motives for this demand are various. The introduction of laboratory methods into psychology has given it a scientific savor, and the experimentalists are often ashamed of the company they are forced to keep. They have greater respect for the kind of work done by the natural scientists, who are apt to smile at the pretensions of the philosophers, and are therefore eager to flock with them. Or it is held that psychology is itself a natural science and belongs by right to that field. Mental processes cannot be understood without a knowledge of their physical and biological environment and must therefore be given over to men trained in these lines of research. Or the reasons for separation may be of a more practical nature. The psychologists may complain that the philosophers do not sympathize with their aims, that they do not comprehend their needs, and that association with them is apt to be detrimental to their interests. And here and there a philosopher may argue in favor of expelling empirical psychology, or at least psychophysics, from the philosophical union for similar reasons or because the expense of establishing laboratories should be borne by the scientific departments.
The proposed separation, however, would, in my opinion, be beneficial neither to philosophy nor to psychology itself. The affiliation is to the advantage of both parties. Of course the relation between these branches of knowledge is not to be one of absolute dependence on either side. By no means is psychology to be the handmaiden of metaphysics; the purpose cannot be to neglect the facts of mental experience and to offer an a priori system of psychology. Psychology must do its work along the general lines marked out for it in modern times, and continue to enjoy the independence which it has achieved within the domain of philosophy, and which, so far as I can see, no one dreams of curtailing. But independence here is not identical with disunion or even affiliation with another power. There are cogent reasons against such a change, and these I shall attempt to outline in what follows.
In the first place, we may argue against the affiliation of psychology with natural science on the ground that the subject matter of the former differs from that of the latter. Whatever may
