ON THE NATURE OF LIFE 193 



non-energetic agency, and therefore something that was quite 

 outside the scope of physical investigation. This was Cartesian 

 vitalism, an attitude that persisted throughout the greater part 

 of the eighteenth century. 



But with the development of modern chemistry and physics 

 biology again applied itself to the investigation of modes of 

 functioning, and, with every new advance made by physical 

 science, our knowledge of the ways in which the animal body 

 worked became more and more intimate. Now it will be clear 

 to the reader, from what we have said in Chapter IX., that all 

 that has been attained by the application of physical and chemical 

 methods has been a great refinement of our analysis of organic 

 activities, and not at all an explanation of animal behaviour. 

 Just the same things may be said about hypotheses of develop- 

 ment and evolution. The best known of such- — Weismann's 

 theory of the germ plasm — might have become a physico- 

 chemical one, but there is every indication that it has now quite 

 broken down, so that, as yet, we have no explanation of heredity, 

 which involves only the concepts of physics and chemistry. We 

 have, it is true, an analysis which is, gradually becoming more 

 'minute, but a little reflection will conviace the reader that this 

 also is not an explanation. 



Within the last generation there has been a recrudescence of 

 vitalism — " neo-vitalism " it is now called, being obviously some- 

 thing that seems to be different from the Cartesian speculations 

 about the sensitive soul. At its best this is seen in the " psy- 

 choids " and " entelechies " of Driesch and others, concepts 

 which are applicable to living things only, and not to chemical 

 and physical phenomena. At its worst modern vitalism is 

 exhibited in the crude and even grotesque " spiritualism " which 

 has attained such a vogue with the less resolute thinkers of our 

 own generation. This, then, is the modern impasse to which 

 biology has come. Purely physico-chemical explanations of life 

 are not satisfactory, and the immaterial and non-energetic 

 agencies that are being invoked in their place can have no interest 

 for science, since they cannot be the objects of investigation. 



Now it may help the reader in trying to apprehend this situa- 

 tion if he notes that physical science itself is apparently con- 

 fronted with a somewhat similar impasse. Trace the history of 

 physics during the last two centuries, and it will be seen that its 

 face is being changed all the while. There was the " classical " 



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