Chap.II. ANTIENT METAPHYSICS. 8i 



I will give fome examples of this diftindion Lctivixt Senfations 

 and Ideas in qualities ; and my fir ft example fliall be of a Colour, 

 fuch as •white : For, as it is by Colour that the face of Nature ap- 

 pears to us, I think it is not improper to begin with an example ta- 

 ken from it. 



Thofe, who know no more of phllofophy than what is to be learn- 

 ed from the works of Mr Locke, will think it ftrange that I {hould 

 fpeak of the Idea of a Colour ; for Mr Locke tells us, that all fuch 

 perceptions of Senfe are fimple Ideas, (fo he calls Senfations), which 

 therefore cannot be defined ; and, if fo, it is clear, that they can- 

 not be Ideas, in my fenfe of the word. The admirers, therefore, of • 

 Mr Locke, will be difpofed to ridicule me as much, as he has en- 

 deavoured to ridicule Ariftotle for his definition of Motion. But 

 it is Mr Locke that has made himfelf ridiculous, not Ariftotle, by 

 pretending to philofophife, without being able to diftinguifh betwixt 

 a Senfation ar\d the Idea of a Senfation. The Senfation itfelf cer- 

 tainly cannot be defined, becaufe it is a Senfation, and not an Idea : 

 But the Idea of a Senfation may be explained by definition, as well 

 as every other Idea, being the operation of Intelled; and it is to 

 be defined in the manner I have juft now mentioned, by which all 

 Senfations are to be defined. The Senfation of White is nothing 

 but the perception by the Senfe of Sight of a patch of light upon 

 any fuperficies, more or lefs bright, as the Colour is more or lefs 

 pure. This Senfation, though preferved in the Phantafia, and con- 

 ceived to exift in many different obje£ts, is not the Idea of this Co- 

 lour : What makes a perfedt and fcicntlfical Idea of it is well known 

 to the optician ; for he knows that it is the refledion of all the rays 

 of light, without feparation or difcrimlnatlon, which, being collec- 

 t-ed and refra£ted in the pupil of the eye, and forming an image 

 upon the retina, gives a perception of this Colour. But the vulgar 

 liave the Idea of White as well as the philofopher, though not near 

 Vol. IL L ' fo 



