Our Understanding has then this peculiarity as concerns the Judgement, that in cognition by it the particular is not determined by the universal and cannot therefore be derived from it; but at the same time this particular in the manifold of nature must accord with the universal (by means of concepts and laws) so that it may be capable of being subsumed under it. This accordance under such circumstances must be very contingent and without definite principle as concerns the Judgement.
In order now to be able at least to think the possibility of such an accordance of things of nature with our Judgement (which accordance we represent as contingent and consequently as only possible by means of a purpose directed thereto), we must at the same time think of another Understanding, by reference to which and apart from any purpose ascribed to it, we may represent as necessary that accordance of natural laws with our Judgement, which for our Understanding is only thinkable through the medium of purposes.
In fact our Understanding has the property of proceeding in its cognition, e.g. of the cause of a product, from the analytical-universal (concepts) to the particular (the given empirical intuition). Thus as regards the manifold of the latter it determines nothing, but must await this determination by the Judgement, which subsumes the empirical intuition (if the object is a natural product) under the concept. We can however think an Understanding which, being, not like ours, discursive, but intuitive, proceeds from the synthetical-universal (the intuition of a whole as such) to the particular, i.e. from the whole to the parts. The contingency of the combination of the parts, in order that a definite form of the whole shall be possible, is not implied by such an Understanding and its representation of the whole. Our Understanding requires this because it must proceed from the parts as universally conceived grounds to different forms possible to be subsumed under them, as consequences. According to the constitution of our Understanding a real whole of nature is regarded only as the effect of the concurrent motive powers of the parts. Suppose then that we wish not to represent the possibility of the whole as dependent on that of the parts (after the manner of our discursive Understanding), but according to the standard of the intuitive (original) Understanding to represent the possibility of the parts (according to their constitution and combination) as dependent on that of the whole. In accordance with the above peculiarity of our Understanding it cannot happen that the whole shall contain the ground of the possibility of the connexion of the parts (which would be a contradiction in discursive cognition), but only that the representation of a whole may contain the ground of the possibility of its form and the connexion of the parts belonging to it. Now such a whole would be an effect (product) the representation of which is regarded as the cause of its possibility; but the product of a cause whose determining ground is merely the representation of its effect is called a purpose. Hence it is merely a consequence of the particular constitution of our Understanding, that it represents products of nature as possible, according to a different kind of causality from that of the natural laws of matter, namely, that of purposes and final causes. Hence also this principle has not to do with the possibility of such things themselves (even when considered as phenomena) according to the manner of their production, but merely with the judgement upon them which is possible to our Understanding. Here we see at once why it is that in natural science we are not long contented with an explanation of the products of nature by a causality according to purposes. For there we desire to judge of natural production merely in a manner conformable to our faculty of judging, i.e. to the reflective Judgement, and not in reference to things themselves on behalf of the determinant Judgement. It is here not at all requisite to prove that such an intellectus archetypus is possible, but only that we are led to the Idea of it,—which contains no contradiction,—in contrast to our discursive Understanding which has need of images (intellectus ectypus) and to the contingency of its constitution.
If we consider a material whole, according to its form, as a product of the parts with their powers and faculties of combining with one another (as well as of bringing in foreign materials), we represent to ourselves a mechanical mode of producing it. But in this way no concept emerges of a whole as purpose, whose internal possibility presupposes throughout the Idea of a whole on which depend the constitution and mode of action of the parts, as we must represent to ourselves an organised body. It does not follow indeed, as has been shown, that the mechanical production of such a body is impossible; for to say so would be to say that it would be impossible (contradictory) for any Understanding to represent to itself such a unity in the connexion of the manifold, without the Idea of the unity being at the same time its producing cause, i.e. without designed production. This, however, would follow in fact if we were justified in regarding material beings as things in themselves. For then the unity that constitutes the ground of the possibility of natural formations would be simply the unity of space. But space is no real ground of the products, but only their formal condition, although it has this similarity to the real ground which we seek that in it no part can be determined except in relation to the whole (the representation of which therefore lies at the ground of the possibility of the parts). But now it is at least possible to consider the material world as mere phenomenon, and to think as its substrate something like a thing in itself (which is not phenomenon), and to attach to this a corresponding intellectual intuition (even though it is not ours). Thus there would be, although incognisable by us, a supersensible real ground for nature, to which we ourselves belong. In this we consider according to mechanical laws what is necessary in nature regarded as an object of Sense; but we consider according to teleological laws the agreement and unity of its particular laws and its forms—which in regard to mechanism we must judge contingent—regarded as objects of Reason (in fact the whole of nature as a system). Thus we should judge nature according to two different kinds of principles without the mechanical way of explanation being shut out by the teleological, as if they contradicted one another.
From this we are enabled to see what otherwise, though we could easily surmise it, could with difficulty be maintained with certainty and proved, viz. that the principle of a mechanical derivation of purposive natural products is consistent with the teleological, but in no way enables us to dispense with it. In a thing that we must judge as a natural purpose (an organised being) we can no doubt try all the known and yet to be discovered laws of mechanical production, and even hope to make good progress therewith; but we can never get rid of the call for a quite different ground of production for the possibility of such a product, viz. causality by means of purposes. Absolutely no human Reason (in fact no finite Reason like ours in quality, however much it may surpass it in degree) can hope to understand the production of even a blade of grass by mere mechanical causes. As regards the possibility of such an object, the teleological connexion of causes and effects is quite indispensable for the Judgement, even for studying it by the clue of experience. For external objects as phenomena an adequate ground related to purposes cannot be met with; this, although it lies in nature, must only be sought in the supersensible substrate of nature, from all possible insight into which we are cut off. Hence it is absolutely impossible for us to produce from nature itself grounds of explanation for purposive combinations; and it is necessary by the constitution of the human cognitive faculties to seek the supreme ground of these purposive combinations in an original Understanding as the cause of the world.
§ 78. Of the union of the principle of the universal mechanism of matter with the teleological principle in the Technic of nature
It is infinitely important for Reason not to let slip the mechanism of nature in its products, and in their explanation not to pass it by, because without it no insight into the nature of things can be attained. Suppose it admitted that a supreme Architect immediately created the forms of nature as they have been from the beginning, or that He predetermined those which in the course of nature continually form themselves on the same model. Our knowledge of nature is not thus in the least furthered, because we cannot know the mode of action of that Being and the Ideas which are to contain the principles of the possibility of natural beings, and we cannot by them explain nature as from above downwards (a priori). And if, starting from the forms of the objects of experience, from below upwards (a posteriori), we wish to explain the purposiveness, which we believe is met with in experience, by appealing to a cause working in accordance with purposes, then is our explanation quite tautological and we are only mocking Reason with words. Indeed when we lose ourselves with this way of explanation in the transcendent, whither natural knowledge cannot follow, Reason is seduced into poetical extravagance, which it is its peculiar destination to avoid.
On the other hand, it is just as necessary a maxim of Reason not to pass by the principle of purposes in the products of nature. For, although it does not make their mode of origination any more comprehensible, yet it is a heuristic principle for investigating the particular laws of nature; supposing even that we wish to make no use of it for explaining nature itself,—in which we still always speak only of natural purposes, although it apparently exhibits a designed unity of purpose,—i.e. without seeking beyond nature the ground of the possibility of these particular laws. But since we must come in the end to this latter question, it is just as necessary to think for nature a particular kind of causality which does not present itself in it, as the mechanism of natural causes which does. To the receptivity of several forms, different from those of which matter is susceptible by mechanism, must be added a spontaneity of a cause (which therefore cannot be matter), without which no ground can be assigned for those forms. No doubt Reason, before it takes this step, must proceed with caution, and not try to explain teleologically every Technic of nature, i.e. every productive faculty of nature which displays in itself (as in regular bodies) purposiveness of figure to our mere apprehension; but must always regard such as so far mechanically possible. But on that account to wish entirely to exclude the teleological principle, and to follow simple mechanism only—in cases where, in the rational investigation of the possibility of natural forms through their causes, purposiveness shows itself quite undeniably as the reference to a different kind of causality—to do this must make Reason fantastic, and send it wandering among chimeras of unthinkable natural faculties; just as a mere teleological mode of explanation which takes no account of natural mechanism makes it visionary.
In the same natural thing both principles cannot be connected as fundamental propositions of explanation (deduction) of one by the other, i.e. they do not unite for the determinant Judgement as dogmatical and constitutive principles of insight into nature. If I choose, e.g. to regard a maggot as the product of the mere mechanism of nature (of the new formation that it produces of itself, when its elements are set free by corruption), I cannot derive the same product from the same matter as from a causality that acts according to purposes. Conversely, if I regard the same product as a natural purpose, I cannot count on any mechanical mode of its production and regard this as the constitutive principle of my judgement upon its possibility, and so unite both principles. One method of explanation excludes the other; even supposing that objectively both grounds of the possibility of such a product rested on a single ground, to which we did not pay attention. The principle which should render possible the compatibility of both in judging of nature must be placed in that which lies outside both (and consequently outside the possible empirical representation of nature), but yet contains their ground, i.e. in the supersensible; and each of the two methods of explanation must be referred thereto. Now of this we can have no concept but the indeterminate concept of a ground, which makes the judging of nature by empirical laws possible, but which we cannot determine more nearly by any predicate. Hence the union of both principles cannot rest upon a ground of explanation of the possibility of a product according to given laws, for the determinant Judgement, but only upon a ground of its exposition for the reflective Judgement.—To explain is to derive from a principle, which therefore we must clearly know and of which we can give an account. No doubt the principle of the mechanism of nature and that of its causality in one and the same natural product must coalesce in a single higher principle, which is their common source, because otherwise they could not subsist side by side in the observation of nature. But if this principle, objectively common to the two, which therefore warrants the association of the maxims of natural investigation depending on both, be such that, though it can be pointed to, it cannot be determinately known nor clearly put forward for use in cases which arise, then from such a principle we can draw no explanation, i.e. no clear and determinate derivation of the possibility of a natural product in accordance with those two heterogeneous principles. But now the principle common to the mechanical and teleological derivations is the supersensible, which we must place at the basis of nature, regarded as phenomenon. And of this, in a theoretical point of view, we cannot form the smallest positive determinate concept. It cannot, therefore, in any way be explained how, according to it as principle, nature (in its particular laws) constitutes for us one system, which can be cognised as possible either by the principle of physical development or by that of final causes. If it happens that objects of nature present themselves which cannot be thought by us, as regards their possibility, according to the principle of mechanism (which always has a claim on a natural being), without relying on teleological propositions, we can only make an hypothesis. Namely, we suppose that we may hopefully investigate natural laws with reference to both (according as the possibility of its product is cognisable by our Understanding by one or the other principle), without stumbling at the apparent contradiction which comes into view between the principles by which they are judged. For at least the possibility is assured that both may be united objectively in one principle, since they concern phenomena that presuppose a supersensible ground.
Mechanism, then, and the teleological (designed) Technic of nature, in respect of the same product and its possibility, may stand under a common supreme principle of nature in particular laws. But since this principle is transcendent we cannot, because of the limitation of our Understanding, unite both principles in the explanation of the same production of nature even if the inner possibility of this product is only intelligible [verständlich] through a causality according to purposes (as is the case with organised matter). We revert then to the above fundamental proposition of Teleology. According to the constitution of the human Understanding, no other than designedly-working causes can be assumed for the possibility of organised beings in nature; and the mere mechanism of nature cannot be adequate to the explanation of these its products. But we do not attempt to decide anything by this fundamental proposition as to the possibility of such things themselves.