If the mere mechanism of nature be assumed as the ground of explanation of its purposiveness, we cannot ask: what are things in the world there for? For according to such an idealistic system it is only the physical possibility of things (to think which as purposes would be mere subtlety without any Object) that is under discussion; whether we refer this form of things to chance or to blind necessity, in either case the question would be vain. If, however, we assume the purposive combination in the world to be real and to be [brought about] by a particular kind of causality, viz. that of a designedly-working cause, we cannot stop at the question: why have things of the world (organised beings) this or that form? why are they placed by nature in this or that relation to one another? But once an Understanding is thought that must be regarded as the cause of the possibility of such forms as are actually found in things, it must be also asked on objective grounds: Who could have determined this productive Understanding to an operation of this kind? This being is then the final purpose in reference to which such things are there.
I have said above that the final purpose is not a purpose which nature would be competent to bring about and to produce in conformity with its Idea, because it is unconditioned. For there is nothing in nature (regarded as a sensible being) for which the determining ground present in itself would not be always conditioned; and this holds not merely of external (material) nature, but also of internal (thinking) nature—it being of course understood that I only am considering that in myself which is nature. But a thing that is to exist necessarily, on account of its objective constitution, as the final purpose of an intelligent cause, must be of the kind that in the order of purposes it is dependent on no further condition than merely its Idea.
Now we have in the world only one kind of beings whose causality is teleological, i.e. is directed to purposes and is at the same time so constituted that the law according to which they have to determine purposes for themselves is represented as unconditioned and independent of natural conditions, and yet as in itself necessary. The being of this kind is man, but man considered as noumenon; the only natural being in which we can recognise, on the side of its peculiar constitution, a supersensible faculty (freedom) and also the law of causality, together with its Object, which this faculty may propose to itself as highest purpose (the highest good in the world).
Now of man (and so of every rational creature in the World) as a moral being it can no longer be asked: why (quem in finem) he exists? His existence involves the highest purpose to which, as far as is in his power, he can subject the whole of nature; contrary to which at least he cannot regard himself as subject to any influence of nature.—If now things of the world, as beings dependent in their existence, need a supreme cause acting according to purposes, man is the final purpose of creation; since without him the chain of mutually subordinated purposes would not be complete as regards its ground. Only in man, and only in him as subject of morality, do we meet with unconditioned legislation in respect of purposes, which therefore alone renders him capable of being a final purpose, to which the whole of nature is teleologically subordinated.[131]
§ 85. Of Physico-theology
Physico-theology is the endeavour of Reason to infer the Supreme Cause of nature and its properties from the purposes of nature (which can only be empirically known). Moral theology (ethico-theology) would be the endeavour to infer that Cause and its properties from the moral purpose of rational beings in nature (which can be known a priori).
The former naturally precedes the latter. For if we wish to infer a World Cause teleologically from the things in the world, purposes of nature must first be given, for which we afterwards have to seek a final purpose, and for this the principle of the causality of this Supreme Cause.
Many investigations of nature can and must be conducted according to the teleological principle, without our having cause to inquire into the ground of the possibility of purposive working with which we meet in various products of nature. But if we wish to have a concept of this we have absolutely no further insight into it than the maxim of the reflective Judgement affords: viz. if only a single organic product of nature were given to us, by the constitution of our cognitive faculty we could think no other ground for it than that of a cause of nature itself (whether the whole of nature or only this bit of it) which contains the causality for it through Understanding. This principle of judging, though it does not bring us any further in the explanation of natural things and their origin, yet discloses to us an outlook over nature, by which perhaps we may be able to determine more closely the concept, otherwise so unfruitful, of an Original Being.
Now I say that Physico-theology, however far it may be pursued, can disclose to us nothing of a final purpose of creation; for it does not even extend to the question as to this. It can, it is true, justify the concept of an intelligent World Cause, as a subjective concept (only available for the constitution of our cognitive faculty) of the possibility of things that we can make intelligible to ourselves according to purposes; but it cannot determine this concept further, either in a theoretical or a practical point of view. Its endeavour does not come up to its design of being the basis of a Theology, but it always remains only a physical Teleology; because the purposive reference therein is and must be always considered only as conditioned in nature, and it consequently cannot inquire into the purpose for which nature itself exists (for which the ground must be sought outside nature),—notwithstanding that it is upon the determinate Idea of this that the determinate concept of that Supreme Intelligent World Cause, and the consequent possibility of a Theology, depend.