THE SPECTRE OF VITALISM 443 



The first proof is introduced by a long account of the facts 

 of morphogenesis or the development of the individual organism. 

 Driesch commences with the fact that, if we go back early enough 

 in the history of an embryo, we reach a time when all its parts 

 are equally capable of giving rise to an adult organism : when, in 

 fact, there has been no differentiation of parts and each portion 

 of the embryo is as capable as any other portion of developing 

 into any of the specialised structures of an adult organism. 

 Any portion of an embryo which answers to this definition is 

 called by Driesch an equipotential system. If each embryonic 

 part be equally capable of developing into any of the varied adult 

 parts, what factors are they which control the development into 

 a harmonious whole ? Driesch shows, in the first place, that 

 the absolute size of the system and the relative position of any 

 point in it are factors in accounting for the trend of develop- 

 ment. But he points out that they cannot alone explain de- 

 velopment : there remains the "prospective potency" of the 

 system — that is to say, its power of developing in certain 

 directions which terminate in the structure of an adult organism. 

 What is this potency ? Let us refer to it as E. Driesch then 

 considers every possibility that can be named as to the nature 

 of E. From the mechanistic point of view there are, he says, 

 three possibilities. There is, firstly, the possibility that " for- 

 mative stimuli " are sufficient to account for development ; there 

 is, secondly, the possibility of a chemical basis ; and there is, 

 thirdly, the possibility "of a real machine in the system," one 

 more or less resembling that suggested by Weismann. Driesch 

 takes two pages to refute the first possibility, four pages to refute 

 the second possibility and four pages to refute the third ; and the 

 very next page is headed by the legend, "Vitalism Proved." 1 

 This startling announcement is founded on the following logical 

 process : There are four possibilities as to the nature of E ; it 

 may be either any one of the three already named or it may 

 be "a true element of nature." But it has been proved that it 

 is none of the three first named ; therefore it must be the fourth. 

 Henceforward it figures under the title of " entelechy." 



I am aware that, in pausing to point out the sundry fallacies 

 involved in the above argument, I shall be casting reflections 

 on my reader's perspicacity. Nevertheless, since Driesch ap- 



1 The actual legend is " The autonomy of morphogenesis proved " : but 

 Driesch defines "autonomy of morphogenesis" as synonymous with "vitalism." 



