26 DOGMATISM AND EVOLUTION 



of by those unskillful in optics .... Every one is himself the 

 best judge of what he perceives and what not. In vain shall all 

 the mathematicians in the world tell me that I perceive certain 

 lines and angles which introduce into my mind the various ideas 

 of distance, so long as I myself am conscious of no such thing."i 

 The true explanation he finds in the sensations set up by the 

 muscular contraction involved in converging the two eyes. His 

 language here is equally interesting. "It remains that we inquire 

 what ideas or sensations there be that attend vision, unto which 

 we may suppose the ideas of distance are connected, and by 

 which they are introduced into the mind. And, first, it is certain 

 by experience, that when we look at a near object with both eyes, 

 according as it approaches or recedes from us, we alter the dis- 

 position of our eyes, by lessening or widening the distance be- 

 tween the pupils. This disposition or turn of the eyes is attended 

 with a sensation, which seems to me to be that which in this case 

 brings the idea of greater or lesser distance into the mind. Not 

 that there is any natural or necessary connection between the 

 sensation we perceive by the turn of the eyes and greater or 

 lesser distance. But because the mind has, by constant ex- 

 perience, found the different sensations corresponding to the dif- 

 ferent dispositions of the eyes to be attended each with a different 

 degree of distance in the object there has grown an habitual 

 or customary connexion between those two sorts of ideas;" 2 just 

 as, for example, the sound of a word becomes associated with its 

 meaning. Here we have what is at least a plausible theory, 

 based upon a genuine introspection. 



It is with the confidence born of this improved method of 

 introspection, that Berkeley ventures to question the existence 

 in the mind of a distinct class of abstract general ideas over and 

 above particular ideas. Here his polemic is directed against 

 Locke; but at the same time it attacks the very foundations of 

 (intuitionalistic) rationalism. For the essential mark of an intui- 

 tion, and that which distinguishes it from an impression of the 



l An Essay Towards a New Theory of Vision, 10, 12. 

 *Ibid., 16, 17- 



