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THE AMEBIC AN NATURALIST [Vol. XL VI 



desirable and legitimate. Even an incomplete and inadequate 

 analogy may be very useful for descriptive purposes. But when 

 the elaboration of an analogy interferes with perception of the 

 fact it is supposed to elucidate the limitations of the method 

 become apparent. This danger may be illustrated by a recent 

 attempt to define biological evolution in physical terms. 



In the minds of most of us the term "evolution" is associated 

 probably more closely with the biological than with the physical 

 sciences. Yet the concept is essentially physical in character, 

 and is definable in exact terms probably only in the language 

 of physics. For in its last analysis we may define evolution as 

 the history of a material system undergoing irreversible trans- 

 formation. To the physicist, therefore, the study of evolution 

 is essentially the study of irreversible changes, and the law of 

 evolution is the law of increasing entropy, or, more generally, of 

 the increasing probability of the successive states of any real 

 material system. 1 



Whether such definitions have any practical advantage as aids 

 to further investigation may be questioned. Exact terms are 

 of little use in biology unless they are also concrete, that is, 

 unless they convey an idea of something that can be seen, or at 

 least imagined. Physicists are much more tolerant of mathe- 

 matical and metaphysical abstractions. The habit of using ab- 

 stract conceptions often leads to the announcement of wonderful 

 discoveries that resolve themselves, on closer inspection, into 

 purely metaphysical manipulations of terms. Thus it is con- 

 sidered one of the notable services of a "supreme biologist" that 

 he should have identified chemical reactions with organic 

 tropisms, tropicus with instincts, instincts with morals, and then 

 predicted a chemical analysis of morality. 2 



Such inferences only show that the vocabulary has been thrown 

 into solution, not that any concrete insight has been gained. 

 Physical terms can be set into formulae as mystical as a wizard's 

 incantations. Sleight of hand is discredited, but verbal miracles 

 are still performed with "scientific principles." When so- 

 called physical science runs to seed in antinomies it becomes 

 plain that we are back again in the vicious circles of meta- 

 physical deduction. 



To describe biological evolution as a process of irreversible 

 transformation seems especially inappropriate because it is of 

 ^okta, Alfred J., "Evolution in Discontinuous Systems," Journ. Wash. 

 Acad. Sciences, Vol. II, No. 1, 1912, pp. 2-4. 



»" The Chemistry of Morals," Current Literature, 52: 180, February, 

 1912. 



