From the causal point of view, we may look upon the formative changes as the necessary outcome of strictly causal principles, and we may suppose that they take place without respect to the final result. But the question before us is rather to explain, if possible, why the changes that take place are in so many cases useful ones. That they are not always useful must be admitted, that they sometimes are must be granted, and it is the latter alternative that has attracted special attention. Now it is undoubtedly the simplest solution to claim that the scientist has nothing to do with the adaptiveness of the response, that his whole problem lies in a study of the causal phenomena involved in each process, but it is unquestionably true that scientists have not been satisfied to confine their hypotheses to this side of the question. The widespread interest in the theory of natural selection is, I think, due to the fact that it appears to offer an explanation of the formation of adaptive processes--not that it pretends to explain the origin of the adaptive structures or processes themselves, but that it seems to account for the adaptiveness of the fully formed product, _i.e._ the organism. For it will be seen that if only those forms (variations) survive that are useful, and survive either because the environment selects them (and exterminates the others), or because new forms that arise find a new place in nature where they can remain in existence, then the adaptiveness of the form to its surroundings would seem to be accounted for. In this case we can see how the causal processes that take place in the organism need have no causal connection with the environment,--except in the sense that the environment has acted as a selective agent, and appears, therefore, in the light of a teleological factor. But, as has been said before, the question is not so much that organisms _are_ adapted, as that organisms _respond adaptively_ to changes to which they can never have been subjected before. It is for the latter fact that a solution is to be sought.