in Paris Le Nouvel esprit scientifique. By means of psychological and philosophical analyses, Bachelard’s work underlined the importance to scientific activity of the scientist’s imagination. He also showed how the “scientific spirit” took a discontinuous form from the philosophical point of view, as it was constantly having to overcome the epistemological obstacles and obstructions created by the latest research. Frequent references to Heisenberg, de Broglie, Bohr, the Schola quantorum, and Einstein bolstered Bachelard’s thesis. His original philosophical view of the scientific enterprise was, thus, founded on his belief that with the theory of relativity the scientific spirit had become the judge of its own spiritual past.¹⁵

Also in 1934, but this time in Vienna, Karl R. Popper published his famous Logik der Forschung, which clearly addressed the crucial issue of those years, that of demarcation: What are the boundaries of science? Popper described empirical science as a “system of theories,” i.e., networks of hypotheses and universal statements with which to capture the “world,” so as to rationalize it and rule over it. The logics of knowledge and of scientific discovery, seen as a “theory of theories,” found its philosophical demarcation criteria in the falsifiability of those theories from every possible point of view: mathematical, logical, technical. That is to say, the criteria consisted in their self-correcting character, whereby the more a theory was falsifiable the higher its “scientificity” rate, because it meant that that theory explained more and so brought our thought closer to reality.

Popper thus entered into a fervent polemic with the conventionalist views of science, which at the time had a strong foothold in France and Italy, and especially with the sophisticated verificationist views of the Vienna Circle, whose members favored a form of logical empiricism whereby science manifested itself as a system of mutually consistent assertions and linguistic statements that were absolutely and irrevocably true.16 In contrast with that position, Popper claimed that his criterion of falsifiability had solved the classical problem of induction formulated by Hume. In 1970, he was again pointing out how, in order to move from facts to theories, our reason has to go through confutation and “falsification.” In fact, for decades following the first edition of his famous work, Popper persevered in his implacable polemic against logical neopositivism and the reduction of empirical science to enunciations and linguistic systems to be verified at the logical level. In Popper’s view, we should stop worrying about words and meanings and think instead about criticizable theories and reasoning, and about their validity.¹⁷

The other polemical target in Popper’s book, and also in most of his subsequent works, was obviously the “Copenhagen Geist,” that is to say the attack launched by the supporters of quantum mechanics against scientific determinism and the principle of an objective reality and of scientific legality, the position strenuously defended by Einstein.¹⁸ The metaphysical view of reality as fundamentally unknowable, which is implicit in Bohr’s complementarity principle, caused Popper to fear the onset of an irrationalistic drift within the very concept of empirical science. And yet, if we look closely, we realize that, despite the wealth of subjects with which it engages, Popper’s work seems strangely silent about important aspects of the wide debate that was taking place in those years in Europe. For instance, Popper never refers to the change in the images of science, in terms of the amount of importance now given to the historical context in which scientific discoveries took place and to science’s unavoidable relationship with the logical and philosophical context of justification. And yet this was a crucial issue that was beginning to fascinate historians of science, sociologists, philosophers, and scientists alike, all of whom were determined to go beyond the conclusions reached within the remit of logical empiricism.

The fact that times were now ripe for a change in this direction was confirmed by the publication in 1935 of Entstehung und Entwicklung einer wissenschaftlichen Tatsache, the masterwork of a Polish doctor-philosopher of Jewish origins, Ludwik Fleck. The title itself was intended as a challenge: How could a “scientific fact” be subject to “genesis” and “development”? A fact was a fact, and nothing more. And yet, by painstakingly tracing the modern concept of syphilis from the Renaissance to our day, Fleck revealed the changes that our way of seeing and interpreting this phenomenon had undergone in the course of the centuries through the elaboration of new theories. He showed also how each of these theories was variously influenced by astrology, political and religious beliefs, or by the needs and technological instruments of the time.

By examining the succession of different theories, from the earliest hypotheses that saw syphilis as a form of just “punishment,” to the discovery of the Wassermann reaction, Fleck was able to outline a whole new way of thinking about science, based on the importance of the historical context of each discovery, and not simply of its justification, as Popper and the members of the Vienna Circle had maintained, relying on logical models of analysis. In the creation of scientific knowledge, data could never be set apart from theories, and the latter were profoundly influenced by the “thought style” of the time and by the ruling “belief system.” Any scientific discovery was, in this sense, first and foremost the result of a change in a society’s “thought collective.”

Fleck’s inquiry into a theory’s historical development thus revealed that, in the final analysis, science was the result of an intellectual community at work, that is to say a public, not a private, fact. For the same reasons, rationality criteria were also a product of their time and of the scientists’ cultural horizon. In Fleck’s analysis, “[c]ognition is the most socially-conditioned activity of man.”19 “No medieval chemist could understand a modern law of chemistry in the same way that we do today and vice versa” (54). He pointed for example to the gap between the eighteenth century’s view of phosphorus and the modern idea of that element (128–133).

Thus the facts uncovered by Fleck, together with his historical analysis, completely invalidated the epistemological stance of those who favored an abstract logical and philosophical model of science. Fleck himself was very clear about this:

Biology taught me that a field undergoing development should be investigated always from the viewpoint of its past development. Who today would study anatomy without embryology? In exactly the same way epistemology without historical and comparative investigations is no more than an empty play on words or an epistemology of the imagination [epistemologia imaginabilis]. (20–21)

Fleck’s views were grounded in the work of such authors as Max Weber, Karl Mannheim, Lucien Lévy-Bruhl, Georg Simmel, and Wilhelm Wundt, and they followed from the theses of Gestaltpsychologie, according to which, from a logical and psychological point of view, observations made in isolation from their cultural premises did not make any sense. And yet, even though they admirably summarized an epistemological revolution that had been underway for quite some time, those pioneering ideas did not spread quickly. In fact, they remained the preserve of only a small number of specialists, and did not take a definitive hold in debates and general opinions until after World War II, and especially in the 1960s.20 It was only in 1962 with Thomas S. Kuhn’s short work, The Structure of Scientific Revolutions, that this epistemological revolution was finally complete, changing for good the traditional image of science inherited from nineteenth-century positivism.²¹

Kuhn placed at the center of his investigation the issue of scientific development and of the change wrought in our ideas of science by the historical model of analysis, as opposed to the traditional logical and philosophical model. He identified outright the realm of discovery with that of justification. The introduction to Kuhn’s work was significantly subtitled, “A Role for History.” And indeed Kuhn’s epistemological observations centered on the history of science and on the conflict among the different theories that had held sway over the course of time, and this emphasis remained a constant theme also in his subsequent works.²² In contrast to the image of scientific progress entertained by philosophers, science, as described by Kuhn, progressed historically through a series of revolutions, breakthroughs, and discontinuous events that represented real cultural transformations in our view of the world, changes that arose alongside new images of science. As he said, with an indirect reference to Wittgenstein’s Philosophical Investigations and to the Gestaltpsychologie movement, “[T]the marks on paper that were first seen as a bird are now seen as an antelope, or vice versa.”²³

Science was not a logical phenomenon of a cumulative and continuous kind. It was, rather, a product of historical and social factors that was discontinuous and controversial in nature. Its theories and images were diverse and mutually “incommensurable.” They were constant human approximations to a relative (certainly not an absolute) idea of truth: “[T]truth and falsity are uniquely and unequivocally determined by the confrontation of statement with fact” (80). As for development, this consisted in an alternation of phases of so-called “normal” science, which was dominated by winning theories that turned into pervasive and influential cognitive paradigms, interspersed with periods of crisis and revolution caused by problems within or without the scientific community, or by unexpected events, such as the discovery of oxygen, which set in motion Lavoisier’s chemical revolution.

For instance, one could not derive Newton’s science of dynamics from Einstein’s relativistic dynamics, nor would it be possible to find any logical connections in the move from geocentrism to heliocentrism, from phlogiston to oxygen, or from corpuscles to waves. Any talk of scientific progress in the traditional sense postulated a process of evolution towards a final purpose. But does nature have a purpose? In Kuhn’s words, “Any conception of nature compatible with the growth of science by proof is compatible with the evolutionary view of science developed here” (173).

From these considerations arose a lively intellectual debate on the foundations of knowledge, which is still open today, and which sees historians of science and philosophers of science on opposite sides. Having cast his lot with the former, Kuhn was unjustly accused of relativism, and of opening the door to a variety of irrationalistic drifts, forms of mysticism and epistemological anarchy, by postulating that paradigm changes and the very definition of science were determined first and foremost by historical reasons.24 In fact Kuhn’s book finally acknowledged that any absolute criteria for the validation of scientific theories had long disappeared, and that it did not make sense to continue to search for a mythical language that was entirely neutral and universal, a language that was purely descriptive and free from all interpretation.

In the general opinion of scholars, science is now seen everywhere as an assembly of conflicting theories and images of reality that certainly cannot be summed up as a logical totality of true propositions. Since Kuhn, it is no longer necessary to fight against the old distinction between Geisteswissenschaften and Naturwissenschaften in order to uphold the venerable thesis that originated with Descartes and was subsequently reformulated and updated by figures of the caliber of Marc Bloch, according to which there is a living unity across all sciences. This is a unity that transcends the differences in the specific languages of the different sciences and is based on a common research method founded on hypotheses and proof. The traditional nineteenth-century question, whether history is a science or not, has finally become meaningless.

Just as Bloch had predicted, the defense of historical knowledge in direct comparison with other disciplines has become much easier since the first few decades of the twentieth century. There is no longer an absolute truth that is the preserve of the natural sciences. All knowledge has been absorbed into the realm of human activity. First we saw a humanized theology, then came the humanization of science. In the light of these developments, historians of the Enlightenment ought to pay closer attention to the work and the results achieved by historians of science in the past few years. These scholars have brought down all barriers between the study of scientific theories and other cultural phenomena, and they have contributed significantly to the redefinition of the very concept of science, which is now based on the concept of truth as something that comes within the compass of human objectives and capabilities.25 But more than that, they have also prepared the groundwork for the definitive demise of the Centaur in the name and on behalf of the primacy of context and the historical method.

Today we no longer share Ernst Cassirer’s reductionist views on the identification of Enlightenment philosophy with the “paradigm of Newtonian physics” that formed the basis of Kantian rationalism. Historical research on the European fortune of Newton’s mechanistic universe has demonstrated the importance of social, political, and religious factors in helping that paradigm become established, and have highlighted the existence of other, quite different images of science.²⁶ The study of the historical phenomenon of the scientific revolution in the West and its development over the course of the centuries has unveiled both points of contact with, and significant points of divergence from the development and objectives of the Enlightenment movement.

Over the course of the eighteenth century, modern science underwent several crucial transformations, as it became an institution and acquired definitive legitimacy as a new form of knowledge. Significant changes also occurred in the mechanisms of formation and professionalization of its protagonists which were based on a corporate logic in the style of the Ancien Régime, a style that, paradoxically, contributed to its success despite the fact that that logic represented an antiquated view of society and its institutions. The old natural philosophers turned into modern scientists, along the lines of the Royal Society’s privatist model. At the same time, Parisian dilettantes became prestigious and privileged exponents of the corps savant, on the model of the Académie des Sciences. It was these kinds of transformations that gave rise to the first truly international scientific community.²⁷ Further developments contributed to what has been called “the triumph of sciences” in Europe. These included the rise of an extensive academic circuit, mostly financed by individual governments, a system of gazettes and scientific journals that kept public opinion abreast of new developments, and the establishment of a common language and shared practices, as well as the creation of a historical identity of the world of science through academic memoirs and the commemoration of famous scientists. Science became a global phenomenon à la mode, thanks to events such as the success of the Montgolfier brothers’ hot-air balloons, the chemical revolution brought about by Lavoisier and Priestley, Volta’s electricity, the new rational mechanics of Lagrange, and Spallanzani’s discoveries.²⁸

However, it was a mixed triumph, marked by conflict and furious clashes. It called into question the very identity of the modern scientist and brought up for the first time the crucial epistemological issue of demarcation: What is science? Who sets the criteria of truth? Who are scientists and how do you become one? How can we stop the powerful system of academies, with its Ancien-Régime style of corporate privileges, from transforming knowledge into a mechanism in the service of power and exclusion? These were the questions that were asked, for instance, by Brissot de Warville in his 1782 pamphlet, significantly entitled De la vérité. And he certainly was not alone. These issues sparked heated debate in the pages of gazettes and journals throughout Europe, echoing the old clashes between d’Alembert and Diderot, and between Voltaire and Rousseau. They were at the root of the frenzied struggle that broke out in the 1780s between Mesmer’s followers, Marat and Brissot, on the one hand, and, on the other, Condorcet and Vicq d’Azyr, who adhered instead to the Galilean and Newtonian paradigm represented by the triad numero, pondere et mensura.

This was a clash between two different ideas of the scientific profession—one based on vitalistic and organic views of nature in the wake of Francis Bacon, the other on the Newtonian paradigm and its physico-mathematical mechanicism. Far from signaling the end of the Enlightenment, as some writers have suggested, these two opposing views made clear the error of those who even today tend to identify the Enlightenment with a single scientific paradigm, and above all with a single criterion of rationality and demarcation.29

The fact that the world of the Enlightenment has dramatically split in two over these issues, to the point of postulating entirely different images of science, should make us pause. It is not by traveling once again down the foggy and imaginary path of the phenomenology of spirit that we will arrive at a clear understanding of what the Enlightenment truly was. This is amply demonstrated, on the one hand, by the centrality of man in relation to all his instruments of knowledge, including from an epistemological point of view, as is clearly illustrated by the tree of knowledge placed at the beginning of the Encyclopédie, with its basis in a new Enlightenment humanism. On the other hand, it is also evidenced by the necessity to exercise one’s reason freely in a critical and public way in every field, starting with the numerous challenges posed by the historical context.

Maybe the Centaur is now obsolete, even from a philosophical point of view. What is certain is that in the eyes of historians of science, who are set on realism and devoted to philological criticism, the Enlightenment does not entirely fit the pattern of a modernity modeled on the science of Newton’s Principia, as was maintained first by Hegel and then by others, all of whom were bent on linking the Enlightenment indissolubly and polemically with a specific image of modern science and with the subsequent positivistic period, regardless of the danger of anachronism.³⁰ In fact, as we shall try to demonstrate below, the Enlightenment comes across instead as a complex laboratory for a modernity that had to come to terms with the nooks and crannies of the historical context. It was a thorough-going process of cultural reorientation, similar to Kuhn’s scientific revolution, that affected our perception of the world and of man, with multiple, mutually-exclusive options. Here the dramatic and fascinating project of emancipating man through man on a cultural and political level came up against the challenges posed, in the first instance, by the historical context of Europe under the Ancien Régime.

But before examining this question in further detail we must make another detour. We need to look at the huge influence exercised by the historiographical tradition in which generations of Enlightenment scholars were raised and continued to work. With regard to that tradition, we must examine both what kind of political and ideological weight it brought to bear on historical discourse, and how methods of research were transformed in the course of the last century.