408' 



ON ANCIENT AND MODERN SKEPTICS. 



proved that t\e senses uniformly give a true account of things, as far as 

 their respective faculties extend, still we obtain no more real knowledge 

 of matter, of the substance that is said to constitute the external world, 

 than we do of the perceptions that constitute our dreams. If, said he, 

 you affirm that matter consists of particles that are infinitely divisible, you 

 ascribe the attribute of infinity to every particle ; and hence make a finite 

 grain of sand consist of millions of infinite atoms ; and such is the train 

 of argument of the atomic philosophers. While, on the contrary, if you 

 contend, with the atomists, that matter has its ultimate atoms or primor- 

 dial particles, beyond which it is not possible to divide and subdivide it, 

 show me some of these particles, and let those senses you appeal to be- 

 come the judges. 



Such was the state of things under the Greek philosophers : the ex- 

 istence of an external world and its connexion with the mind was sup- 

 ported, and supported alone, by fine-spun hypotheses, that were perpetu- 

 ally proving their own fallacy ; and was denied or doubted of by skeptics 

 who were perpetually proving the absurdity of their own doubts. 



De^ Cartes, as we have already observed, thought, in his day, it was 

 high time to remove all doubt whatsoever, and to come to a proof upon 

 every thing ; and he zealously set to work to this effect. In the ardour 

 of his own mind he had the fullest conviction of a triumph ; and like a 

 liberal antagonist he conceded to his adversaries all they could desire. 

 He allowed a doubt upon every thing for the very purpose of removing 

 it by direct proofs, lie began, therefore, as we have already seen, by 

 doubting of his own existence : and, as we have also seen, he made sad 

 work of it in the proofs he attempted to ofCer. 



Having satisfied himself, however, upon this point, he next proceeded 

 to prove the existence of the world around him ; and, candidly following 

 up the first principle he had laid down for the regulation of his conduct, 

 he xyas determined to doubt of the evidence of the senses, excepting so 

 far as they could bring proof of their correctness. But what proof had 

 the senses to ofCev 1 The very notion of a proof, as I took leave to observe 

 in our last lecture, consists in our obtaining a fact or an idea possessing a. 

 closer agreement or connexion with the thing to be proved than the fact 

 or idea that the mind first perceives or is able to lay hold of But what 

 ideas can more closely agree or be more closely connected with an ex- 

 ternal world than the ideas produced by the senses, by which alone the 

 mind perceives such world to exist? These are ideas of identity, of self- 

 agreement ; and consequently ideas, which, like that of consciousness, it 

 is neither possible to doubt of or to prove. They form, for the most part, 

 a branch of intuitive knowledge, and we are compelled to believe whether 

 we will or not. 



I say for the most part^ for I am now speaking of the common eflfect 

 of external objects upon the senses, and upon the mental organ. I am 

 ready to admit that, under particular circumstances, the ideas they excite 

 may not be perfectly clear ; we may be at too great a distance from the 

 object, or the sense of sight, smell, taste, or touch, may be morbidly or 

 accidentally obtuse ; but in all these cases a sound mind is just as conscious 

 of having ideas that are not clear, as it is, under other circumstances, of 

 having distinct ideas. There is no imposition whatever : the mind equally 

 knows that it has certain knowledge in the latter instance, and that it has 

 uncertain knowledge in the former. I mean if it will exert itself to know 

 !>v the exercise^of its own activity ; for otherwise it may as well mistake in- 



