52 BULLETIN OF THE 



Nay, further than this, in the inevitable reaction thaf is beginning 

 to make itself felt against the avowed revival of the materialism 

 of Epicurus and Lucretius — for we all know now that the chemico- 

 physical hypothesis of life is not a new induction of modern science, 

 but an ancient Greek speculation reappearing in modern petti- 

 coats — that other Greek speculation of the threefold Psyche, the 

 doctrine taught by Plato and Aristotle, and which Galen accepted 

 on their authority, the doctrine of a vegetable, an animal, and a 

 rational soul, a human trinity coexisting in every human being, is 

 once more rehabilitated and finding followers — likely, indeed, as I 

 think, to obtain more followers than perhaps any of you yet suppose. 

 And these followers are by no means confined to metaphysicians or 

 churchmen, they can be found also already among the biologists. 

 It is an English biologist of good repute, and of no mean abilities, 

 who takes occasion, in a technical biological work published this 

 very year, to express his belief that the Greek conception of the 

 threefold Psyche "appears to be justified by the light of the science 

 of our own day." 3 



For myself I must confess at once that I am quite unable to join 

 either of these opposing camps as a partizau. I cannot accept the 

 more strictly vitalistic views, because I am compelled continually 

 to recognize the operation of purely chemical and physical forces 

 in living beings. On the other hand, there are whole groups of 

 phenomena characteristic of living beings, and peculiar to them, 

 for which the chemico-physical hypothesis offers no intelligible 

 explanation. 



From this point of view the various processes and functions of 

 living beings may indeed be divided into two classes, of which the 

 first may be regarded with more or less certainty as the special re- 

 sults, under special conditions, of the very same forces that operate 

 in the inorganic world ; while the second, to which alone I would 

 apply the term vital, are not merely in every respect peculiar to 

 living beings, and hitherto utterly inexplicable by the laws of 

 chemistry and physics, but are so different in character from the 

 phenomena of the inorganic world that it does not seem rational to 

 attempt to explain them by these laws. 



Let me refer briefly to the processes and functions belonging to 

 the first class. Here I place all those more strictly chemical 

 processes by which, within the very substance of vegetable pro- 

 toplasm, inorganic elements are combined into organic matter, 



