170 THE PRINCIPLES OF SCIENCE. 



1 . That we acquire a perfect knowledge of the compara- 



tive numbers of balls of each kind within the box. 



2. That the contents of the ballot-box remain unchanged. 

 Of the latter assumption, or rather that concerning the 



constitution of the world which it illustrates, the logician 

 or physicist can have nothing to say. As the Creation of 

 the Universe is necessarily an act passing all experience 

 and all conception, so any change in that Creation, or, it 

 may be, a termination of it, must likewise be infinitely be- 

 yond the bounds of our mental faculties. No science, no 

 reasoning upon the subject, can have any validity ; for 

 without experience we are without the basis and materials 

 of knowledge. It is the fundamental postulate accordingly 

 of all inference concerning the future, that there shall be 

 no arbitrary change in the subject of inference ; of the pro- 

 bability or improbability of such a change I conceive that 

 our faculties can give no estimate. 



The other condition of inductive inference that we 

 acquire an approximately complete knowledge of the 

 combinations in which events do occur, is at least in some 

 degree within the bounds of our perceptive and mental 

 powers. There are many branches of science in which 

 phenomena seem to be governed by conditions of a most 

 fixed and general character. We have much ground in 

 such cases for believing that the future occurrence of 

 such phenomena may be calculated and predicted. But 

 the whole question now becomes one of probability and 

 improbability. We leave the region of pure logic to enter 

 one in which the number of events is the ground of 

 inference. We do not leave the region of logic ; we only 

 leave that where certainty, affirmative or negative, is the 

 result, and the agreement or disagreement of qualities the 

 means of inference. For the future, number and quantity 

 will enter into most of our processes of reasoning ; but then 

 I hold that number and quantity are but portions of the 



