64 SCIENTIFIC METHOD IN PHILOSOPHY 



what he means by " reality," and may be asked how 

 their unreality follows from the supposed reality of his 

 super-sensible world. In answering these questions, he 

 is led to a logic which merges into that of Parmenides 

 and Plato and the idealist tradition. 



The logic of the idealist tradition has gradually grown 

 very complex and very abstruse, as may be seen from the 

 Bradleian sample considered in our first lecture. If we 

 attempted to deal fully with this logic, we should not 

 have time to reach any other aspect of our subject ; we 

 will therefore, while acknowledging that it deserves a 

 long discussion, pass by its central doctrines with only 

 such occasional criticism as may serve to exemplify other 

 topics, and concentrate our attention on such matters as 

 its objections to the continuity of motion and the 

 infinity of space and time objections which have been 

 fully answered by modern mathematicians in a manner 

 constituting an abiding triumph for the method of 

 logical analysis in philosophy. These objections and the 

 modern answers to them will occupy our fifth, sixth, and 

 seventh lectures. 



Berkeley's attack, as reinforced by the physiology of 

 the sense-organs and nerves and brain, is very power- 

 ful. I think it must be admitted as probable that the 

 immediate objects of sense depend for their existence 

 upon physiological conditions in ourselves, and that, for 

 example, the coloured surfaces which we see cease to exist 

 when we shut our eyes. But it would be a mistake to 

 infer that they are dependent upon mind, not real while 

 we see them, or not the sole basis for our knowledge 

 of the external world. This line of argument will be 

 developed in the present lecture. 



The discrepancy between the world of physics and 

 the world of sense, which we shall consider in our fourth 



