§ 61. _Of the objective purposiveness of Nature_
We have on transcendental principles good ground to assume a subjective purposiveness in nature, in its particular laws, in reference to its comprehensibility by human Judgement and to the possibility of the connexion of particular experiences in a system. This may be expected as possible in many products of nature, which, as if they were devised quite specially for our Judgement, contain a specific form conformable thereto; which through their manifoldness and unity serve at once to strengthen and to sustain the mental powers (that come into play in the employment of this faculty); and to which therefore we give the name of _beautiful_ forms.
But that the things of nature serve one another as means to purposes, and that their possibility is only completely intelligible through this kind of causality--for this we have absolutely no ground in the universal Idea of nature, as the complex of the objects of sense. In the above-mentioned case, the representation of things, because it is something in ourselves, can be quite well thought _a priori_ as suitable and useful for the internally purposive determination of our cognitive faculties; but that purposes, which neither are our own nor belong to nature (for we do not regard nature as an intelligent being), could or should constitute a particular kind of causality, at least a quite special conformity to law,--this we have absolutely no _a priori_ reason for presuming. Yet more, experience itself cannot prove to us the actuality of this; there must then have preceded a rationalising subtlety which only sportively introduces the concept of purpose into the nature of things, but which does not derive it from Objects or from their empirical cognition. To this latter it is of more service to make nature comprehensible according to analogy with the subjective ground of the connexion of our representations, than to cognise it from objective grounds.
Further, objective purposiveness, as a principle of the possibility of things of nature, is so far removed from _necessary_ connexion with the concept of nature, that it is much oftener precisely that upon which one relies to prove the contingency of nature and of its form. When, _e.g._ we adduce the structure of a bird, the hollowness of its bones, the disposition of its wings for motion and of its tail for steering, _etc._, we say that all this is contingent in the highest degree according to the mere _nexus effectivus_ of nature, without calling in the aid of a particular kind of causality, namely that of purpose (_nexus finalis_). In other words, nature, considered as mere mechanism, could have produced its forms in a thousand other ways without stumbling upon the unity which is in accordance with such a principle. It is not in the concept of nature but quite apart from it that we can hope to find the least ground _a priori_ for this.