ON HUMAN UNDERSTANDING. 347 



It is not to be supposed that mankind could consent to be inoculated with 

 this disease to any great extent, or for any considerable period of time . and 

 hence the chief hypotheses that were countenanced at Rome, and till the de- 

 cline of the Roman empire, were those of Plato, Aristotle, and Epicurus. 

 During the dark ages, Aristotle seems to have held an undivided sovereignty ; 

 and though his competitors came in for a share of power upon the revival of 

 literature, he still held possession of the majority of the schools, till, in. the 

 middle of the seventeenth century, Des Cartes introduced a new hypothesis, 

 which served as a foundation for most of the systems or speculations which 

 have appeared since. 



With Aristotle and Epicurus Des Cartes contended that the mind perceives 

 external objects by images or resemblances presented to it: these images he 

 called, after Plato, ideas ; though he neither acceded to the meaning of this 

 term as given by Plato, nor allowed with Aristotle or Epicurus that they pro- 

 need from the objects themselves, and are transmitted to the mind through the 

 channel of the senses ; so that the precise signification he attached to this term 

 is not clear. With Epicurus he threw away the doctrine of an intellectual 

 world ; but contended, in order to supply its place, that the mind has a large 

 stock of ideas of its own. implanted by the hand of nature, and not derived 

 from the world around us : ideas, therefore, that are strictly innate, and may 

 be found on being searched for, though otherwise not necessarily present to 

 the mind's contemplation. Among these the principal are, the idea of thought, 

 or consciousness, of God, and of matter; all which maybe fully depended 

 upon as so many established truths : and hence, upon his hypothesis, all real 

 knowledge flows from an internal source, or, in other words, from the mind 

 itself. These ideas can never deceive us, though the senses may do so in 

 their report concerning external objects ; and, consequently, such ideas are 

 chiefly to be trusted to and reasoned from even in questions that relate to the 

 senses. 



In analyzing 1 the idea of THOUGHT, the mind, according to Aristotle, dis- 

 covers it to be a power that has neither extension, figure, local motion, nor 

 any other property commonly ascribed to body. In analyzing the idea of 

 GOD, the mind finds piesented to it a being necessarily and eternally existing, 

 supremely intelligent, powerful, and perfect, the fountain of all goodness and 

 truth, and the creator of the universe. In analyzing the idea of MATTER, the 

 mind perceives it to be a substance possessing no other property than ex- 

 tent : or, in other words, as having nothing else belonging to it than length, 

 breadth, and thickness ; that space, possessing equally this property, is a part 

 of matter, and consequently that matter is universal, and there is no vacuum. 

 From these, and other innate ideas, compared and combined with the ideas 

 of sensation, or those furnished to the mind by the senses, flows, on the hy- 

 pothesis of Des Cartes, the whole fund of human understanding, or all the 

 knowledge that mankind are or can be possessed of. 



There are two fundamental errors, and errors, moreover, of an opposite 

 character, that accompany, or rather introduce, this hypothesis, and to which, 

 popular as it was at one time, it has at length completely fallen a sacrifice : 

 these are the attempting to prove what ought to be taken for granted, and the 

 taking for granted what ought to be proved. 



The philosophy of Des Cartes sets off with supposing that every man is 

 more or less under the influence of prejudice, and consequently that he cannot 

 know the real truth of any thing till he has thoroughly sifted it. It follows, 

 necessarily, as a second position, that every man ought, at least once in his 

 life, to doubt of every thing, in order to sift it; not, however, like the skep- 

 tics of Greece, that, by such examination, he may be confirmed in doubt, but 

 that, by obtaining proofs, he may have a settled conviction. 



Full fraught with these preliminary principles, our philosopher opens his 

 career of knowledge, and while he himself continues as grave as the noble 

 knight of La Mancha, his journey commences almost as ludicrously. His 

 first doubt is, whether he himself is alive or in being, and his next, whether 

 any body is alive or in being about him. He soon satisfies himself, however, 



