26 WHAT IS SCIENCE? 



possible to base on the existence of other people an argu- 

 ment for and a criterion of the external world, without 

 lapsing into the fallacy of a circular argument which 

 assumes what it pretends to prove. As we shall see in a 

 moment, it is not relevant to our inquiry to decide whether 

 such arguments are justified or, indeed, whether it is 

 possible to produce any valid arguments for the existence 

 of other people and of the external world. All that I 

 am concerned with here is to draw attention to the ideas 

 which undoubtedly underlie our habitual and common- 

 sense distinction between the internal and the external 

 world, or between other people and ourselves, on the 

 one hand, and nature on the other. The ideas which 

 are important for our further inquiry are : 



1. That the conception of " myself," on which is 

 founded the conception of all other people, is intimately 

 connected with the mental experiences which we call will 

 or volition. A person is something that wills ; volition 

 is the test of personality ; nothing is a person or has 

 personality (at least of the human type) unless it is 

 characterized by a will ; all exercise of will is inseparable 

 from the recognition of a person who exercises it ; and 

 everything that is directly subject to the same will is 

 part of the same person. 



2. Our belief in the external world, or at least of that 

 part of it which is called " nature," is based on our 

 perceptions received through our sense organs. And we 

 believe that these perceptions inform us of the external 

 world, partly because they are independent of our wills, 

 but more because other people agree with us in those 

 sensations. 



3. Our belief in other people is based on an analogy 

 between the behaviour of their bodies and the behaviour 

 of our own. If the actions of other bodies are similar 

 to those of our own, and if those actions in our bodies are 

 accompanied by certain thoughts in our minds, then we 



