92 THE FOUNDATIONS OF SCIENCE 



sun has risen every yesterday it will rise to-morrow, 

 and in science it is necessary to assume that an 

 electric current, as in the past, will always exert a 

 magnetic force. The inductive principle of pre- 

 diction cannot be proved by experience, for, as 

 regards future cases, it is the inductive principle 

 alone which can justify any inference from past cases. 

 The principle of induction, then, is itself involved in 

 any attempted proof of it which appeals to experi- 

 ence. Hence, like the laws of thought, it must be 

 accepted on its intrinsic evidence as a piece of in- 

 tuitive knowledge. We feel instinctively that any 

 event which has occurred before may recur again, 

 and that, the oftener it has occurred before with no 

 exception, the greater the probability of its recur- 

 rence : and there we must leave it. 



We have now completed our circuit of the sciences, 

 and have returned to our starting-point, where logic 

 and mathematics are applied to the study of nature, 

 and especially, and in the first place, to that aspect 

 of nature given by mechanics. 



And here our brief survey of an inexhaustible field 

 must close. It is contrary to our aim to examine 

 into the details of any one science. It is also beyond 

 our mark to deal with the metaphysical problems 

 of the nature of reality, which need all knowledge for 

 their study and are represented in our original 

 diagram by the spot of blinding white light at the 

 centre. 



