The work in which Leibniz made clear his opposition to Locke (Nouveaux essais sur l'entendement humain, 1704) was not pub lished until 1765. This explains the appearance in Germany of a vigorous but brief period of purely empirical work. Taken directly from English sources and constructed largely by translating the works of Locke and other British writers, this empiricism for a time changed the current of German thought. But experience was interpreted in terms of feeling rather than sensation. The German writers were most interested in recording their inner states : the diary with its intimate introspective entries became fashionable. The Berlin Academy became a centre of psychological activity and the ultimate product of much tentative discussion was the recognition of the "three-faculty" doctrine. Henceforth sensation, feeling and will were regarded as the three classes of mental states. Before this time only cognition and volition were recog nized: the feelings came in as obscure ideas. Several minor writers contributed to produce this result, but the most authori tative work was due to Tetens. Johann Nicolas Tetens (1736 1807) wrote his Philosophische Versuche fiber die menschliche Natur and ihre Entwickelung in 1777. This book has consider able historical significance. The speculative psychology of the period did not attract Tetens. Bonnet, the Swiss naturalist, had brought into vogue a "fibre psychology," in other words, a premature attempt to explain mental processes by associating each activity with a neural fibre and describing it in terms of the motion excited in the fibres. Tetens more correctly relied on the observation of experiences and his treatment of the subject is on the whole well-balanced and sound in its principles. Kant was well acquainted with the work of Tetens and derived from that source the psychological groundwork of his philosophy. The criti cal philosophy of Kant does not enter into a history of psychology, though its principles have had great influence on later theories, chiefly in the direction of eliminating from psychology the idea of the soul and confining attention to mental phenomena. The successors of Kant followed lines of thought that moved further away from the experimental basis, and consequently added noth ing of importance to psychology as a natural science. German idealism from Kant to Hegel (183o) was not concerned with the mind as understood by the empiricists but with the concept of a universal mind. In spite of the sterility of this doctrine so far as concerns the data of individual psychology, its tendency to look beyond the individual to the race and to the historical evolution of thought was the incentive which impelled the next generation to begin enquiries into folk-psychology and social psychology. But before this could become a distinctive field of work the spirit of the exact sciences had to be revived.
At the close of the eighteenth century the French were ad mittedly supreme in the sciences of anatomy and physiology. Their influence tended to restore psychology to its place among the sciences of the organism. The treatment of mental derange ments as natural conditions and not as possession by evil spirits was greatly advanced by the attitude of Pinel, a doctor in Paris. About the same time (1798) the treatment of defectives was put on a more rational basis. The idea of the mind as a mysterious occupant of the body was discarded : empirical philosophy and medical science combined to establish the idea that it was the product of the experiences which were supplied through the senses. This theory was responsible for the work of men like Itard (1774-1838) who definitely formulated the principles of re-educa tion for defectives, and others who began to study methods for training the deaf and dumb. A growing tendency to regard the mind as a group of functions dependent on the brain and in directly on the whole physical organism was given explicit form in the writing of Pierre Jean George Cabanis. Adopting the medical profession and training his mind not only on the modern literature but also on the works of Hippocrates, Cabanis became in effect the advocate of physiological psychology. The famous expression attributed to him, that the brain secretes thought as the liver secretes bile, was not a piece of materialistic cynicism but a vigor ous way of declaring that mental functions were always brain functions. Cabanis wrote a work entitled Rapports du physique et
du moral de l'homme (1789 and 1802) which is one of the modern classics on the relation of mind and body. In this field Cabanis was soon surpassed by Franz Josef Gall (1758-1828) an Austrian surgeon who deserved more recognition than he obtained. Reli gious fanaticism and political intrigue combined to suppress his efforts, but Gall established his reputation in Europe for un equalled knowledge of cerebral anatomy and his own work was the foundation of the doctrine of cerebral localization. Gall was unfortunate in having a pupil, Spurzheim, who was a charlatan. Spurzheim found an ally in George Combe of Edinburgh and their misguided zeal produced the literature of Phrenology, a fan tastic combination of bad anatomy with an absurd theory of faculties. In spite of the ill repute which this foolish theory of "bumps" brought on the excellent work of Gall, it is necessary to recognize that Gall's own work was very important and was known to the best anatomists of Europe. Gall knew the difference be tween the sensory and motor nerves and that they had different points of origin in the spinal cord. This important discovery, which ultimately made clear the nature of reflex action, was an nounced in England by Sir Charles Bell (1811), and was pre sumably the result of independent research.
In the first quarter of the nineteenth century psychology was not making much progress. In England the associationism of David Hartley was regarded as orthodox doctrine. Hartley came under the spell of Newton's work and proposed to explain all men tal phenomena by assuming that they were due to vibrations of the nerves and that these vibrations could be communicated by one nerve to another if the other had at any time been excited together with the first. This was obviously a theory of association stated in the language of Newtonian mechanics. Hartley's work, Observa tions on Man, His Frame, His Duty and His Expectations, was completed in 1746. It was a diffuse production and included the theory of vibrations, the theory of association and a considerable amount of comment on the Christian religion. Priestley, interested in all kinds of scientific work and inclined to atheism, saw the ad vantages of this associationism and produced in 1775 an edition which omitted everything else. In 180i a complete edition ap peared in England and this gave the theory a new lease of life. The development of British psychology was affected for a time by at tempts to break away from the strict principles of empiricism. Thomas Brown (died 1820) was inclined to lay emphasis on the activity of the mind. His use of the term "suggestion" indicated a desire to escape from the narrower limits of association and give the mind a creative activity. Sir William Hamilton (d. 1856) also provided a new term, redintegration, which denoted the tendency of one experience to return as a whole when any part of it was given independently. But the masterpiece of the period was James Mill's Analysis of the Phenomena of the Human Mind (1829). This work was strong in its consistency and was con structed on the most uncompromising use of associationism, the doctrine which British readers accepted as being simple, practical and devoid of any tendency toward metaphysics. James Mill wavered occasionally but there were no serious lapses. The work was well done and everyone felt that the school had found its final exposition. When John Stuart Mill edited his father's work in collaboration with Bain it was already possible for him to see that the complete absence of any kind of activity was a defect which before long would make the interesting only to the historian. The French School had found the same defect in Condillac and for a time Maine de Biran's Essai sur les Fondements de la Psychologie (1822) seemed likely to initiate a new kind of activism. But the new light was extinguished in mysticism and Maine de Biran was almost forgotten until the followers of Bergson revived him as a forerunner of their master. In Germany after the decline of the idealistic philosophy there was a strong revulsion in favour of the material sciences and out of this interest grew a new crop of psychological data and theories.