»70 ANTIENT METAPHYSICS. Book III. 



truly a great fecret of nature, which can be known to none but na- 

 tural philofophers; and it is certainly a mofl wonderful phacno- 

 menon of nature, by which the rays of light, refledted from the ob- 

 ject at the diftance perhaps of millions of miles, are conveyed to our 

 eyes entire, and without being mixed with other rays. The fame 

 may be faid of the idea of the fenfation oi found, which is convey- 

 ed to our ears from a diftance of miles through the medium of 

 the air, and conveyed entire and without being mixed with other 

 founds; and this is certainly likewife a wonderful phaenomenon, 

 though a very common one. Of the fenfation oi fmcllhig the idea 

 is more obvious, as the fmell is not conveyed to us from fo great a 

 diftance : And the ideas of touching and tajlhtg, being produc- 

 ed by objects of fenfe in contact with our organs, are ftill more 

 eafily conceived. And thus, I think, I have Ihown that we have 

 truly ideas of /enfat'ion, though very different from what Mr Locke 

 calls ideas of fenfation. As to what he calls, not improperly, ideas of 

 refleElion^ they are fuch, no doubt, as he fuppofes them to be : But 

 he does not tell us from what fource they are derived, viz. from the 

 confcioufnefs that we have of the operations of our mind j which 

 may be faid to be the eflential difference betwixt us and the brutes, 

 and the foundation of all arts and fciences, and particularly of the 

 moft valuable fcience of mind, of which we know nothing but by 

 refleding upon the operations of our own mind, and by what we 

 can infer with refped to other minds from thefe operations. 



CHAP. 



