order.
Again, the history of all science demonstrates that much of its progress consists in bringing to light problems. Lack of consciousness of problems, even more than lack of ability to solve them, is the characteristic of the non-scientific mind. Problems cannot be solved till they are seen and stated, and the work of the earlier psychologists consisted largely in this sort of work. Further, they were filled with the Zeitgeist of their age, the age of the eighteenth century and the Aufklärung, which found nothing difficult, which hated mystery and complexity, which believed with all its heart in principles, the simpler and more abstract the better, and which had the passion of completion. By this spirit, the psychologists as well as the other thinkers of the day were mastered, and under its influence they thought and wrote.
Thus their work was conditioned by the nature of science itself, and by the age in which they lived. This work they did, and left to us a heritage of problems, of terminology, and of principles which we are to solve, reject, or employ as best we may. And the best we can do is to thank them, and then go about our own work; the worst is to make them the dividing lines of schools, or settle in hostile camps according to their banners. We are not called upon to defend them, for their work is in the past; we are not called upon to attack them, for our work is in the future.
It will be of more use briefly to notice some of the movements and tendencies which have brought about the change of attitude, and created what may be called the "New Psychology."
Not the slightest of these movements has been, of course, the reaction of the present century, from the abstract, if clear, principles of the eighteenth, towards concrete detail, even though it be confused. The general failure of the eighteenth century in all but destructive accomplishment forced the recognition of the fact that the universe is not so simple and easy a matter to deal with, after all; that there are many things in earth, to say nothing of heaven, which were not dreamed of in the philosophy of clearness and abstraction, whether that philosophy had been applied along the lines of the state, society, religion, or science. The world was sated with system and longed for fact. The age became realistic. That the movement has been accompanied with at least temporary loss in many directions, with the perishing of ideals, forgetfulness of higher purpose, decay of enthusiasm, absorption in the petty, a hard contentedness in the present, or a cynical pessimism as to both present and future, there can be no doubt. But neither may it be doubted that the movement was a necessity to bring the Antæaus of humanity back to the mother soil of experience, whence it derives its strength and very life, and to prevent it from losing itself in a substanceless vapor where its ideals and purposes become as thin and watery as the clouds towards which it aspires.
Out of this movement and as one of its best aspects came that organized, systematic, tireless study into the secrets of nature, which, counting nothing common or unclean, thought no drudgery beneath it, or rather thought nothing drudgery,-- that movement which with its results had been the great revelation given to the nineteenth century to make. In this movement psychology took its place, and in the growth of physiology which accompanied it I find the first if not the greatest occasion of the development of the New Psychology.
It is a matter in every one's knowledge that, with the increase of knowledge regarding the structure and functions of the nervous system, there has arisen a department of science known as physiological psychology, which has already thrown great light upon psychical matters. But unless I entirely misapprehend the popular opinion regarding the matter, there is very great confusion and error in this opinion, regarding the relations of this science to psychology. This opinion, if I rightly gather it, is, that physiological psychology is a science which does, or at least claims to, explain all psychical life by reference to the nature of the nervous system. To illustrate: very many professed popularizers of the results of scientific inquiry, as well as laymen, seem to think that the entire psychology of vision is explained when we have a complete knowledge of the anatomy of the retina, of its nervous connection with the brain, and of the centre in the latter which serves for visual functions; or that we know all about memory if we can discover that certain brain cells store up nervous impressions, and certain fibres serve to connect these cells,-- the latter producing the association of ideas, while the former occasion their reproduction. In short, the commonest view of physiological psychology seems to be that it is a science which shows that some or all of the events of our mental life are physically conditioned upon certain nerve-structures, and thereby explains these events. Nothing could be further from the truth. So far as I know, all the leading investigators clearly realize that explanations of psychical events, in order to explain, must themselves be psychical and not physiological. However important such knowledge as that of which we have just been speaking may be for physiology, it has of itself no value for psychology. It tells simply what and how physiological elements serve as a basis for psychical acts; what the latter are, or how they are to be explained, it tells us not at all. Physiology can no more, of itself, give us the what, why, and how of psychical life, than the physical geography of a country can enable us to construct or explain the history of the nation that has dwelt within that country. However important, however indispensable the land with all its qualities is as a basis for that history, that history itself can be ascertained and explained only through historical records and historic conditions. And so psychical events can be observed only through psychical means, and interpreted and explained by psychical conditions and facts.
What can be meant, then, by saying that the rise of this physiological psychology has produced a revolution in psychology? This: that it has given a new instrument, introduced a new method,-- that of experiment, which has supplemented and corrected the old method of introspection. Psychical facts still remain psychical, and are to be explained through psychical conditions; but our means of ascertaining what these facts are and how they are conditioned have been indefinitely widened. Two of the chief elements of the method of experiment are variation of conditions at the will and under the control of the experimenter, and the use of quantitative measurement. Neither of these elements can be applied through any introspective process. Both may be through physiological psychology. This starts from the well-grounded facts that the psychical events known as sensations arise through bodily stimuli, and that the psychical events known as volitions result in bodily movements; and it finds in these facts the possibility of the application of the method of experimentation. The bodily stimuli and movements may be directly controlled and measured, and thereby, indirectly, the psychical states which they excite or express.
There is no need at this day to dwell upon the advantages derived in any science from the application of experiment. We know well that it aids observation by indefinitely increasing the power of analysis and by permitting exact measurement, and that it equally aids explanation by enabling us so to vary the constituent elements of the case investigated as to select the indispensable. Nor is there need to call attention to the especial importance of experiment in a science where introspection is the only direct means of observation. We are sufficiently aware of the defects of introspection. We know that it is limited, defective, and often illusory as a means of observation, and can in no way directly explain. To explain is to mediate; to connect the given fact with an unseen principle; to refer the phenomenon to an antecedent condition ,-- while introspection can deal only with the immediate present, with the given now. This is not the place to detail the specific results accomplished through this application of experiment to the psychological sphere; but two illustrations may perhaps be permitted: one from the realm of sensation, showing how it has enabled us to analyze states of consciousness which were otherwise indecomposable; and the other from that of perception, showing how it has revealed processes which could be reached through no introspective method.
It is now well known that no sensation as it exists in consciousness is simple or ultimate. Every color sensation, for example, is made up by at least three fundamental sensory quales, probably those of red, green, and violet; while there is every reason to suppose that each of these qualities, far from being simple, is compounded of an indefinite number of homogeneous units. Thus the 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
