SYSTEMATIC PSYCHOLOGY--J. S. MILL., BAIN, LOTZE
TURNING now definitely to the first of our three periods, we find that "pure" psychology during this period is dominated by a few principal figures, notably J. S. Mill, Bain and Lotze. If we were to insist on a strictly chronological account, we should have to include Herbert Spencer also; for the first edition of his Principles of Psychology appeared in 1855. But in spirit he belongs distinctly to our second period, for his whole outlook is in its very essence evolutionary, and indeed he became an influential figure in psychology only after the publication of the second and revised edition of his Principles (now incorporated as an integral part of his Synthetic Philosophy) in the early seventies. John Stuart Mill's work also falls partly in our first and partly in our second period, his chief contributions to psychology being found in his Logic, published in 1843 and in the Examination of Sir William Hamilton's Philosophy published in 1865. In spirit, however, he belongs to the first period rather than the second. His most influential addition to psychological theory was, moreover, beyond all doubt, his doctrine of "mental chemistry" enunciated in the earlier work.
In conformity with his freer, tenderer and less pedantic nature, he set about, in this; doctrine, to diminish the rigours of the uncompromising associationism of his father. For the rigid mechanical scheme of interaction between unitary ideas, in terms of which James Mill had described the working of the mind, J. S. Mill substituted a "chemical" conception, according to which complex thoughts and feelings were indeed generated by, but not in all cases merely com-