ciT. xxvri.] GENERALISATION. 505 



men? May we not argue that because some men die 

 therefore he must? Is it requisite to ascend by incbiction 

 to the general proposition " all men must die," and then 

 descend by deduction from that general proposition to tlie 

 case of Mr. Gladstone ? My answer undoubtedly is that 

 we must ascend to general propositions. The fundamental 

 principle of the substitution of similars gives us no wan ant 

 in affirming of Mr. Gladstone what we know of other men, 

 because we cannot be sure that Mr. Gladstone is exactly 

 similar to other men. Until his death we cannot be per- 

 fectly sure that he possesses all the attributes of other 

 men ; it is a question of probability, and I have endeavoured 

 to explain tlie mode in which the theory of probability is 

 applied to calculate the prol)ability that from a series of 

 similar events we may infer the I'eenrrence of like events 

 under identical circumstances. There is then no snch 

 process as that of inferring from particulars to particulars. 

 A careful analysis of the conditions under Mdiich such an 

 inference appears to be made, shows that the process is 

 really a general one, and that what is inferred of a par- 

 ticular case might be inferred of all similar cases. All 

 reasoning is essentially general, and all science implies 

 generalisation. In the very birth-time of philosophy this 

 was held to be so : " Nulla scientia est de individuis, sed 

 de solis universalibus," was the doctrine of Plato, delivered 

 by Porphyry. And Aristotle^ held a like opinion — 

 OvBe/jLia Be re-)(vr} aKO'nel to KaB' eKaarov . . . to 8e Ka6' 

 exaarov aireipov kui ovk eTTio-TTjrov. " No art treats of 

 particular cases ; for particulars are infinite and cannot be 

 known." No one who holds the doctrine that reasoning 

 may Ije from particulars to particidars, can be supposed 

 to have tlie must rudimentary notion of what constitutes 

 reasoning and science. 



At the same time there can be no doubt tliat practi- 

 cally what we find to be true of many similar objects will 

 |)robably be true of the next similar object. This is the 

 result to which an analysis of the Inverse jMethod of 

 I^robabilities leads us, and, in the absence of precise data 

 from winch we may calculate probabilities, we are usually 

 obliged to make a rough assumption that similars in some 



' Aristotle's Rhetoric, Liber I. 2. 11. 



Q Q 2 



