CIRCULATION OF THE BLOOD. 131 



Charybdis, and then hiss and foam, and are tossed hither and 

 thither; so do they who reason against the evidence of their 

 senses. 



Were nothing to be acknowledged by the senses without 

 evidence derived from reason, or occasionally even contrary to 

 the previously received conclusions of reason, there would now be 

 no problem left for discussion. Had we not our most perfect 

 assurances by the senses, and were not their perceptions con- 

 firmed by reasoning, in the same way as geometricians proceed 

 with their figures, we should admit no science of any kind; for 

 it is the business of geometry, from things sensible, to make 

 rational demonstration of things that are not sensible; to ren- 

 der credible or certain things abstruse and beyond sense from 

 things more manifest and better known. Aristotle counsels 

 us better when, in treating of the generation of bees, he says: 1 

 "Faith is to be given to reason, if the matters demonstrated 

 agree with those that are perceived by the senses; when the 

 things have been thoroughly scrutinized, then are the senses 

 to be trusted rather than the reason." "Whence it is our duty 

 to approve or disapprove, to receive or reject everything only 

 after the most careful examination; but to examine, to test 

 whether anything have been well or ill advanced, to ascertain 

 whether some falsehood does not lurk under a proposition, it 

 is imperative on us to bring it to the proof of sense, and to 

 admit or reject it on the decision of sense. Whence Plato in 

 his Critias, says, that the explanation of those things is not 

 difficult of which we can have experience; whilst they are not 

 of apt scientific apprehension who have no experience. 



How difficult is it to teach those who have no experience, the 

 things of which they have not any knowledge by their senses ! 

 And how useless and intractable, and unimpregnable to true 

 science are such auditors! They show the judgment of the 

 blind in regard to colours, of the deaf in reference to concords. 

 Who ever pretended to teach the ebb and flow of the tide, or 

 from a diagram to demonstrate the measurements of the angles 

 and the proportions of the sides of a triangle to a blind man, 

 or to one who had never seen the sea nor a diagram? He 

 who is not conversant with anatomy, inasmuch as he forms no 



1 De Generat. Animal, lib. iii, cap. x. 



