The Imperfections of Man 



Evolution is one of the subjects upon which laymen have long 

 felt themselves entitled to express an opinion; formerly, the 

 opinion that evolution does not occur; latterly, that it does not 

 occur in the way that biologists now suppose. The chief among 

 several causes of their present discontent is approximately as 

 j follows. Biologists believe that evolution has come about 

 1 through the action of material forces, in the sense that it does 

 not unfold itself according to a preordained purpose or super- 

 imposed design. To laymen, an argument which takes no 

 account of design or purpose or Aristotelian Final Causes is 

 utterly unsatisfying and implausible. How can mere unguided 

 material forces be responsible for the miraculous optical engin- 

 eering of the eye; for the exquisite functional aptitude of a bird''s 

 wings; for the almost finicky precision of mimicry? Is it not go- 

 ing a little too far to impute these splendid accomplishments 

 to what Bacon called the ^'casual felicity of particular events?' 

 These are intelligible complaints, but they are founded upon 

 a misconception, namely, that evolution is a perfectionist 

 process. The eye, for example, is beset by chromatic and 

 spherical aberration, and is not correctly centred along its 

 optical axis; Helmholtz, the grand master of physiological 

 optics, said that an optician would be ashamed to make an 

 instrument with such elementary physical faults.* Many of the 



* [Vortrdge und Reden, I, p. 286, 1908. Helmholtz had obviously been 

 exasperated by contemporary 'nature-philosophers' of the perfectionist 

 school: see his Treatise on Physiological Optics, American edition, I, p. 185.] 



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