262 THE PRINCIPLES OF SCIENCE. 



association, or any rude process of inference, infer the 

 future directly from the past, it is the work of logic to 

 analyse the conditions on which the correctness of this 

 inference depends. Even Mr. Mill would admit that such 

 analysis involves the consideration of general truths 11 , and 

 in this, as in several other important points, we might 

 controvert Mr. Mill's own views by his own statements. 



On the Grounds of Inductive Inference. 



I hold that, in all cases of inductive inference, we must 

 invent hypotheses, until we fall upon some hypothesis 

 which yields deductive results in accordance with experi- 

 ence. Such accordance renders the chosen hypothesis 

 more or less probable, and we may then deduce, with some 

 degree of likelihood, the nature of our future experience, on 

 the assumption that no arbitrary change takes place in 

 the conditions of nature. We can o.nly .argue from the 

 past to the future, on the general principle set forth in the 

 commencement of this work, that what is true of a thing 

 will be true of the like. So far then as one object or 

 event differs from another, all inference is impossible ; 

 particulars as particulars can no more make an inference 

 than grains of sand can make a rope. We must always 

 rise to something which is general or same in the cases, 

 and assuming that sameness to be extended to new cases 

 we learn their nature. Hearing a clock tick five thousand 

 times without exception or variation, we adopt the very 

 probable hypothesis that there is some invariably acting 

 machine which produces those uniform sounds, and which 

 will, in the absence of change, go on producing them. 

 Meeting twenty times with a bright yellow ductile sub- 

 stance, and finding it to be always very heavy and in- 

 corrodible, I infer that there was some natural condition, 



11 ' System of Logic/ bk. II. chap. iii. 5. pp. 225, &c. 



