simplest musical sensation has also been experimentally proved to be in reality not simple, but doubly compound. First, there is the number of qualitatively like units constituting it which occasion the pitch of the note, according to the relations of time in which they stand to each other; and second, there is the relation which one order of these units bears to other secondary orders, which gives rise to the peculiar timbre or tone-color of the sound; while in a succession of notes these relations are still further complicated by those which produce melody and harmony. And all this complexity occurs, be it remembered, in a state of consciousness which, to introspection, is homogeneous and ultimate. In these respects physiology has been to psychology what the microscope is to biology, or analysis to chemistry. But the experimental method has done more than reveal hidden parts, or analyze into simpler elements. It has aided explanation, as well as observation, by showing the processes which condition a psychical event. This is nowhere better illustrated than in visual perception. It is already almost a commonplace of knowledge that, for example, the most complex landscape which we can have before our eyes, is, psychologically speaking, not a simple ultimate fact, nor an impression stamped upon us from without, but is built up from color and muscular sensations, with, perhaps, unlocalized feelings of extension, by means of the psychical laws of interest, attention, and interpretation. It is, in short, a complex judgment involving within itself emotional, volitional, and intellectual elements. The knowledge of the nature of these elements, and of the laws which govern their combination into the complex visual scene, we owe to physiological psychology, through the new means of research with which it has endowed us. The importance of such a discovery can hardly be overestimated. In fact, this doctrine that our perceptions are not immediate facts, but are mediated psychical processes, has been called by Helmholtz the most important psychological result yet reached.
But besides the debt we owe Physiology for the method of experiment, is that which is due her for an indirect means of investigation which she has put within our hands; and it is this aspect of the case which has led, probably, to such misconceptions of the relations of the two sciences as exist. For while no direct conclusions regarding the nature of mental activities or their causes can be drawn from the character of nervous structure or function, it is possible to reason indirectly from one to the other, to draw analogies and seek confirmation. That is to say, if a certain nervous arrangement can be made out to exist, there is always a strong presumption that there is a psychical process corresponding to it; or if the connection between two physiological nerve processes can be shown to be of a certain nature, one may surmise that the relation between corresponding psychical activities is somewhat analogous. In this way, by purely physiological discoveries, the mind may be led to suspect the existence of some mental activity hitherto overlooked, and attention directed to its workings, or light may be thrown on points hitherto obscure. Thus it was, no doubt, the physiological discovery of the time occupied in transmission of a nervous impulse that led the German psychologists to their epoch-making investigations regarding the time occupied in various mental activities; thus, too, the present psychological theories regarding the relation of the intellectual and volitional tracts of minds were undoubtedly suggested and largely developed in analogy with Bell's discovery of the distinct nature of the sensory and motor nerves. Again, the present theory that memory is not a chamber hall for storing up ideas and their traces or relies, but is lines of activity along which the mind habitually works, was certainly suggested from the growing physiological belief that the brain cells which form the physical basis of memory do not in any way store up past impressions or their traces, but have, by these impressions, their structure so modified as to give rise to a certain functional mode of activity. Thus many important generalizations might be mentioned which were suggested and developed in analogy with physiological discoveries.
The influence of biological science in general upon psychology has been very great. Every important development in science contributes to the popular consciousness, and indeed to philosophy, some new conception which serves for a time as a most valuable category of classification and explanation. To biology is due the conception of organism. Traces of the notion are found long before the great rise of biological science, and, in particular, Kant has given a complete and careful exposition of it; but the great rôle which the "organic" conception has played of late is doubtless due in largest measure to the growth of biology. In psychology this conception has led to the recognition of mental life as an organic unitary process developing according to the laws of all life, and not a theatre for the exhibition of independent autonomous faculties, or a rendezvous in which isolated, atomic sensations and ideas may gather, hold external converse, and then forever part. Along with this recognition of the solidarity of mental life has come that of the relation in which it stands to other lives organized in society. The idea of environment is a necessity to the idea of organism, and with the conception of environment comes the impossibility of considering psychical life as an individual, isolated thing developing in a vacuum.
This idea of the organic relation of the individual to that organized social life into which he is born, from which he draws his mental and spiritual sustenance, and in which he must perform his proper function or become a mental and moral wreck, forms the transition to the other great influence which I find to have been at work in developing the New Psychology. I refer to the growth of those vast and as yet undefined topics of inquiry which may be vaguely designated as the social and historical sciences,-- the sciences of the origin and development of the various spheres of man's activity. With the development of these sciences has come the general feeling that the scope of psychology has been cabined and cramped till it has lost all real vitality, and there is now the recognition of the fact that all these sciences possess their psychological sides, present psychological material, and demand treatment and explanation at the hands of psychology. Thus the material for the latter, as well as its scope, have been indefinitely extended. Take the matter of language. What a wealth of material and of problems it offers. How did it originate; was it contemporaneous with that of thought, or did it succeed it; how have they acted and reacted upon each other; what psychological laws have been at the basis of the development and differentiation of languages, of the development of their structure and syntax, of the meaning of words, of all the rhetorical devices of language. Any one at all acquainted with modern discussions of language will recognize at a glance that the psychological presentation and discussion of such problems is almost enough of itself to revolutionize the old method of treating psychology. In the languages themselves, moreover, we have a mine of resources, which, as a record of the development of intelligence, can be compared only to the importance of the paleontological record to the student of animal and vegetable life.
But this is only one aspect, and not comparatively a large one, of the whole field. Folk-lore and primitive culture, ethnology and anthropology, all render their contributions of matter, and press upon us the necessity of explanation. The origin and development of myth, with all which it includes, the relation to the nationality, to language, to ethical ideas, to social customs, to government and the state, is itself a psychological field wider than any known to the previous century. Closely connected with this is the growth of ethical ideas, their relations to the consciousness and activities of the nation in which they originate, to practical morality, and to art. Thus I could go through the various spheres of human activity, and point out how thoroughly they are permeated with psychological questions and material. But it suffices to say that history in its broadest aspect is itself a psychological problem, offering the richest resources of matter.
Closely connected with this, and also influential in the development of the New Psychology, is that movement which may be described as the commonest thoughts of everyday life in all its forms, whether normal or abnormal. The cradle and the asylum are becoming the laboratory of the psychologist of the latter half of the nineteenth century. The study of children's minds, the discovery of their actual thoughts and feelings from babyhood up, the order and nature of the development of their mental life and the laws governing it, promises to be a mine of greatest value. When it was recognized that insanities are neither supernatural interruptions nor utterly inexplicable "visitations," it gradually became evident that they were but exaggerations of certain of the normal workings of the mind, or lack of proper harmony and co-ordination among these workings; and thus another department of inquiries, of psychical experiments performed by nature, was opened to us, which has already yielded valuable results.
