That it does not belong to Theology as a part thereof, although it may be made of the most important use therein, is self-evident. For it has as its objects, natural productions, and their cause, and although it refers at the same time to the latter as to a ground lying outside of and beyond nature (a Divine Author), yet it does not do this for the determinant but only for the reflective Judgement in the consideration of nature (in order to guide our judgement on things in the world by means of such an Idea as a regulative principle, in conformity with the human Understanding).
But it appears to belong just as little to Natural Science, which needs determinant and not merely reflective principles in order to supply objective grounds for natural effects. In fact, nothing is gained for the theory of nature or the mechanical explanation of its phenomena by means of its effective causes, by considering them as connected according to the relation of purposes. The exhibition of the purposes of nature in its products, so far as they constitute a system according to teleological concepts, properly belongs only to a description of nature which is drawn up in accordance with a particular guiding thread. Here Reason, no doubt, accomplishes a noble work, instructive and practically purposive in many points of view; but it gives no information as to the origin and the inner possibility of these forms, which is the special business of theoretical Natural Science. Teleology, therefore, as science, belongs to no Doctrine, but only to Criticism; and to the criticism of a special cognitive faculty, viz. Judgement. But so far as it contains principles a priori, it can and must furnish the method by which nature must be judged according to the principle of final causes. Hence its Methodology has at least negative influence upon the procedure in theoretical Natural Science, and also upon the relation which this can have in Metaphysic to Theology as its propaedeutic.
§ 80. Of the necessary subordination of the mechanical to the teleological principle in the explanation of a thing as a natural purpose
The privilege of aiming at a merely mechanical method of explanation of all natural products is in itself quite unlimited; but the faculty of attaining thereto is by the constitution of our Understanding, so far as it has to do with things as natural purposes, not only very much limited but also clearly bounded. For, according to a principle of the Judgement, by this process alone nothing can be accomplished towards an explanation of these things; and consequently the judgement upon such products must always be at the same time subordinated by us to a teleological principle.
It is therefore rational, even meritorious, to pursue natural mechanism, in respect of the explanation of natural products, so far as can be done with probability; and if we give up the attempt it is not because it is impossible in itself to meet in this path with the purposiveness of nature, but only because it is impossible for us as men. For there would be required for that an intuition other than sensuous, and a determinate knowledge of the intelligible substrate of nature from which a ground could be assigned for the mechanism of phenomena according to particular laws, which quite surpasses our faculties.
Hence if the naturalist would not waste his labour he must in judging of things, the concept of any of which is indubitably established as a natural purpose (organised beings), always lay down as basis an original organisation, which uses that very mechanism in order to produce fresh organised forms or to develop the existing ones into new shapes (which, however, always result from that purpose and conformably to it).
It is praiseworthy by the aid of comparative anatomy to go through the great creation of organised natures, in order to see whether there may not be in it something similar to a system and also in accordance with the principle of production. For otherwise we should have to be content with the mere principle of judgement (which gives no insight into their production) and, discouraged, to give up all claim to natural insight in this field. The agreement of so many genera of animals in a certain common schema, which appears to be fundamental not only in the structure of their bones but also in the disposition of their remaining parts,—so that with an admirable simplicity of original outline, a great variety of species has been produced by the shortening of one member and the lengthening of another, the involution of this part and the evolution of that,—allows a ray of hope, however faint, to penetrate into our minds, that here something may be accomplished by the aid of the principle of the mechanism of nature (without which there can be no natural science in general). This analogy of forms, which with all their differences seem to have been produced according to a common original type, strengthens our suspicions of an actual relationship between them in their production from a common parent, through the gradual approximation of one animal-genus to another—from those in which the principle of purposes seems to be best authenticated, i.e. from man, down to the polype, and again from this down to mosses and lichens, and finally to the lowest stage of nature noticeable by us, viz. to crude matter. And so the whole Technic of nature, which is so incomprehensible to us in organised beings that we believe ourselves compelled to think a different principle for it, seems to be derived from matter and its powers according to mechanical laws (like those by which it works in the formation of crystals).
Here it is permissible for the archaeologist of nature to derive from the surviving traces of its oldest revolutions, according to all its mechanism known or supposed by him, that great family of creatures (for so we must represent them if the said thoroughgoing relationship is to have any ground). He can suppose the bosom of mother earth, as she passed out of her chaotic state (like a great animal), to have given birth in the beginning to creatures of less purposive form, that these again gave birth to others which formed themselves with greater adaptation to their place of birth and their relations to each other; until this womb becoming torpid and ossified, limited its births to definite species not further modifiable, and the manifoldness remained as it was at the end of the operation of that fruitful formative power.—Only he must still in the end ascribe to this universal mother an organisation purposive in respect of all these creatures; otherwise it would not be possible to think the possibility of the purposive form of the products of the animal and vegetable kingdoms.[120] He has then only pushed further back the ground of explanation and cannot pretend to have made the development of those two kingdoms independent of the condition of final causes.
Even as concerns the variation to which certain individuals of organised genera are accidentally subjected, if we find that the character so changed is hereditary and is taken up into the generative power, then we cannot pertinently judge the variation to be anything else than an occasional development of purposive capacities originally present in the species with a view to the preservation of the race. For in the complete inner purposiveness of an organised being, the generation of its like is closely bound up with the condition of taking nothing up into the generative power which does not belong, in such a system of purposes, to one of its undeveloped original capacities. Indeed, if we depart from this principle, we cannot know with certainty whether several parts of the form which is now apparent in a species have not a contingent and unpurposive origin; and the principle of Teleology, to judge nothing in an organised being as unpurposive which maintains it in its propagation, would be very unreliable in its application and would be valid solely for the original stock (of which we have no further knowledge).
Hume[121] takes exception to those who find it requisite to assume for all such natural purposes a teleological principle of judgement, i.e. an architectonic Understanding. He says that it may fairly be asked: how is such an Understanding possible? How can the manifold faculties and properties that constitute the possibility of an Understanding, which has at the same time executive force, be found so purposively together in one Being? But this objection is without weight. For the whole difficulty which surrounds the question concerning the first production of a thing containing in itself purposes and only comprehensible by means of them, rests on the further question as to the unity of the ground of the combination in this product of the various elements [des Mannichfaltigen] which are external to one another. For if this ground be placed in the Understanding of a producing cause as simple substance, the question, so far as it is teleological, is sufficiently answered; but if the cause be sought merely in matter as an aggregate of many substances external to one another, the unity of the principle is quite wanting for the internally purposive form of its formation, and the autocracy of matter in productions which can only be conceived by our Understanding as purposes is a word without meaning.