223 THE PRINCIPLES OF SCIENCE. [CHAP, 



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

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

 seems to me undesirable in a systematic work like this to 

 enter into controversy at any length, or to attempt to refute 

 the views of other logicians. But I shall feel bound to 

 state, in a separate publication, my very deliberate opinion 

 that many of Mill's innovations in logical science, and 

 especially his doctrine of reasoning from particulars to 

 particulars, are entirely groundless and false. 



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 only argue from the 

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

 tion, we adopt the very probable hypothesis that there is 

 some invariably acting machine which produces those uni- 

 form sounds, and which will, in the absence of change, go 

 on producing them. Meeting twenty times with a bright 

 yellow ductile substance, and finding it always to be very 

 heavy and incorrodible, I infer that there was some natural 

 condition which tended in the creation of things to asso- 

 ciate these properties together, and I expect to find them 

 associated in the next instance. But there always is the 

 possibility that some unknown change may take place 

 between past and future cases. The clock may run down, 

 or be subject to a hundred accidents altering its condition. 

 There is no reason in the nature of things, so far as known 



