18 WHAT IS SCIENCE? 



purely internal and totally unrelated to the external 

 world. Indeed, it is such thoughts which give rise to 

 the idea of a perceiver who perceives the external world. 

 For I regard all my perceptions as "my" perceptions, 

 because they are all connected together by thoughts of 

 other kinds. Thus I can remember my perceptions and 

 call them to mind ; I can think about them and compare 

 one with another ; I can judge that they are pleasant 

 or unpleasant and desire that some and not others should 

 recur. These thoughts about my perceptions I regard 

 as characteristically internal to me ; they are just the 

 things which make up " me " ; once more, it is these 

 thoughts about my perceptions which make me regard 

 them as " my " perceptions. It is very difficult to convey 

 these sentiments in words, just because, as has been said 

 already, all words assume these sentiments. But I hope 

 that any reader who considers the matter will agree that 

 the conception of an external world, which I perceive, 

 is founded as much on the idea that there are thoughts 

 which are wholly part of me, and have nothing to do 

 with the external world, as on the idea that there are 

 other thoughts which, though they are also part of me, 

 are intimately connected with the external world, and 

 inform me of that world. 



If this view can be grasped, the basis of the doubts 

 that we are considering becomes clear. Some of my 

 thoughts I regard as wholly internal ; others, forming 

 the special class of sensations or perceptions received 

 through the organs of sense, I regard as rather part of 

 the external world. Why, it may be asked relevantly, 

 do I make this distinction ? If it is necessary to regard 

 some of my thoughts as wholly internal and giving 

 evidence about me and not about the external world, 

 why do I not so regard all my thoughts ? If one class 

 of my thoughts does/ not give any information about an 

 external world or even any evidence that there is such 



