SCIENCE AND NATURE 21 



will seems divided against itself ; I then speak of the 

 antagonistic wills as if they were those of two different 

 persons. If I act in a way which is contrary to my 

 normal will, I say that " I was not myself." This feeling 

 that " I " am practically indistinguishable from my will, 

 and that what is not subject to my will is not me, is 

 undoubtedly one of the main reasons for referring sensa- 

 tions, which are often wholly independent of my will, 

 to a foreign and external world. It has also, as we shall 

 see, a bearing on the second and more important difference 

 between sensations and other thoughts, to which we must 

 turn next. 



This second difference is that other people agree with 

 me much more closely about sensations than they do 

 about any other kind of thought. The fact, expressed 

 in that manner, is extremely familiar. If I am in a room 

 when the electric light bulb bursts, not only I, but every- 

 one else in the room (unless some of them are blind or 

 deaf), hears the explosion and experiences the change 

 from light to darkness. On the other hand, apart from 

 sensations, we may all have been thinking about different 

 things, remembering different things, following different 

 trains of reasoning, and experiencing different desires. 

 This community of sensations, contrasted with the 

 particularity of other kinds of thoughts, leads naturally 

 to the view that the sensations are determined by some- 

 thing that is not me or you or anybody else in the room, 

 but is something external to us all ; while the other 

 thoughts, which we do not share, are parts of the 

 particular person, experiencing them. This simple ex- 

 perience is probably the main reason why we have come 

 to believe so firmly that there is an external world and 

 that our perceptions received by our senses give us 

 information about it. 



For this is the test which we apply in practice when any 

 doubt arises if we are experiencing sensations which give 



