4 i6 SCIENCE PROGRESS 



not such a belief involve fatalism, and is it not destructive of 

 all theories of moral responsibility ? And how can the con- 

 ception of " purpose " arise out of the blind interaction of 

 physical forces? Notwithstanding these truly formidable diffi- 

 culties, philosophers and men of science boldly affirmed that 

 all manifestations of life were subject to the same uniformities 

 and inevitable sequences, which had received the name of 

 natural laws. They asserted that all conduct or acts are the 

 necessary outcome of our material organisation, and that they 

 are not in the smallest degree affected by mind or any similar 

 entity, in so far as any such entity is a separate thing from our 

 bodily functions. Thus there arose two schools of thinkers, 

 one of whom affirmed that all the manifestations of life are 

 physico-chemical in character, while the other alleged that a 

 mental or spiritual force acts in co-operation with the material 

 forces known to science, which forces alone are inadequate to 

 furnish an explanation of the observed phenomena. The latter 

 school are now commonly known as vitalists, while the former 

 have often been described as mechanists. 



It is evident that this controversy is no other than the ancient 

 problem of free-will and determinism. Determinism was 

 asserted by the ancient Greeks in the philosophy of Democritus. 

 It was powerfully supported by Lucretius. It died out during 

 the darkness of the Middle Ages, to revive with vigour at the 

 time of the Renaissance. Descartes applied the most rigid 

 determinism to the activities of all animals save man, who was 

 not then regarded as an animal. In the succeeding century 

 La Mettrie in L'homme machine included man within a 

 revised Cartesian theory. But in the main the defence of deter- 

 minism has fallen upon Scotch and English philosophers, and 

 the so-called materialistview has remained specially characteristic 

 of the thinkers of our own country. 



The whole subject has now been carried to a far higher level 

 of discussion by the advance of physiology, and the question 

 has become definitely a physiological problem. It is obvious 

 indeed that the agencies at work in human activity can only be 

 properly investigated by the science which deals with the nature 

 of organic functions. If we want to know by what process a 

 man performs a certain act, the proper scientific method is to 

 look inside him and see ; that is, to carry out an experiment 

 upon him or upon some other animal which may furnish us by 



