INTRODUCTION. XV 



observation what was in reality a mere supposition.^ Nor does it imply 



any great credulity on the part of Aristotle, that he should unhesitatingly 



have accepted such a report. For it is not the actual falseness of a 



statement, but its inconsistency with our previous experience, which 



makes the ready acceptance of it to be an act of credulity. A modern 



naturalist knows from an examination of a vast number of species that, 



as a rule to which there is scarcely an exception, the mammalian neck 



contains seven vertebrae, and that in no known instance are there less 



than six. Possessing this knowledge, he would show great credulity 



were he to accept without further question any account of a mammal 



with but one cervical bone. But to Aristotle, who had not this previous \ 



k nowled ge, there would seem nothing strange in such an account ; arid 



as there was nothing in it to rouse his suspicions, he would accept it 



without question. In no instance do we find similar outrageous errors, 



when Aristotle, as he often does, states a fact to have been derived from 



his own observation. So far, indeed, as I can judge, he seems to have] 



been anything rather than a careless and inaccurate observer. It cannot, 



of course, be maintained that he was able to observe with the precision 



of a modern man of science. His substratum was insufiicient for this. 



To observe, unless the phenomena be of the very simplest, it is not 



enough to keep the eyes open and to watch with honest intention for 



what may turn up. To be effectual, observation requires a stock of previou s | ^fe— ** 



knowledge. He that has most of this will see best and most. Tell 



me, said even the long-experienced Faraday, when asked to be witness 



of an intended experiment, tell me what you expect me to see, that I 



may be able to see it. 



A second source of Aristotle's failure is found in his habit of has^ty yenf^- l.^ 

 ralisatinn,- That he was constantly generalising on a very scanty basis of 

 facts cannot be denied. The stage to^vhich biology had then attained 

 made this a matter of necessity. ThejArst stage in every new science 

 is the simple accumulation ofjjacts. The next, if it may be called next, 

 LVseeing that it must go hand in h and witji the first, is the rough sorting 

 of these facts and the reduction of their chaos to some kind of order. 

 This is effected by tQmgorary generalisations, which, though they may 

 be very far from the ultimate truth, yet serve for the time the necessary 

 purpose of enabling the observer to manage his otherwise unwieldy 

 material. All that can fairly be demanded at this period is that there 

 shall be diligence in the collection of facts, and that the temporary 

 generalisations shall not be obviously untrue. As regards Aristotle's 



' Possibly, however, not a mere supposition, but a hasty generalisation from some single 

 example, in which the cervical vertebrae had been affected as they are occasionally in the 

 hyaena, and become anchylosed. And this is the more possible, inasmuch as the anchy- 

 losis has actually given rise to a similar belief concerning the hyaena, namely, that it has 

 but one bone in the neck. Cf. Regne Animal, i. i6o. 



a 



