i THE CHOICE OF AN EXAMPLE 65 



assume the evolutionist hypothesis. Everything is 

 marvellous, indeed, if one consider an eye like ours, in 

 which thousands of elements are coordinated in a 

 single function. But take the function at its origin, in 

 the Infusorian, where it is reduced to the mere impres 

 sionability (almost purely chemical) of a pigment-spot 

 to light : this function, possibly only an accidental 

 fact in the beginning, may have brought about a slight 

 complication of the organ, which again induced an 

 improvement of the function. It may have done this 

 either directly, through some unknown mechanism, or 

 indirectly, merely through the effect of the advantages it 

 brought to the living being and the hold it thus offered 

 to natural selection. Thus the progressive formation 

 of an eye as well contrived as ours would be explained 

 by an almost infinite number of actions and reactions 

 between the function and the organ, without the inter 

 vention of other than mechanical causes. 



The question is hard to decide, indeed, when 

 put directly between the function and the organ, as 

 is done in the doctrine of finality, as also mechanism 

 itself does. For organ and function are terms of 

 different nature, and each conditions the other so 

 closely that it is impossible to say a priori whether in 

 expressing their relation we should begin with the first, 

 as does mechanism, or with the second, as finalism 

 requires. But the discussion would take an entirely 

 different turn, we think, if we began by comparing 

 together two terms of the same nature, an organ with 

 an organ, instead of an organ with its function. In 

 this case, it would be possible to proceed little by little 

 to a solution more and more plausible, and there would 

 be the more chance of a successful issue the more 

 resolutely we assumed the evolutionist hypothesis. 



