THE VITAL IMPETUS 153 



of these very different physical stimuli by the same 

 reaction of recognition : pleasure, dislike, avoidance, 

 greeting, or whatever it may be. To a sportsman 

 shooting wild game the stimulus may be some almost 

 imperceptible tint or shading in cover of some kind, 

 differing so little from its environment as hardly at all 

 to be seen, yet, to his experience, upon this almost 

 infinitesimal variation of stimulus depends his action 

 with all its consequences. In Driesch's example two 

 polyglot friends met and one says to the other, " My 

 brother is seriously ill," or " Mon frere est severement 

 malade," or " mein Bruder ist ernstlich erkrankt." 

 Here the physical stimulus is fundamentally different 

 in each case, but the reaction — the expressions of 

 sympathy and concern, the discussions of mutual 

 arrangements, etc., are absolutely the same. Or let the 

 one friend say to the other, " My mother is seriously 

 ill," and in spite of the very insignificant difference 

 between the consonantal sound br in this sentence and 

 the corresponding sound m in the other English sentence, 

 the reaction, that is, the subsequent conversation, and 

 the arrangements between the two friends may be 

 entirely different. 



Putting this argument in abstract form we may 

 say, generally, that two stimuli, which are, in the 

 physical sense, entirely different from each other, may 

 produce absolutely the same series of reactions ; and 

 conversely two stimuli differing from each other in 

 quite an insignificant degree may produce entirely 

 different reactions. It is also easy to see, by analysis 

 of the antecedents to the actions of the intelligent 

 animal, that these stimuli are, in the majority of cases, 

 not elemental physical agencies, but individualised 

 and integrated groupings of these agencies ; and that 

 the animal reacts, not to their mathematical sum, as 



