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THE AMERICAN NATURALIST [Vol. XLYII 



judgment of the validity of this sort of vitalism. Now, 

 it appears to me that in his recent attempt to show that 

 such vitalism does not seriously affect experimental 

 science — in the letter quoted by Lovejoy — Driesch in ef- 

 fect admits this; pulls the empirical foundations from 

 beneath his theory, so far as they depend on the occur- 

 rence of any particular cases in which two perceptually 

 similar systems behave differently, and is left in the posi- 

 tion of maintaining in general what he denies for all 

 particular cases; at least he saves himself from this 

 position only by the expedient of asserting the ' 1 very 

 great probability" of certain conclusions, in place of 

 their certainty. The passage lends itself so fully to the 

 arguments of those convinced that any doctrine involv- 

 ing experimental indeterminism has no sound basis that 

 I should have hesitated to make use of it until similar 

 statements were incorporated into some formal publica- 

 tion by Driesch, save for the fact that, with Driesch 's 

 permission, it has already been given currency by Love- 

 joy. 37 The passage is as follows: 



Practically, we may say that complete knowledge of the physico- 

 chemical constitution of a given egg in a given state and of the behavior 

 following this constitution in one case implies the same knowledge for 

 other cases (among the same species) with a very great probability. 

 But this is a probability in principle and can never be more. It would 

 not even be a probability in the case that we did not know the origin 

 (or history) of the "given egg in a given state," viz.: that this egg is 

 the egg, say, of an ascidian. But to know this " history " or " origin " 

 is, of course, already more than simply to know " the physico-chemical 



It may be that the eggs of fishes, echinoids and birds are the same in 

 all essentials of the physico-chemical constitution. There happens 

 something very different in the different eases on account of the different 



In spite of this; we know what will happen with great probability 



account here the existing differences in size, shape, etc., of the eggs in 

 question; these may be not among the "essentials.") 



"Science, November 15, 3912. (See note at end of the present paper.) 



