THE DEVELOPMENT OF PSYCHOLOGY. 297 



criminated by Descartes and Hobbes. The same conception (motion) 

 is used to explain the feelings, which, when pleasurable, are the result 

 of the vital motion being '* helped " by the motions which, having 

 produced conceptions in the head, afterward proceed to the heart.' 

 But external objects not only " cause conceptions, and conceptions 

 ajopetite, and fear ; " as the latter are " the first unperceived beginnings 

 of our actions," and as in a state of doubt, appetite and fear rapidly suc- 

 ceed one another, " this alternate succession of appetite and fear .... 

 is that we call deliberation." ^ As all Hobbes's successors of the same 

 school have followed him in thus ignoring the ego, it may be inferred 

 that every system of experimental psychology is self-condemned 

 to incompleteness, and that no system can cover the whole of the 

 ground which does not make what can only be called metaphysical 

 assumplTions. 



The psychological advances made by Hobbes were then — that he 

 helped to banish the imaginary entities of the Schoolmen, and substi- 

 tuted for them hypotheses that implied at least verce causm (true 

 causes) ; that he replaced the method of deduction from assumed prin- 

 ciples by that of observation (which was not yet, however, that of 

 introspection), and thus founded the inductive philosophy of the mind ; 

 and that by his summary rejection of the common metaphysical as- 

 sumptions, and his patient building up on an independent foundation, 

 he decisively separated psychology from the metaphysics in which it 

 was enmeshed. 



If the psychology of Hobbes bears evident marks of the daring, 

 speculative character of contemporary physical science, that of Locke 

 witnesses to the change in the tone and spirit of inquiry. If the key- 

 word tg Hobbes is Galileo, that to Locke is Sydenham. Locke and 

 Sydenham were both surgeons, were friends, and were of kindred 

 cautious temperament; and the pacific revolution which Sydenham 

 wrought in medicine has been described in language that, with the 

 necessary change of terms, might word for word be applied to the 

 great psychological advance initiated by Locke. A competent writer 

 describes Sydenham as being — 



"most careful to exclude the prevailing theories from affecting his study of the 

 facts of disease: he followed the inductive method which his countryman, Ba- 

 con, had just completed, and under the guidance of his friend John Locke, 

 himself a surgeon, he applied it to the investigation of disease with splendid 

 success. The laws ruling the prevalence of epidemics were elucidated, and new 

 and old diseases described with an accuracy and graphic coloring which have 

 ever since remained unrivaled. The treatment of disease Sydenham found 

 lamentably uncertain from want of any fixed principle, and from the countless 

 remedies prescribed mainly in accordance with a capricious fashion. In place 

 of this, he left therapeutics an art ordered by the principle of aiding ISTature, 

 and observing the indications afforded by morbid processes themselves. . . . 



1 "Human Xature," p. 31. 2 ibj^j., pp. 67, 68. 



