What is here meant by purposive adaptation? Nothing but the consonance of percepts within a whole. But, since all percepts are based upon laws (ideas), which we discover by means of thinking, it follows that the orderly coherence of the members of a perceptual whole is nothing more than the ideal (logical) coherence of the members of the ideal whole which is contained in this perceptual whole. To say that an animal or a man is not determined by an idea floating in mid-air is a misleading way of putting it, and the view which the critic attacks loses its apparent absurdity as soon as the phrase is put right. An animal certainly is not determined by an idea floating in mid-air, but it is determined by an idea inborn in it and constituting the law of its nature. It is just because the idea is not external to the natural object, but is operative in it as its very essence, that we cannot speak here of adaptation to purpose. Those who deny that natural objects are determined from without (and it does not matter, in this context, whether it be by an idea floating in mid-air or existing in the mind of a creator of the world), are the very men who ought to admit that such an object is not determined by purpose and plan from without, but by cause and law from within. A machine is produced in accordance with a purpose, if I establish a connection between its parts which is not given in Nature. The purposive character of the combinations which I effect consists just in this, that I embody my idea of the working of the machine in the machine itself. In this way the machine comes into existence as an object of perception embodying a corresponding idea. Natural objects have a very similar character. Whoever calls a thing purposive because its form is in accordance with plan or law may, if he so please, call natural objects also purposive, provided only that he does not confuse this kind of purposiveness with that which belongs to a subjective human action. In order to have a purpose, it is absolutely necessary that the efficient cause should be a concept, more precisely a concept of the effect. But in Nature we can nowhere point to concepts operating as causes. A concept is never anything but the ideal nexus of cause and effect. Causes occur in Nature only in the form of percepts. Dualism may talk of cosmic and natural purposes. Wherever for our perception there is a nexus of cause and effect according to law, there the Dualist is free to assume that we have but the image of a nexus in which the Absolute has realised its purposes. For Monism, on the other hand, the rejection of an Absolute Reality implies also the rejection of the assumption of purposes in World and Nature. ADDITION TO THE REVISED EDITION (1918).