Note 172 — Chapter I · THE LOGICAL CHARACTER OF PSYCHOLOGICAL SCIENCE

Psychology is, of course, far from being the only branch of study which, in its present state, employs categories of both types. Compare the constant use made in biological evolutionary theories of the teleological ideas of, e.g., the “struggle for existence,” the “survival of the fittest,” “sexual selection,” etc., ideas bodily conveyed from Sociology and Psychology. As we have just seen, the precisians who object to this mixture of higher and lower categories in Psychology are in the awkward predicament of only being able to get rid of it there by accentuating its presence in Physiology and Biology. Where they go wrong is in exaggerating the amount of logical unity attributable to any body of inquiries which happens, in virtue of being pursued by the same men and with the same accessories, to be called by a common name. It would require only a slight further exaggeration to argue that since all branches of knowledge are alike knowledge, they must be all either exclusively mechanical or exclusively teleological. There is no reason in the nature of things why “Psychology” should not at a particular period in the growth of knowledge cover as wide a range of inquiries, with as much internal variety of aim and method, as, say “Mathematics.”