Herbart.—Before the physiological school began to dominate the field, a very influential system of psychology was produced by Johann Friedrich Herbart (1776-1841). Reacting from the fashionable idealism of the day, Herbart made an attempt to construct a realistic doctrine which so far imitated the natural sciences as to be presented in the language of statics and dynamics. The original and most elaborate statement of the theory was cum bered with numerous mathematical formulae which had no real significance and were ignored even by the most faithful disciples. The fundamental thesis is that the soul is a real quantity of energy, an idea which comes directly from Leibniz. Every experience demands expenditure of this energy, a perpetual effort of the soul to maintain its unity against the force of impressions. Since the total energy is always the same, formulae for the distribution of energy can be devised. As any one impression gains strength, others lose it. Thus there is a continual rise and fall of presenta tions. When an idea first claims attention it has least energy and is said to be below the threshold of consciousness : if it acquires energy it rises and is apperceived : it may then be reduced again to the subconscious region. The picturesque language of summits, arches and wavecrests doubtless assisted to make Herbart popular. The fusion and complication of the elements served to explain the variety of mental states. Above all the Herbartian scheme gave new meaning to the ideas of attention and learning. Like his contemporary Beneke, Herbart had a sense for the pragmatic value of psychology. They both took a direct interest in the pro cesses of education and Herbart became almost a gospel for gener ations of teachers. The principle of connecting ideas so that new material could derive strength from ideas already present in the mind and the use of existing knowledge as the instrument by which to assimilate and "apperceive" new information were sources of inspiration to teachers. Among Herbart's numerous works the most important were the Lehrbuch der Psychologie (1816), the essay De Attentionis Measure (1822) and Psychologie als Wissenschaft neu gegrundet auf Erfahrung, Metaphysik and Mathematik (1824). Some of the best known writers of the Her bartian school were M. W. Drobisch, Theodor Waitz and W. F. Volkmann. Waitz in his Anthropologie der Naturvolker (1859) initiated a new development and directed attention to the field of racial psychology which occupies an important place in the litera ture of psychology after 186o.
In spite of its many good qualities the work of Herbart definitely belongs to the old tradition which had its chief affinities with the philosophical doctrines of the soul. A new departure required a point of view which was radically different and this was supplied by the progress of physiology. The work of Sir Charles Bell in England (An Idea of a New Anatomy of the Brain, 1811), of Magendie (1822) and others culminated in the general physiology of Johannes Miiller (1835) and changed the whole direction of thought. The new interest centred upon the structure of the nervous system and the demonstration of reflex action. To appreciate the importance of these topics it is neces sary to remember that general psychology was at that time still essentially a study of the spirit of man rather than his organiza tion. In spite of the Cartesian tendency to animal automatism and the mechanistic character of some later theories, there was no body of scientific facts which could be used to build up an ade quate account of the conscious life. The Hegelian introspective methods were losing support. In France Comte openly rejected the whole procedure and was one of the first to adopt the stand point of behaviourism. There was little or no conception of the end to which their scattered impulses were leading, but the move ment gathered strength. The more speculative minds saw the importance of classifying many human actions as reflex: for this meant that a large part of a man's life was put beyond the boun daries of reason. About 1851 Claude Bernard, Brown-Sequard and Ludwig contributed in different ways to the doctrine that the constriction and dilatation of the blood vessels is governed by the action of the nerves belonging to the sympathetic system. The sympathetic system has some connection with the brain but is partly independent and cannot be regarded as under the control of reason: it is to a large degree self-regulating and for that reason is also called autonomic. The bodily changes which take place
in the regions where the sympathetic nerves operate affect the whole condition of the organism, and, since they are not a part of the voluntary activities, must be regarded as destroying the idea that psychic life is limited to the field of rational conduct. A speculative interpretation of these facts was given by Schopen hauer who taught that reason was secondary to will and that the dominant factor in life was to be found in the unconscious im pulses which belong to the organism before the cerebral growth makes it possible to have ideas. This philosophy of the Uncon scious was a premature attempt, but it served to make popular the view that outside the sphere of ideas there is a wide range of activities, and that impulse is more dynamic than thinking.
The group of experimentalists who gathered round Johannes Muller were responsible for the creation of a definite physiological psychology. MUller himself made important experiments on the phenomena of vision, on the action of the vocal chords and on colour contrast. He taught the doctrine of specific energies of the nervous system, believing that each class of nerves was limited to one kind of action. This view has been modified as it seems more likely that the nerve-terminals are the important factors in determining the nature of the sensation. But though not wholly accurate Miiller's view was important in making clearer the fact that every experience is conditioned partly by the stimulus and partly by the structure of the nervous system. It was necessary, therefore, to study these as correlated events and physiological psychology became the science of these correlations. Muller was the first to give a satisfactory explanation of binocular vision. He demonstrated the fact that there are points on the retina of each eye which correspond in such a way that an object stimulating two corresponding points is seen as one visual object. Contem porary with MUller was E. H. Weber who studied experimentally the sense of touch and of temperature. Weber's Law, one of the landmarks of modern psychology, was first stated in 1834. In 1846 the article on Der Tastsinn and des GemeingefiThl appeared in Wagner's Handworterbuch der Physiologie. The formula known as Weber's law was derived from experiments which showed that if a stimulus increased by definite quantities the differences could only be perceived when the increase was a certain proportion of the previous quantity. In the case of hearing, for example, to obtain equal increases in the sounds as perceived it is necessary for the stimuli to increase by 4 (1, 4, etc.). The original state ment of the law has been modified in details but Weber established the general principle and was the author of that branch of psy chology which is called psychophysics. Weber's own work was a modest report of experiments. The notice which the facts and methods ultimately attracted was due to writings of Gustav Theodor Fechner. Fechner had considerable knowledge of science and was able to reduce his general theory of psychophysics to the forms of experimental research. He soon realized that the main points had already been stated by Weber. In fact it seems prob able that he did little more than revise and co-ordinate a number of existing formulae. The methods he used were (I) that of just noticeable differences, (2) of right and wrong cases, (3) of aver age error. The first had been used by Delezenne in 1826 and Weber in 1831 : the third by Steinheil in 1837 : the second by Vierordt in 1852. The particular merit of Fechner lay in the industry with which he investigated the working of these prin ciples. He gave direction and inspiration to a large number of workers who found in his methods a basis for exact experiments in the laboratory. His main work, Elemente der Psychophysik, was completed in 186o. G. E. MUller's work Zur Grundlegung der Psychophysik caused Fechner to write in 1882 a Revision which was to supersede the Elemente. Fechner also made researches in the field of aesthetics and was a pioneer in the study of aesthetic proportions.