i.l THE QUEST OF A CRITERION 57 



The principle of mechanism is that "the same causes 

 produce the same effects." This principle, of course, does 

 not always imply that the same effects must have the same 

 causes; but it does involve this consequence in the particu- 

 lar case in which the causes remain visible in the effect 

 that they produce and are indeed its constitutive elements. 

 That two walkers starting from different points and wan- 

 dering at random should finally meet, is no great wonder. 

 But that, throughout their walk, they should describe 

 two identical curves exactly superposable on each other, 

 is altogether unlikely. The improbability will be the 

 greater, the more complicated the routes; and it will 

 become impossibility, if the zigzags are infinitely com- 

 plicated. Now, what is this complexity of zigzags as 

 compared with that of an organ in which thousands of 

 different cells, each being itself a kind of organism, are 

 arranged in a definite order? 



Let us turn, then, to the other hypothesis, and see how 

 it would solve the problem. Adaptation, it says, is not 

 merely elimination of the unadapted ; it is due to the posi- 

 tive influence of outer conditions that have molded the 

 organism on their own form. This time, similarity of 

 effects will be explained by similarity of cause. We shall 

 remain, apparently, in pure mechanism. But if we look 

 closely, we shall see that the explanation is merely verbal, 

 that we are again the dupes of words, and that the trick 

 of the solution consists in taking the term "adaptation" 

 in two entirely different senses at the same time. 



If I pour into the same glass, by turns, water and wine, 

 the two liquids will take the same form, and the sameness 

 in form will be due to the sameness in adaptation of content 

 to container. Adaptation, here, really means mechanical 

 adjustment. The reason is that the form to which the 

 matter has adapted itself was there, ready-made, and 



