If these regulative principles of investigation be converted into constitutive principles of the possibility of Objects, they will run thus:
Proposition: All production of material things is possible according to merely mechanical laws.
Counter-proposition: Some production of material things is not possible according to merely mechanical laws.
In this latter aspect, as objective principles for the determinant Judgement, they would contradict each other; and consequently one of the two propositions must necessarily be false. We shall then, it is true, have an antinomy, but not of Judgement; there will be a conflict in the legislation of Reason. Reason, however, can prove neither the one nor the other of these fundamental propositions, because we can have a priori no determinant principle of the possibility of things according to mere empirical laws of nature.
On the other hand, as regards the first-mentioned maxims of a reflective Judgement, they involve no contradiction in fact. For if I say, I must judge, according to merely mechanical laws, of the possibility of all events in material nature, and consequently of all forms regarded as its products, I do not therefore say: They are possible in this way alone (apart from any other kind of causality). All that is implied is: I must always reflect upon them according to the principle of the mere mechanism of nature, and consequently investigate this as far as I can; because unless this lies at the basis of investigation, there can be no proper knowledge of nature at all. But this does not prevent us, if occasion offers, from following out the second maxim in the case of certain natural forms (and even by occasion of these in the whole of nature), in order to reflect upon them according to the principle of final causes, which is quite a different thing from explaining them according to the mechanism of nature. Reflection in accordance with the first maxim is thus not abrogated; on the contrary, we are told to follow it as far as we can. Nor is it said that these forms would not be possible in accordance with the mechanism of nature. It is only asserted that human Reason in following up this maxim and in this way could never find the least ground for that which constitutes the specific [character] of a natural purpose, although it would increase its knowledge of natural laws. Thus it is left undecided whether or not in the unknown inner ground of nature, physico-mechanical and purposive combination may be united in the same things in one principle. We only say that our Reason is not in a position so to unite them; and that therefore the Judgement (as reflective—from subjective grounds, not as determinant, in consequence of an objective principle of the possibility of things in themselves) is compelled to think a different principle from that of natural mechanism as the ground of the possibility of certain forms in nature.
§ 71. Preliminary to the solution of the above antinomy
We can in no way prove the impossibility of the production of organised natural products by the mere mechanism of nature, because we cannot see into the first inner ground of the infinite multiplicity of the particular laws of nature, which are contingent for us since they are only empirically known; and so we cannot arrive at the inner all-sufficient principle of the possibility of a nature (a principle which lies in the supersensible). Whether therefore the productive faculty of nature is sufficient for that which we judge to be formed or combined in accordance with the Idea of purposes, as well as for that which we believe to require merely a mechanical system [Maschinenwesen] of nature; or whether there lies at the basis of things which we must necessarily judge as properly natural purposes, a quite different kind of original causality, which cannot be contained in material nature or in its intelligible substrate, viz. an architectonic Understanding—this is a question to which our Reason, very narrowly limited in respect of the concept of causality if it is to be specified a priori, can give no answer whatever.—But it is just as certain and beyond doubt that, in regard to our cognitive faculties, the mere mechanism of nature can furnish no ground of explanation of the production of organised beings. For the reflective Judgement it is therefore a quite correct fundamental proposition, that for that connexion of things according to final causes which is so plain, there must be thought a causality distinct from that of mechanism, viz. that of an (intelligent) cause of the world acting in accordance with purposes; but for the determinant Judgement this would be a hasty and unprovable proposition. In the first case it is a mere maxim of the Judgement, wherein the concept of that causality is a mere Idea, to which we by no means undertake to concede reality, but which we use as a guide to reflection, which remains thereby always open to all mechanical grounds of explanation and does not withdraw out of the world of Sense. In the second case the proposition would be an objective principle prescribed by Reason, to which the determinant Judgement must subject itself, whereby however it withdraws beyond the world of Sense into the transcendent and perhaps is led into error.
All appearance of an antinomy between the maxims of the proper physical (mechanical) and the teleological (technical) methods of explanation rests therefore on this; that we confuse a fundamental proposition of the reflective with one of the determinant Judgement, and the autonomy of the first (which has mere subjective validity for our use of Reason in respect of particular empirical laws) with the heteronomy of the second, which must regulate itself according to laws (universal or particular) given to it by the Understanding.
§ 72. Of the different systems which deal with the purposiveness of nature
No one has ever doubted the correctness of the proposition that judgement must be passed upon certain things of nature (organised beings) and their possibility in accordance with the concept of final causes, even if we only desire a guiding thread to learn how to cognise their constitution through observation, without aspiring to an investigation into their first origin. The question therefore can only be: whether this fundamental proposition is merely subjectively valid, i.e. is a mere maxim of our Judgement; or whether it is an objective principle of nature, in accordance with which, apart from its mechanism (according to the mere laws of motion), quite a different kind of causality attaches to it, viz. that of final causes, under which these laws (of moving forces) stand only as intermediate causes.