We have learnt from the great Kant that time, space, and causality are present in our consciousness according to their whole conformity to rule and the possibility of all their forms, quite independently of the objects that appear in them and form their content; or, in other words, they can be found just as well when we start from the subject as when we start from the object. Therefore we can with equal reason call them modes of perception or intuition of the subject, or qualities of the object in so far as it is object (with Kant, phenomenon, appearance), in other words, representation. We can also regard these forms as the indivisible boundary between object and subject. Therefore every object must of course appear in them, but the subject, independently of the appearing object, also possesses and surveys them completely. Now if the objects appearing in these forms are not to be empty phantoms, but are to have a meaning, they must point to something, must be the expression of something, which is not, like themselves, object, representation, something existing merely relatively, namely for a subject. On the contrary, they must point to something that exists without such dependence on something that stands over against it as its essential condition, and on its forms, in other words, must point to something that is not a representation, but a thing-in-itself. Accordingly, it could at any rate be asked: Are those representations, those objects, something more than and apart from representations, objects of the subject? Then what would they be in this sense? What is that other side of them that is toto genere different from the representation? What is the thing-in-itself? Our answer has been the will; but for the present I leave this answer aside.
Whatever the thing-in-itself may be, Kant rightly concluded that time, space, and causality (which we later recognized as forms of the principle of sufficient reason, this principle being the universal expression of the forms of the phenomenon) could not be its properties, but could come to it only after, and in so far as, it had become representation, in other words, belonged only to its phenomenon or appearance, not to it itself. For as the subject completely knows and constructs them out of itself, independently of all object, they must adhere to representation-existence as such, not to that which becomes representation. They must be the form of the representation as such, but not qualities of what has assumed that form. They must be already given with the mere contrast of subject and object (not in the concept but in the fact); consequently, they must be only the closer determination of the form of knowledge in general, the most universal determination whereof is that very contrast. Now what in turn is conditioned in the phenomenon, in the object, by time, space, and causality, since it can be represented only by their means, namely plurality through coexistence and succession, change and duration through the law of causality, and matter which is capable of being represented only on the assumption of causality, and finally everything again that can be represented only by their means—all this as a whole does not really belong to what appears, to what has entered the form of the representation, but only to this form itself. Conversely, however, that which in the phenomenon is not conditioned by time, space, and causality, cannot be referred to them, and cannot be explained according to them, will be precisely that in which the thing that appears, the thing-in-itself, becomes immediately manifest. It follows from this that the most complete capacity for being known, in other words, the greatest clearness, distinctness, and susceptibility to exhaustive investigation, will necessarily belong to what is peculiar to knowledge as such, and hence to the form of knowledge, not to that which in itself is not representation, not object, but which has become knowable only by entering these forms, in other words, has become representation or object. Hence only that which depends solely on being known, on being representation in general and as such (not on what becomes known and has only become representation), and which therefore belongs without distinction to all that is known, and on that account is found just as well when we start from the subject as when we start from the object—this alone will be able to afford us without reserve a sufficient, exhaustive knowledge that is clear to the very foundation. But this consists in nothing but those forms of every phenomenon of which we are a priori conscious, and which can be commonly expressed as the principle of sufficient reason. The forms of this principle relating to knowledge through perception (with which exclusively we are here concerned) are time, space, and causality. The whole of pure mathematics and pure natural science a priori are based on these alone. Therefore in these sciences only does knowledge meet with no obscurity; in these it does not encounter the unfathomable (the groundless, i.e., the will), that which cannot be further deduced. It is in this respect that Kant wanted, as we have said, to call those branches of knowledge, together with logic, specially and exclusively science. On the other hand, these branches of knowledge show us nothing more than mere connexions, relations, of one representation to another, form without any content. All content received by them, every phenomenon that fills those forms, contains something no longer completely knowable according to its whole nature, something no longer entirely explicable by something else, and thus something groundless, whereby knowledge at once loses its evidence and complete lucidity. But this thing that withdraws from investigation is precisely the thing-in-itself, that which is essentially not representation, not object of knowledge; but only by entering that form has it become knowable. The form is originally foreign to it, and it can never become completely one therewith, can never be referred to the mere form, and, as this form is the principle of sufficient reason, can therefore never be completely fathomed. Therefore, although all mathematics gives us exhaustive knowledge of that which in phenomena is quantity, position, number, in short, spatial and temporal relation; although etiology tells us completely about the regular conditions under which phenomena, with all their determinations, appear in time and space, yet, in spite of all this, teaches us nothing more than why in each case every definite phenomenon must appear just at this time here and just at this place now, we can never with their assistance penetrate into the inner nature of things. There yet remains something on which no explanation can venture, but which it presupposes, namely the forces of nature, the definite mode of operation of things, the quality, the character of every phenomenon, the groundless, that which depends not on the form of the phenomenon, not on the principle of sufficient reason, that to which this form in itself is foreign, yet which has entered this form, and now appears according to its law. This law, however, determines only the appearing, not that which appears, only the How, not the What of the phenomenon, only its form, not its content. Mechanics, physics, chemistry teach the rules and laws by which the forces of impenetrability, gravitation, rigidity, fluidity, cohesion, elasticity, heat, light, elective affinities, magnetism, electricity, and so on operate, in other words, the law, the rule, observed by these forces in regard to their entry into space and time in each case. But whatever we may do, the forces themselves remain qualitates occultae. For it is just the thing-in-itself which, by appearing, exhibits those phenomena. It is entirely different from the phenomena themselves, yet in its manifestation it is wholly subject to the principle of sufficient reason as the form of the representation, but it can never itself be referred to this form, and hence can never be thoroughly explained etiologically, or completely and ultimately fathomed. It is wholly comprehensible in so far as it has assumed this form, in other words, in so far as it is phenomenon, but its inner nature is not in the least explained by its thus being comprehensible. Therefore, the more necessity any knowledge carries with it, the more there is in it of what cannot possibly be otherwise thought or represented in perception—as, for example, space-relations; hence the clearer and more satisfying it is, the less is its purely objective content, or the less reality, properly so called, is given in it. And conversely, the more there is in it that must be conceived as purely accidental, the more it impresses us as given only empirically, then the more that is properly objective and truly real is there in such knowledge, and also at the same time the more that is inexplicable, in other words, the more that cannot be further derived from anything else.
Of course at all times an etiology, unmindful of its aim, has striven to reduce all organized life to chemistry or electricity, all chemistry, i.e., quality, in turn to mechanism (effect through the shape of the atoms), and this again sometimes to the object of phoronomy, i.e., time and space united for the possibility of motion, sometimes to the object of mere geometry, i.e., position in space (much in the same way as we rightly work out in a purely geometrical way the diminution of an effect according to the square of the distance and the theory of the lever). Finally, geometry can be resolved into arithmetic, which by reason of its unity of dimension is the most intelligible, comprehensible, and completely fathomable form of the principle of sufficient reason. Proofs of the method generally indicated here are the atoms of Democritus, the vortex of Descartes, the mechanical physics of Lesage which, towards the end of the eighteenth century, attempted to explain chemical affinities as well as gravitation mechanically from impact and pressure, as may be seen in detail from Lucrèce Neutonien; Reil’s form and combination as the cause of animal life also tend in this direction. Finally, crude materialism, raked up once more in the middle of the nineteenth century and from ignorance fancying itself to be original, is entirely of this nature. First of all, stupidly denying vital force, it tries to explain the phenomena of life by physical and chemical forces, and these in turn by the mechanical operation of matter, the position, form, and motion of imagined atoms. Thus it would like to reduce all the forces of nature to thrust and counter-thrust as its “thing-in-itself.” According to it, even light is supposed to be the mechanical vibration or undulation of an imaginary ether postulated for this purpose. When this ether reaches the retina, it beats on it, and, for example, four hundred and eighty-three thousand million beats a second give red, seven hundred and twenty-seven thousand million beats violet, and so on. So those who are colour-blind are those who cannot count the beats, I suppose! Such crass, mechanical, Democritean, ponderous, and truly clumsy theories are quite worthy of people who, fifty years after the appearance of Goethe’s theory of colours, still believe in Newton’s homogeneous light, and are not ashamed to say so. They will learn that what is condoned in the child (Democritus) will not be forgiven in the man. One day they might even come to an ignominious end, but then everyone would slink away and pretend he had had nothing to do with them. Soon we shall have more to say about this false reduction of original natural forces to each other; but for the moment this is enough. Suppose this were feasible, then of course everything would be explained and cleared up, and in fact would be reduced in the last resort to an arithmetical problem; and that would then be the holiest thing in the temple of wisdom, to which the principle of sufficient reason would at last have happily conducted us. But all content of the phenomenon would have vanished, and mere form would remain. The “what appears” would be referred to the “how it appears,” and this “how” would be the a priori knowable, and so entirely dependent on the subject, and hence only for the subject, and so finally mere phantom, representation and form of the representation through and through; one could not ask for a thing-in-itself. Suppose this were feasible, then in actual fact the whole world would be derived from the subject, and that would be actually achieved which Fichte by his humbug sought to seem to achieve. But this will not do; phantasies, sophistications, castles in the air, have been brought into being in this way, but not science. The many and multifarious phenomena in nature have been successfully referred to particular original forces, and whenever this has been done, a real advance has been made. Several forces and qualities, at first regarded as different, have been derived from one another (e.g., magnetism from electricity), and thus their number has been reduced. Etiology will have attained its object when it has recognized and exhibited all the original forces of nature as such, and established their methods of operation, in other words, the rule by which, following the guidance of causality, their phenomena appear in time and space, and determine their position with regard to one another. But there will always remain over original forces; there will always remain, as an insoluble residuum, a content of the phenomenon which cannot be referred to its form, and which thus cannot be explained from something else in accordance with the principle of sufficient reason. For in everything in nature there is something to which no ground can ever be assigned, for which no explanation is possible, and no further cause is to be sought. This something is the specific mode of the thing’s action, in other words, the very manner of its existence, its being or true essence. Of course, of each particular effect of the thing a cause can be demonstrated, from which it follows that it was bound to act at that particular time and place, but never a cause of its acting in general and precisely in the given way. If it has no other qualities, if it is a mote in a sunbeam, it still exhibits that unfathomable something, at any rate as weight and impenetrability. But this, I say, is to the mote what man’s will is to a man; and, like the human will, it is in its inner nature not subject to explanation; indeed, it is in itself identical with this will. Of course, for every manifestation of the will, for every one of its individual acts at such a time and in such a place, a motive can be shown, upon which the act was necessarily bound to ensue on the presupposition of the man’s character. But no reason can ever be stated for his having this character, for his willing in general, for the fact that, of several motives, just this one and no other, or indeed any motive, moves his will. That which for man is his unfathomable character, presupposed in every explanation of his actions from motives, is for every inorganic body precisely its essential quality, its manner of acting, whose manifestations are brought about by impressions from outside, while it itself, on the other hand, is determined by nothing outside it, and is thus inexplicable. Its particular manifestations, by which alone it becomes visible, are subject to the principle of sufficient reason; it itself is groundless. In essence this was correctly understood by the scholastics, who described it as forma substantialis. (Cf. Suárez, Disputationes Metaphysicae, disp. XV, sect. 1.)
It is an error as great as it is common that the most frequent, universal, and simple phenomena are those we best understand; on the contrary, they are just those phenomena which we are most accustomed to see, and about which we are most usually ignorant. For us it is just as inexplicable that a stone falls to the ground as that an animal moves itself. As mentioned above, it was supposed that, starting from the most universal forces of nature (e.g., gravitation, cohesion, impenetrability), we could explain from them those forces which operate more rarely and only under a combination of circumstances (e.g., chemical quality, electricity, magnetism), and finally from these could understand the organism and life of animals, and even the knowing and willing of man. Men tacitly resigned themselves to starting from mere qualitates occultae, whose elucidation was entirely given up, for the intention was to build upon them, not to undermine them. Such a thing, as we have said, cannot succeed; but apart from this, such a structure would always stand in the air. What is the use of explanations that ultimately lead back to something just as unknown as the first problem was? In the end, do we understand more about the inner nature of these natural forces than about the inner nature of an animal? Is not the one just as hidden and unexplored as the other? Unfathomable, because it is groundless, because it is the content, the what of the phenomenon, which can never be referred to the form of the phenomenon, to the how, to the principle of sufficient reason. But we, who are here aiming not at etiology but at philosophy, that is to say, not at relative but at unconditioned knowledge of the nature of the world, take the opposite course, and start from what is immediately and most completely known and absolutely familiar to us, from what lies nearest to us, in order to understand what is known to us only from a distance, one-sidedly, and indirectly. From the most powerful, most significant, and most distinct phenomenon we seek to learn to understand the weaker and less complete. With the exception of my own body, only one side of all things is known to me, namely that of the representation. Their inner nature remains sealed to me and is a profound secret, even when I know all the causes on which their changes ensue. Only from a comparison with what goes on within me when my body performs an action from a motive that moves me, with what is the inner nature of my own changes determined by external grounds or reasons, can I obtain an insight into the way in which those inanimate bodies change under the influence of causes, and thus understand what is their inner nature. Knowledge of the cause of this inner nature’s manifestation tells me only the rule of its appearance in time and space, and nothing more. I can do this, because my body is the only object of which I know not merely the one side, that of the representation, but also the other, that is called will. Thus, instead of believing that I would better understand my own organization, and therefore my knowing and willing, and my movement on motives, if only I could refer them to movement from causes through electricity, chemistry, and mechanism, I must, in so far as I am looking for philosophy and not for etiology, first of all learn to understand from my own movement on motives the inner nature of the simplest and commonest movements of an inorganic body which I see ensuing on causes. I must recognize the inscrutable forces that manifest themselves in all the bodies of nature as identical in kind with what in me is the will, and as differing from it only in degree. This means that the fourth class of representations laid down in the essay On the Principle of Sufficient Reason must become for me the key to the knowledge of the inner nature of the first class, and from the law of motivation I must learn to understand the law of causality in its inner significance.
Spinoza (Epist. 62) says that if a stone projected through the air had consciousness, it would imagine it was flying of its own will. I add merely that the stone would be right. The impulse is for it what the motive is for me, and what in the case of the stone appears as cohesion, gravitation, rigidity in the assumed condition, is by its inner nature the same as what I recognize in myself as will, and which the stone also would recognize as will, if knowledge were added in its case also. In this passage Spinoza has his eye on the necessity with which the stone flies, and he rightly wants to transfer this to the necessity of a person’s particular act of will. On the other hand, I consider the inner being that first imparts meaning and validity to all necessity (i.e., effect from cause) to be its presupposition. In the case of man, this is called character; in the case of the stone, it is called quality; but it is the same in both. Where it is immediately known, it is called will, and in the stone it has the weakest, and in man the strongest, degree of visibility, of objectivity. With the right touch, St. Augustine recognized in the tendency of all things this identity with our willing, and I cannot refrain from recording his naive account of the matter: Si pecora essemus, carnalem vitam et quod secundum sensum ejusdem est amaremus, idque esset sufficiens bonum nostrum, et secundum hoc si esset nobis bene, nihil aliud quaereremus. Item, si arbores essemus, nihil quidem sentientes motu amare possemus: verumtamen id quasi APPETERE videremur, quo feracius essemus, uberiusque fructuosae. Si essemus lapides, out fluctus, aut ventus, aut flamma, vel quid ejusmodi, sine ullo quidem sensu atque vita, non tamen nobis deesset quasi quidam nostrorum locorum atque ordinis APPETITUS. Nam velut AMORES corporum momenta sunt ponderum, sive deorsum gravitate, sive sursum levitate nitantur: ita enim corpus pondere, sicut animus AMORE fertur quocunque fertur (De Civitate Dei, XI, 28).62
Further, it is worth noting that Euler saw that the inner nature of gravitation must ultimately be reduced to an “inclination and desire” (hence will) peculiar to bodies (in the 68th letter to the Princess). In fact, it is just this that makes him averse to the conception of gravitation as found in Newton, and he is inclined to try a modification of it in accordance with the earlier Cartesian theory, and thus to derive gravitation from the impact of an ether on bodies, as being “more rational and suitable for those who like clear and intelligible principles.” He wants to see attraction banished from physics as a qualitas occulta. This is only in keeping with the dead view of nature which, as the correlative of the immaterial soul, prevailed in Euler’s time. However, it is noteworthy in regard to the fundamental truth advanced by me, which even at that time this fine mind saw glimmering from a distance. He hastened to turn back in time, and then in his anxiety at seeing all the prevalent fundamental views endangered, sought refuge in old and already exploded absurdities.