THE DISCOVERY AND TESTING 45 



as to whether unhealthy conditions are causes of racial degenera- 

 tion or of evolution, no' suitable or practicable experiment can be 

 thought of. 1 Hundreds or thousands of experiments have been 

 performed, it is true, but with the most inconclusive results. 2 Here, 

 before we are able to reach a valid conclusion, we must appeal to 

 a far wider area of reality, which includes not only the experimental 

 data, but very much more besides. 3 



75. In biology, then, the essence of the experimental method 

 does not consist " in requiring every suggestion (or hypothesis) to be 

 put to the test of experiment before it is admitted to the scientific 

 status " an impossible task in many cases and foolish in more ; 

 but only in requiring that every suggestion which can usefully be 

 so tested shall be so tested. Since such suggestions are relatively 

 very few, exclusive reliance on experiment would result in a 

 classification of facts so imperfect as to be unworthy of the name 

 of science. The statement, " No doubt nature has carried out 

 prodigious experiments ; but we can never be certain that we know 

 how she has obtained her results until we can repeat the process 

 for ourselves," 4 implies a lack of insight or a singular unawareness 

 of known facts. For example, every instance of an individual 

 who has offspring during or after suffering from a general disease 

 is a very stringent experiment carried out by nature and not to be 

 bettered by man. The accumulated result of millions or billions of 

 such experiments, continued for thousands of years on hundreds of 

 successive generations, are because the instances are so numerous, 

 obvious, and confirmatory of one another, because we are able 

 successfully to employ every known method of induction, and 

 because we can test the thinking thoroughly by deduction every 

 whit as easy to infer with certainity as if they had been undertaken 

 by the most careful experimental worker. 5 " Controversy " 6 implies 

 criticism. To abandon it would be to abandon the critical method, 

 which, in turn, would mean the rash and unquestioning acceptance 

 or ignoring of hypotheses. Biological disputes are comparatively 

 seldom due to disagreements about facts. Almost always the 

 opponents of a hypothesis suppose that its authors have drawn 

 wrong inferences, and their objections are attempts to test the 

 latter by demonstrating that they are not in harmony with the 

 conceived system of reality. Fortunately, however, the labours 

 of experimental workers have tended, on the whole, to increase, 

 rather than diminish, controversy. The experimental method is 



1 See 135. 2 See 132-4, 140-4, 160. 3 See 145 et seq. 



4See S3 (footnote). 5 See chapter xiii. 6 See 53 (footnote). 



