nature, cannot without violence enter into the connection of any philosophical system except that one which makes a will the basis of the existence of every natural being; a will which accordingly expresses its nature and tendency not merely in the actions, but already in the form of the phenomenal organism. In the preceding chapter I have merely indicated the account which our system of thought gives of this subject, since I have already expounded it in the passage of the first volume referred to below, and with special clearness and fulness in “The Will in Nature,” under the rubric “Comparative Anatomy.”
The astounding amazement which is wont to take possession of us when we consider the endless design displayed in the construction of organised beings ultimately rests upon the certainly natural but yet false assumption that that adaptation of the parts to each other, to the whole of the organism and to its aims in the external world, as we comprehend it and judge of it by means of knowledge, thus upon the path of the idea, has also come into being upon the same path; thus that as it exists for the intellect, it was also brought about by the intellect. We certainly can only bring about something regular and conforming to law, such, for example, as every crystal is, under the guidance of the law and the rule; and in the same way, we can only bring about something designed under the guidance of the conception of the end; but we are by no means justified in imputing this limitation of ours to nature, which is itself prior to all intellect, and whose action is entirely different in kind from ours, as was said in the preceding chapter. It accomplishes that which appears so designed and planned without reflection and without conception of an end, because without idea, which is of quite secondary origin. Let us first consider what is merely according to rule, not yet adapted to ends. The six equal radii of a snowflake, separating at equal angles, are measured beforehand by no knowledge; but it is the simple tendency of the original will, which so exhibits itself to knowledge when knowledge appears. As now here the will brings about the regular figure without mathematics, so also without physiology does it bring about the form which is organised and furnished with organs evidently adapted to special ends. The regular form in space only exists for the perception, the perceptive form of which is space; so the design of the organism only exists for the knowing reason, the reflection of which is bound to the conceptions of end and means. If direct insight into the working of nature was possible for us, we would necessarily recognise that the wonder excited by teleology referred to above is analogous to that which that savage referred to by Kant in his explanation of the ludicrous felt when he saw the froth irresistibly foaming out of a bottle of beer which had just been opened, and expressed his wonder not that it should come out, but that any one had ever been able to get it in; for we also assume that the teleology of natural productions has been put in the same as it comes out for us. Therefore our astonishment at design may likewise be compared to that which the first productions of the art of printing excited in those who considered them under the supposition that they were works of the pen, and therefore had to resort to the assumption of the assistance of a devil in order to explain them. For, let it be said again, it is our intellect which by means of its own forms, space, time, and causality, apprehends as object the act of will, in itself metaphysical and indivisible, which exhibits itself in the phenomenon of an animal, – it is our intellect which first produces the multiplicity and diversity of the parts, and is then struck with amazement at their perfect agreement and conspiring together, which proceeds from the original unity; whereby then, in a certain sense, it marvels at its own work.
If we give ourselves up to the contemplation of the indescribably and infinitely ingenious construction of any animal, even if it were only the commonest insect, lose ourselves in admiration of it, and it now occurs to us that nature recklessly exposes even this exceedingly ingenious and highly complicated organism daily and by thousands to destruction by accident, animal rapacity, and human wantonness, this wild prodigality fills us with amazement; but our amazement is based upon an ambiguity of the conceptions, for we have in our minds the human work of art which is accomplished by the help of the intellect and by overcoming a foreign and resisting material, and therefore certainly costs much trouble. Nature's works, on the contrary, however ingenious they may be, cost her absolutely no trouble; for here the will to work is already the work itself, since, as has already been said, the organism is merely the visibility of the will which is here present, brought about in the brain.
In consequence of the nature of organised beings which has been set forth, teleology, as the assumption of the adaptation of every part to its end, is a perfectly safe guide in considering the whole of organised nature; on the other hand, in a metaphysical regard, for the explanation of nature beyond the possibility of experience, it must only be regarded as valid in a secondary and subsidiary manner for the confirmation of principles of explanation which are otherwise established: for here it belongs to the problems which have to be given account of. Accordingly, if in some animal a part is found of which we do not see any use, we must never venture the conjecture that nature has produced it aimlessly, perhaps trifling, or out of mere caprice. Certainly it is possible to conceive something of this kind under the Anaxagorean assumption that the disposition of nature has been brought about by means of an ordering understanding, which, as such, obeys a foreign will; but not under the assumption that the true inner being (i. e., outside of our idea) of every organism is simply and solely its own will; for then the existence of every part is conditioned by the circumstance that in some way it serves the will which here lies at its foundation, expresses and realises some tendency of it, and consequently in some way contributes to the maintenance of this organism. For apart from the will which manifests itself in it, and the conditions of the external world under which this has voluntarily undertaken to live, for the conflict with which its whole form and disposition is already adapted, nothing can have influenced it and determined its form and parts, thus no arbitrary power, no caprice. On this account everything in it must be designed; and therefore final causes (causæ finales) are the clue to the understanding of organised nature, as efficient causes (causæ efficientes) are the clue to the understanding of unorganised nature. It depends upon this, that if in anatomy or zoology, we cannot find the end or aim of an existing part, our understanding receives a shock similar to that which it receives in physics from an effect whose cause remains concealed; and as we assume the latter as necessary, so also we assume the former, and therefore go on searching for it, however long we may already have done so in vain. This is, for example, the case with the spleen, as to the use of which men never cease inventing hypotheses, till some day one shall have proved itself correct. So is it also with the large spiral-formed teeth of the babyroussa, the horn-shaped excrescences of certain caterpillars, and more of the like. Negative cases are also judged by us according to the same rule; for example, that in a class which, as a whole, is so uniform as that of lizards, so important a part as the bladder is present in many species, while it is wanting in others; similarly that dolphins and certain cetacea related to them are entirely without olfactory nerves, while the rest of the cetacea and even fishes have them: there must be a reason which determines this.
Individual real exceptions to this universal law of design in organised nature have indeed been discovered, and with great surprise; but in these cases that exceptio firmat regulam applies, since they can be accounted for upon other grounds. Such, for example, is the fact that the tadpoles of the pipa toad have tails and gills, although, unlike all other tadpoles, they do not swim, but await their metamorphosis on the back of the mother; that the male kangaroo has the marsupial bones which in the female carry the pouch; that male mammals have breasts; that the Mus typhlus, a rat, has eyes, although very small ones, without any opening for them in the outer skin, which thus covers them, clothed with hair; and that the moles of the Apennines, and also two fishes —Murena cœcilia and Gastrobrauchus cœcus– are in the same case; of like kind is the Proteus anguinus. These rare and surprising exceptions to the rule of nature, which is otherwise so rigid, these contradictions with itself into which it falls, we must explain from the inner connection which the different kinds of phenomena have with each other, by virtue of the unity of that which manifests itself in them, and in consequence of which nature must hint at some thing in one, simply because another of the same type actually has it. Accordingly the male animal has a rudimentary form of an organ which is actually present in the female. As now here the difference of the sex cannot abolish the type of the species, so also the type of a whole order – for example, of the batrachia – asserts itself even where