i THE QUEST OF A CRITERION 57 



of individuals, on divergent lines, each ending at a 

 crossing from which new paths radiate, and so on 

 indefinitely. If our hypothesis is justified, if the 

 essential causes working along these diverse roads are 

 of psychological nature, they must keep something in 

 common in spite of the divergence of their effects, as 

 school-fellows long separated keep the same memories 

 of boyhood. Roads may fork or by-ways be opened 

 along which dissociated elements may evolve in an inde 

 pendent manner, but nevertheless it is in virtue of the 

 primitive impetus of the whole that the movement of 

 the parts continues. Something of the whole, therefore, 

 must abide in the parts ; and this common element 

 will be evident to us in some way, perhaps by the 

 presence of identical organs in very different organisms. 

 Suppose, for an instant, that the mechanistic explana 

 tion is the true one : evolution must then have occurred 

 through a series of accidents added to one another, 

 each new accident being preserved by selection if it 

 is advantageous to that sum of former advantageous 

 accidents which the present form of the living being 

 represents. What likelihood is there that, by two 

 entirely different series of accidents being added to 

 gether, two entirely different evolutions will arrive at 

 similar results ? The more two lines of evolution 

 diverge, the less probability is there that accidental outer 

 influences or accidental inner variations bring about the 

 construction of the same apparatus upon them, especially 

 if there was no trace of this apparatus at the moment 

 of divergence. But such similarity of the two products 

 would be natural, on the contrary, on a hypothesis like 

 ours : even in the latest channel there would be some 

 thing of the impulsion received at the source. Pure 

 mechanism, then, would be refutable, and finality , in 



