22 THE THEORY OF [pt. 



published his results in a valuable series of papers from 1911 to 191 8. 

 He concluded that the pursuance of laboratory work demands as its 

 minimum of system what he called "Radical Experimental Deter- 

 minism", and that there was difference of opinion as to whether 

 this might regard conscious or unconscious mental processes as links 

 in the chain of determinate causation. On this point Jennings and 

 Loeb were antagonists, but both were united against Driesch, from 

 whose writings it now appeared that psychical events might or might 

 not affect physical events according to circumstances, and that the 

 entelechy was subject to no general laws. Neal had maintained that 

 the experimentally discoverable perceptual determiners in living 

 things were insufficient to account for the effects produced in them. 

 Jennings pointed out that, if this meant that the non-perceptual 

 (mental) determiners acted supplementarily to the others and not 

 instead of them, it was compatible with radical experimental deter- 

 minism. But, if it was said that some of the determiners were non- 

 perceptual and could not be known at all, then it was incompatible. 

 Now it was just this that Driesch had been saying. "A complete 

 knowledge", he wrote, "of all physico-chemical things and relations 

 (including possible relations) of a given system at a time t would 

 not give a complete characterisation of that system if it is a living 

 system. . . . Practically we may say that complete knowledge of the 

 physico-chemical constitution of a given egg in a given state and of 

 the behaviour following this constitution in one case, implies the 

 same knowledge for other cases (in the same species) with great 

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

 more. It would not even be a probability if we did not know the 

 origin of a given egg in a given state, i.e. that the egg was the tgg, 

 say, of an ascidian. But to know this history or origin, is of course, 

 already more than simply to know its physico-chemical constitution 

 and its consequences in one case, which suffices in the realm of the 

 inorganic. It may be that the eggs of echinoidea, fishes, and birds, 

 are the same in all the essentials of physico-chemical constitution. 

 Something very different happens in each case on account of the 

 different entelechies. In spite of this we know with great probability 

 what will happen from one case if we know that this egg comes 

 from a bird and that from an echinoid. Therefore, practically, ex- 

 perimental indeterminism is not a great danger for science." 



But the matter was taken up by various writers, and Lovejoy, 



