A HISTORY OF SCIENCE 



it otherwise, between molecular processes and atomic 

 processes ; but the reader must be guarded against sup- 

 posing that Anaxagoras had any such thought as this 

 in mind. His ultimate mixable particles can be com- 

 pared only with the Daltonian atom, not with the mol- 

 ecule of the modern physicist, and his "infinite, self- 

 powerful, and unmixable" particles are not comparable 

 with anything but the ether of the modern physicist, 

 with which hypothetical substance they have many 

 points of resemblance. But the "infinite, self -pow- 

 erful, and unmixed" particles constituting thus an 

 ether-like plenum which permeates all material struct- 

 ures, have also, in the mind of Anaxagoras, a function 

 which carries them perhaps a stage beyond the prov- 

 ince of the modern ether. For these "infinite, self- 

 powerful, and unmixed" particles are imbued with, 

 and, indeed, themselves constitute, what Anaxagoras 

 terms nous, a word which the modern translator has 

 usually paraphrased as "mind." Neither that word 

 nor any other available one probably conveys an ac- 

 curate idea of what Anaxagoras meant to imply by the 

 word nous. For him the word meant not merely 

 "mind" in the sense of receptive and comprehending 

 intelligence, but directive and creative intelligence 

 as well. Again let Anaxagoras speak for himself: 

 "Other things include a portion of everything, but 

 nous is infinite, and self -powerful, and mixed with 

 nothing, but it exists alone, itself by itself. For if it 

 were not by itself, but were mixed with anything else, 

 it would include parts of all things, if it were mixed with 

 anything; for a portion of everything exists in every- 

 thing, as has been said by me before, and things 



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