§ 64. _Of the peculiar character of things as natural purposes_
In order to see that a thing is only possible as a purpose, that is, to be forced to seek the causality of its origin not in the mechanism of nature but in a cause whose faculty of action is determined through concepts, it is requisite that its form be not possible according to mere natural laws, _i.e._ laws which can be cognised by us through the Understanding alone when applied to objects of Sense; but that even the empirical knowledge of it as regards its cause and effect presupposes concepts of Reason. This _contingency_ of its form in all empirical natural laws in reference to Reason affords a ground for regarding its causality as possible only through Reason. For Reason, which must cognise the necessity of every form of a natural product in order to comprehend even the conditions of its genesis, cannot assume such [natural] necessity in that particular given form. The causality of its origin is then referred to the faculty of acting in accordance with purposes (a will); and the Object which can only thus be represented as possible is represented as a purpose.
If in a seemingly uninhabited country a man perceived a geometrical figure, say a regular hexagon, inscribed on the sand, his reflection busied with such a concept would attribute, although obscurely, the unity in the principle of its genesis to Reason, and consequently would not regard as a ground of the possibility of such a shape the sand, or the neighbouring sea, or the winds, or beasts with familiar footprints, or any other irrational cause. For the chance against meeting with such a concept, which is only possible through Reason, would seem so infinitely great, that it would be just as if there were no natural law, no cause in the mere mechanical working of nature capable of producing it; but as if only the concept of such an Object, as a concept which Reason alone can supply and with which it can compare the thing, could contain the causality for such an effect. This then would be regarded as a purpose, but as a product of _art_, not as a natural purpose (_vestigium hominis video_).[106]
But in order to regard a thing cognised as a natural product as a purpose also--consequently as a _natural purpose_, if this is not a contradiction--something more is required. I would say provisionally: a thing exists as a natural purpose, if it is [although in a double sense][107] both _cause and effect of itself_. For herein lies a causality the like of which cannot be combined with the mere concept of a nature without attributing to it a purpose; it can certainly be thought without contradiction, but cannot be comprehended. We shall elucidate the determination of this Idea of a natural purpose by an example, before we analyse it completely.