390 



ON HUMAN UNDERSTANDING. 



as ^himself <although not to the same ej^tent or demonstration; and for 

 this obvious reason, because they have not equally doubted and examined. 



It is difficult to be grave on such a subject. What would be thought 

 or said of any individual in the present audience who should rise up, and 

 openly tell us that he had been long troubled with doubts whether he really 

 existed or not ; that his friends had told him he did, and he was inchned 

 to believe so ; but that as this belief might be a mere prejudice, he was at 

 length determined to try the fact by asking himself this plain question, — 

 *^ Do I think ?" Is there a person befoi-e me but would exclaim, almost 

 instinctively, Ah ! poor creature, he had better ask himself another plain 

 question, — whether he is in his sober senses ?" 



If, however, we attempt to examine seriously the mode which M. Des 

 Cartes |hus proposes of following up'his own principles, it is impossible 

 not to be astonished at his departure from them at the first outset. Instead 

 of doubting of every thing and proving every thing, the very first position 

 before him he takes for granted : " I think ; therefore I am." Of these 

 two positions, he makes the first the proof of the second, but what is the 

 proof of the first ? If it be necessary to prove that he is, the very ground- 

 work of his system renders it equally necessary to prove that he thinks. 

 But this he does not attempt to do : in direct contradiction to his funda- 

 mental principles he here commits a pctitio principii^ and takes it for 

 granted. I do not find fault with him for taking it for granted ; but then 

 he might as well have saved himself the trouble of manufacturing an im- 

 perfect syllogism, and have taken it for granted also that he was alive or 

 that he existed, for the last fact must have been just as obvious to himself 

 as the first, and somewhat more so to the world at large. 



There is another logical error in this memorable enthymeme,or syllogism 

 without a head, which ought not to pass without notice ; I mean that the 

 proof does not run parallel with the predicate, and consequently does not 

 answer its purpose. The subject predicated is that the philosopher 

 exists or is alive, and to prove this he affirms gratuitously that he thinks. 



I think ; and therefore I am." Now, in respect to the extent or par- 

 allelism of the proof, he might just as well have said "I itch," or "I 

 eat ; and therefore I am." I will not dispute that in all probability he 

 thought more than he itched, or partook of food : but let us take which 

 proof we will, it could only be a proof so long as he itched, or was eating ; 

 and consequently, whenever he ceased from either of these conditionsj 

 upon his own argument, he would have no proof whatever of being alive. 

 Now, that he must often have ceased from itching, or eating, there is no 

 difficulty in admitting ; but then he may also at times have ceased from 

 thinking, not only in various morbid states of the brain, but whenever he 

 slept without dreamimg. And hence, the utmost that any such argument 

 could decide in his favour, let us take which kind of proof we will, would 

 be that he could alternately prove himself to be alive and alternately not 

 alive ; that it was obvious to himself that he existed for and during the 

 time that he thought, itched, or ate, but that he had no proof of existence 

 as soon as these were over. 



But I have said, that M. Des Cartes' philosophy consists not only in 

 demanding proofs where no proofs are necessary, and where the truisms 

 are so clear as to render it ludicrous to ask for them ; but in taking for 

 granted propositions that evidently demand proof And I now allude to 

 his whole doctrine of innate ideas — of axioms or principles planted in 



