THE ESSAYISTS 185 



of species. With faith in evolution unshaken if indeed the word 

 faith can be used in application to that which is certain we look 

 on the manner and causation of adapted differentiation as still 

 wholly mysterious." 1 The "essayists" were such men as Darwin, 

 Wallace, Huxley, Ray Lankester, and Thiselton-Dyer in England, 

 Weismann and Osborn abroad. Some of them did not them- 

 selves experiment ; but it is possible to think correctly, even about 

 experiments, without first having personally controlled the 

 breeding operations of rabbits and guinea-pigs. Moreover, the 

 quantity of data already in hand to which Darwin's work called 

 attention was so large as to occupy more than sufficiently the time 

 of the most industrious thinker who was capable of dealing with 

 complex material. The method of the essayists was not, as might 

 be gathered from the words I have quoted, to neglect experimental 

 work. Some of them constantly experimented. On the contrary, 

 their method was to use, not only the experimental, but all the 

 materials at their command, and to test their thinking in every 

 way possible. Therefore their writings necessarily took the form 

 of "essays." It is only when we use isolated fragments of evidence 

 and guess about it that we are able in biology to avoid if that be 

 a merit even the appearance of reasoning. 



307. The writings in which the Mendelian and mutation 

 hypotheses are formulated are as much essays as those which are 

 denounced as such. They are distinguished from the latter only 

 by very novel conceptions concerning the nature of science and of 

 logical proof. It would not be surprising were a section of the 

 general public, which has only the vaguest ideas as to what science 

 is and how it has been created, deluded into the belief that 

 experiment is an invariable accompaniment of special accuracy 

 in scientific observation and thought. For experiment is an 

 instrument which has been employed almost solely by men of 

 science. But that a whole school of biologists should entertain 

 that notion, apparently in complete unawareness that the question 

 as to what constitutes evidence and what proof has been elabo- 

 rately discussed by some of the greatest thinkers of the past, is 

 certainly very remarkable. It is, perhaps, conceivable that 

 experimental workers are right in neglecting patent facts and tests 

 for thinking; but I do not think I can be wrong or prejudiced 

 when I insist that so great a departure from established scientific 

 usage should be vindicated by at least some formal attempt at 

 justification. But never yet has this been done. As matters 

 1 Bateson, Darwin and Modern Science, p. 99. 



