xi Belief in an external World. 215 



external to self. The belief in the existence of the 

 external world is secondary (in logical order, though 

 probably not in the order of development) to the 

 belief in the permanent self; for consciousness of 

 self is, and the belief in an external world is not, a 

 condition of all thought whatever. But they have 

 not only the same degree but the same kind of 

 certainty. We do not here need to enter on the 

 question of the nature of material substance. As 

 Berkeley showed long ago, the deepest metaphysical 

 analysis proves that matter can be interpreted only 

 in terms of sensation and thought ; and it is equally 

 true that the highest physical science of our time 

 tends to merge the idea of matter in that of force. 

 There is an unsolved and insoluble mystery about 

 the nature of the material world, no less than about 

 the nature of our personality. As self is made known 

 to itself by the diversity of its sensations, so is the 

 external world made known by the experience of a 

 multitude of sensations (it would be more intelligible, 

 though less accurate, to say perceptions), whereof the 

 coexistences and successions are not determined by 

 our own thought or our own will. The belief in the 

 existence of an external world, is the affirmation of 

 the judgment that what does not originate within 

 must come from without ; and this, like the belief in 

 personal identity, is not only instinctive but logical ; 

 it cannot be denied without self-contradiction. 



This belief is independent of any opinion as to 

 the nature of the external world. If, with Mill, we 



