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description of the facts of evolution. Numerous attempts have 

 been made to define the relations of selection and evolution by 

 means of Aristotle's categories of causation. Perhaps the best 

 example of this is by Professor Cattell : 



" In discussions on the theory of evolution we find Neo-Dar- 

 winians saying that ' natural selection ' is the cause of the origin 

 of species, and Neo-Lamarckians saying that the environment 

 and the movements of the animal are the causes of adaptations. 

 Now in these cases the word ' cause ' is used ambiguously, igno- 

 rance of the facts of evolution being concealed by the exhibition 

 of ignorance of logic. 



" I wonder how many men of science have read Aristotle, or 

 understand his distinctions between material, efficient, formal 

 and final causes. We are not here concerned with a formal 

 cause, the idea or plan of a thing, nor with a final cause, the 

 end for which it is made ; but no student of organic evolution 

 can afford to ignore the distinction between material and efficient 

 causes, or between the occasion and the efficient cause of an 

 event. The material cause is that of which a thing is made, 

 one of the occasions or necessary conditions of its existence ; 

 the efficient cause is that which produces a thing and makes it 

 what it is. When no qualification is used cause should mean 

 efficient cause or vera causa. 



" ' Natural selection ' is no cause of the origin of species, but 

 may be the cause of the annihilation of unfit species. Whether 

 or not the environment, or consciousness, or the movements of 

 animals are causes of hereditary modifications are open ques- 

 tions. What is called the cause of an adaptation is, however, 

 usually only its occasion." 1 



Selection is neither a formal, a final, a material nor an effi- 

 cient cause of evolution. Evolution goes on without selection. 

 This shows how poorly adapted the Aristotelian categories are 

 for the expression of relations so complex as those of evolution. 

 Those who depend upon systems of abstract formulation for the 

 comprehension of biology can fit selection and evolution into 

 these categories only by saying that evolution is the cause of 



'Cattell, J. McKeen, 1S96. The Material and Efficient Causes of Evolution. 

 Science, N. S., 3 : 66S. 



