130 THE FOUNDATIONS OF ZOOLOGY 



bodies, on a cold day, or under similar circumstances. As, in 

 this case, our experience is pretty extensive, the deduction is safe 

 and reasonable ; but when a young man who had passed his life 

 in the tropics spent the night on top of a high mountain with 

 my students, he was so far from deducing anything from the 

 frosty morning air that he was, at first, alarmed by the behavior 

 of the vapor of his breath. 



If Huxley is right, if the logical basis for confidence in 

 nature is evidence, it seems clear that no amount of knowledge 

 can ever give it any other basis ; for nothing seems more obvious, 

 or more strictly logical, than our inability to deduce anything 

 from a single experience. The burnt child may dread the fire as 

 much as if it had been burned twenty times, but the only way 

 for it to learn whether, and to what degree, its dread is wise 

 and prudent, without passing through the slow and painful pro- 

 cess of selection, is to get knowledge, for a single experience 

 affords no basis for any logical process. 



While the emotional value of a sensation is, no doubt, limited 

 by inherited structure, and dependent, to some degree, on inten- 

 sity, its objective value as knowledge is regulated in accordance 

 with the statistical law of probability. 



If the history of what we call our universe were complete 

 from beginning to end ; if everything which exists in it were 

 reduced to mechanical principles, and traced back to primitive 

 nebulosity, this history would be only a single experience in cos- 

 mogony, so far as the history of universes is in question. If we 

 were to find, somewhere, a second nebulosity, we would not be 

 able to infer anything, except from the worthless analogy of a 

 single experience ; nor would we be able to infer or deduce, from 

 our own, anything, not already known, with more than reasonable 

 confidence. If we were still ignorant of any part of our order of 

 nature, we should have no way to find out but the way we have 

 now ; and while our confidence in its stability would be reasonable 

 and judicious, it would not be necessary or absolute unless our experi- 

 mental knowledge were also absolute. 



It seems to me that the truth for which Huxley strives, and 

 hits with imperfect aim, would be more correctly expressed by the 

 statement that, if our knowledge of nature were to be made com- 



