* ON ANCIENT AND MODERN SKEPTICS. 369 



must be acknowledged concerning the other ;'* and he is so confident of the 

 truth of this maxim, that he makes it one of the pillars of his philosophy 

 To those who may be inclined to admit this maxim on his authority, I would 

 propose a few plain questions. Do you feel any, even the least, warmth in 

 the idea of a bonfire, a burning mountain, or the general conflagration 1 Do 

 you feel more real cold in Virgil's Scythian winter than in Milton's description 

 of the flames of hell ? Do you acknowledge that to be true of the idea of 

 eating, which is certainly true of the impression of it, that it alleviates hun- 

 ger, fills the belly, and contributes to the support of human life 1 If you 

 answer these questions in the negative, you deny one of the fundamental 

 principles of this philosophy. We have, it is true, a livelier perception of a 

 friend when we see him, than when we think of him in his absence : but this 

 is not all : every person of a sound mind knows, that in the one case we be- 

 lieve, and are certain, that the object exists, and is present with us ; in the 

 other we believe, and are certain, that the object is not present : which, how- 

 ever, they must deny who maintain that an idea differs from an impression 

 only in being weaker, and in no other respect whatsoever. 



"That every idea should be a copy and resemblance of the impression 

 whence it is derived ; that, for example, the idea of red should be a red idea ; 

 the idea of a roaring lion a roaring idea; the idea of an ass, a hairy, long- 

 eared, sluggish idea, patient of labour, and much addicted to thistles ; that 

 the idea of extension should be extended, and that of solidity solid ; that a 

 thought of the mind should be endued with all, or any, of the qualities of 

 matter ; is, in my judgment, inconceivable and impossible. Yet our author 

 takes it for granted ; and it is another of his fundamental maxims. Such is 

 the credulity of skepticism !" 



It is a singular coincidence, that while the substantive existence of an ex- 

 ternal world was thus hotly attacked by metaphysics, the science of physics 

 should have proved just as adverse to it ; thus reviving, as we have already 

 seen, the very same double assault to which it had been exposed at Athens, 

 shortly after the establishment of the Academy. This latter controversy 

 commenced and hinged upon what are the real qualities of matter. Heat, 

 cold, colours, smell, taste, and sounds had been pretty generally banished 

 from the list about the middle of the seventeenth century. Locke contended, 

 after Sir Isaac Newton, for solidity, extension, mobility, and figure : but it 

 was soon found that there is a great difficulty in granting it solidity : that the 

 particles of bodies never come into actual contact, or influence each other 

 by the means of objective pressure ; that however apparently solid the mass 

 to which they belong, such mass may be reduced to a smaller bulk by cold, 

 as it may be "increased in bulk by heat ; that we can hence form no concep- 

 tion of perfect solidity, and every fact in nature appears to disprove its ex- 

 istence. The minutest corpuscle we can pick out is capable of a minuter 

 division, and the parts into which it divides possessing the common nature 

 of the corpuscle which has produced them, must necessarily be capable of a 

 still farther division ; and, as such divisions can have no assignable limit, 

 matter must necessarily and essentially be divisible to infinity. For these 

 and similar reasons M. Boscovich contended that there is no such thing as 

 solidity in matter ; nor any thing more than simple, unextended, indivisible 

 points, possessing the powers of attraction and repulsion, yet producing ex- 

 tension by their combination.! 



Upon the self-contradiction of this hypothesis I have found it necessary to 

 comment on a former occasion ;| and shall now, therefore, only farther ob- 

 serve, that it just as completely sweeps the whole of matter away with a 

 physical broom, as the systems of Berkeley and Hume do with a metaphy- 

 sical; for, by leaving us nothing but unextended points, possessing mere 

 powers without a substrate, it leaves nothing at all, a world, indeed, but a 



* Treatise on Human Nature, vol. i. p. 41. t Theoria Philosophise Naturalis, Vien. 1758. 



$ Series i. Lecture iii. See also Dr. Wollaston's paper " On the finite Extent of the Atmosphsre, 1 * 

 Phil. Trans. 1822, p. 8. 



A a 



