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THE AMEBIC AN NATURALIST [Vol. LI 



evolution theory in the late nineties, from which it was 

 rescued only by the active movement towards an ob- 

 jective, experimental accumulation of facts about the sub- 

 ject. But the danger which lurks in formal logic is always 

 threatening the progress of science. In the field of sci- 

 ence in which we are interested the most recent conspicu- 

 ous example of it is found in the vicious attacks on Men- 

 delism, which upon analysis can be seen to have their only 

 basis in a formally logical, so-called "proof" that it can 

 not be true. The danger is so insidious, and takes such 

 diverse forms, that one feels justified in quoting a brief 

 statement made by Professor F. C. S. Schiller,^ which 

 might well, in sufficiently large type, be hung upon the 

 wall of every biological laboratory, as a constant reminder 

 that the foundations of scientific truth lie in experiment 

 and observation, not in logic. Schiller says : 



The proof that any logic, which declines to consider the question of 

 the real truth of the reasonings it attempts to deal with, necessarily 

 condemns itself to utter formality is easily given, and very instructive. 

 It is a formal characteristic of every assertion that it claims truth, ab- 

 solutely and without reservation or suggestion of fallibility. Hence it 

 follows both if (a) the question of the actual value of this claim is ruled 

 out of order, and if (b) the assertion is accepted at its own estimation, 

 that the distinction between true and false must, in fact though not in 

 name, disappear from Logic. For all assertions will be held true be- 

 cause they formally claim truth ; because none profess to be false, error 

 no longer exists — for Logic. Thus the logical form of an assertion 

 affords no means of deciding upon the real value of its claim to truth, 

 and hence any logic which restricts itself to the study of this form 

 inevitably accepts a truth-claim as the equivalent of real truth. It is 

 like a bank which does not distinguish between promises to pay and hard 

 cash. 



Then clearly the question to which we want an answer 

 is not whether natural selection cmi cause evolutionary 

 changes, but rather whether it does cause such changes 

 in any significant degree or extent. In other words, we 

 shall prefer the ''hard cash" of objective experimental 

 evidence to any logical ''promise to pay," however tight 

 and compulsive its reasoning. 



4 Schiller, F. C. S., "Formal Logic. A Scientific and Social Problem. "J 



