206 BIOLOGICAL LECTURES. 



As William Whewell has well said in one of his " aphorisms 

 concerning science," - 



" The distinction of Fact and Theory is only relative. Events 

 and phenomena, considered as particulars which may be colli- 

 gated by Induction, are Facts; considered as generalities 

 already obtained by colligation of other Facts, they are Theo- 

 ries. The same event or phenomenon is a Fact or a Theory, 

 according as it is considered as standing on one side or the 

 other of the Inductive Bracket." l 



The truth of this aphorism is quite as pertinent to-day as 

 when it was written in 1840. The notion that what is visible 

 is "fact," and that what lies beyond vision is "theory," has 

 not been fully outgrown even among men of science. Those 

 who presume to act as Levites in charge of the ark of "fact," 

 should beware of blundering into a distinction that places most 

 of our knowledge to the credit of " theory." There is, indeed, 

 " a mask of theory over the whole face of nature, if it be theory 

 to infer more than we see" (Whewell.) 



The claim has been made that epigenesis stands for "fact " 

 and evolution for "theory." One author, with Wolff's " Theory 

 of Generation " on his lips, affirms that "epigenesis is a state- 

 ment of morphological ( ! ) fact ; it is not, and does not pretend 

 to be, an explanation of those facts!' 2 What would the earlier 

 prophets of epigenesis have exclaimed at such apostasy ? No 

 "theory" in the irepl ^UHDV yevecrea)<; ? None in the " Exerci- 

 tationes de Generatione Animalium" or the " Additamenta " ? 

 None in the " Theoria Generationis " ? Would it not be a little 

 nearer the "fact " to say that Bonnet and Haller did not pre- 

 tend to explain generation ? Was not Wolff quite right when 

 he complained, 



" Qui igitur systemata praedelineationis tradtint, generationcm 

 non explicant, sed, earn non dari, affirmant" '? Was there no 

 "pretension" in the "vis corporis essentialis" of Wolff? in 

 the "vis productrix" of Needham ? in the " impressio idealis" 

 of Harvey? or in the " -fyvyiK'n />%??" f Aristotle? Who 

 were the authors of those "mechanical explanations" of de- 



1 Phil. Ind. Sc., p. xli. 



2 G. C. Bourne, Science Progress, April, 1894, p. 108-109. 



