October 21, 1898.] 



SCIENCE. 



539 



science must take into account the facts and 

 theories of psychology. The increase of 

 knowledge which has caused the creation of 

 the separate sciences is now leading to 

 further specialization, but not in the sense 

 of one science more completely ignoring the 

 others. Rather we have at present well 

 established sciences, such as astrophysics, 

 physical chemistry, biology and others 

 which take their subject-matter from two or 

 more of the older sciences. It is probable 

 that students in increasing numbers will 

 take up the inter-relations of psychology 

 with other sciences. Indeed, this tendency 

 is already well marked. Mathematics is 

 necessary as a tool for psychology, while 

 conversely several books have recently been 

 published concerned with the psychological 

 presuppositions of mathematics. The funda- 

 mental concepts of mechanics have been 

 treated as mental products by Mach, Pear- 

 son and others. At the present moment 

 the Vice-President is giving, before the Sec- 

 tion of Physics, an address on the perception 

 of light and color, while the same subject 

 was chosen by Sir George Stokes last month 

 for the subject of his address before the 

 Victoria Institute. Physics is, however, 

 leaving to psychology vision, hearing, etc., 

 though in the meantime new departments, 

 destined perhaps to become new sciences — 

 represented by the great works of von Helm- 

 holtz, Physiologische Optik and Tonempfind- 

 nngen — are being created, which draw their 

 materials in equal measure from physics, 

 from physiology and from psychology. 

 Errors of observation, the personal equation, 

 the relation between mental and physical 

 intensity, are subjects where the investiga- 

 tions of the psychological laboratory must 

 be applied in astronomy and the other 

 physical sciences. Chemistry, geology and 

 botany perhaps stand most remote from 

 psychology. Still, if physiology is in large 

 measure the chemistry of living tissues, 

 chemistry may be brought into intimate 



relations with psychology. Geology and 

 anthropology are closely related, while 

 physical geography is especially concerned 

 with the relations of man to the earth. 

 Many of the problems of evolution, so 

 essential for psychology, are best studied in 

 plants, and the applications of botany in 

 agriculture, etc., are determining factors in 

 the evolution of man. 



Physiological psychology is already ac- 

 cepted as a distinct discipline, while zoology 

 and psychology are equally intertwined. 

 It is impossible to separate physical and 

 mental evolution — witness the writings of 

 Darwin, Spencer, Huxley, Romanes, Cope, 

 Morgan and many more. Under the classi- 

 fication of this Association anthropology 

 and psychology are included in one section. 

 Several of our leading members would make 

 psychology a branch of anthropology, while 

 psychology regards ethnology and archae- 

 ology, on the one hand, and somatology, on 

 the other, as contributing much to its sub- 

 ject-matter. Sociologists find it somewhat 

 difiicult to disentangle their field from that 

 of psychology. 



If we turn to the departments of knowl- 

 edge not represented in this Association — 

 the humanities — we find psychology to be 

 a connecting link between them and the 

 physical and natural sciences. If we re- 

 gard the professions — medicine, law, the- 

 ology, teaching, journalism — we find that 

 their products when systematized into sci- 

 ences give to psychology and take from it. 

 Literature and the fine arts, both in their 

 origin and in their end, may be studied as 

 departments of psychology, though it does 

 not appear that psychology has as yet been 

 of great service to them. 



I may illustrate the inter-dependence of 

 psychology and other sciences by a definite 

 example. Much is being written just now 

 regarding the relation of consciousness to 

 the brain. The question is: Do perceptions, 

 thoughts, feelings, volitions stand in causal 



