Historically, material things were the first to be studied and described with scientific exactness. It is only natural, therefore, that the methods and assumptions which have been employed with conspicuous success by the physical sciences should be extended, tentatively at least, elsewhere. It is equally natural that protests should be raised, and the extension proclaimed by philosophers to be illegitimate--"impoverishing faith without enriching knowledge."[15] "To regard the course of the world as the development of some blind force which works on according to universal laws, devoid of insight and freedom, devoid of interest in good and evil, are we to consider this unjustifiable generalisation of a concept, valid in its own sphere, as the higher truth?"[16] It is not, however, likely that science will drop a generalisation, however "unjustifiable" in metaphysics, if it works in practice. The question is whether it does work; and that is plainly a question of fact, not a question of metaphysics. We want to know therefore, first, whether things moving in space are the only things with which we are acquainted in common experience; and, next, whether all the changes which take place within the range of scientific observation are or can be explained by the laws of mechanics. It is clear that, if the mechanical theory of science and of evolution is to be successfully maintained, both these questions must be answered in the affirmative. It is equally clear that, if we confine ourselves to the actual facts, both questions must be answered in the negative. Thoughts, ideas, conceptions, sensations, feelings, emotions are things of which we have experience at every moment of our waking lives; and none of them are things which occupy space or move in space. A thought is not a thing which can be measured by a foot-rule, as things in space can be; the greatness of an idea is not one which measures so many yards by so many; a conception has no cubic contents; a toothache cannot be put in a pair of scales, nor can any process of chemical analysis be applied to hope or fear. We find ourselves, therefore, in this dilemma: if the mechanical theory is true, and science can deal only with things moving in space, then psychology and sociology are not sciences, and their subject-matter never can be made amenable to scientific treatment. On the other hand, if psychology is a science, then science deals with things which do not move in space.