118 THE PRINCIPLES OF SCIENCE. [chap. 



The Nature of Inference. 



The question, What is Inference ? is involved, even to 

 the present day, in as much uncertainty as that ancient 

 question, What is Truth ? I shall in more than one part 

 of this work endeavour to show that inference never does 

 more than explicate, unfold, or develop the information 

 contained in certain premises or facts. Neither in deduc- 

 tive nor inductive reasoning can we add a tittle to our 

 implicit knowledge, which is like that contained in an 

 unread book or a sealed letter. Sir W. Hamilton has well 

 said, "Eeasoning is the showing out explicitly that a 

 propositioai not granted or supposed, is implicitly contained 

 in something different, which is granted or supposed." ^ 



Professor Bo wen has explained ^ with much clearness 

 that tlie conclusion of an argument states explicitly what is 

 virtually or implicitly thought. " The process of reasoning 

 is not so much a mode of evolving a new truth, as it is of 

 establishing or proving an old one, by showing how much 

 was admitted in the concession of the two premises taken 

 together." It is true that the whole meaning of these 

 statements rests upon that of such words as " explicit," 

 " implicit," " virtual." That is implicit which is wrapped 

 up, and we render it explicit when we unfold it. Just as 

 the conception of a circle involves a hundred important 

 geometrical properties, all following from what we know, 

 if we have acuteness to unfold the results, so every fact 

 and statement involves more meaning than seems at first 

 sight. Reasoning explicates or brings to conscious posses- 

 sion what was before imconscious. It does not create, nor 

 does it destroy, but it transmutes and throws the same 

 matter into a new form. 



The difficult question still remains. Where does novelty 

 of form begin ? Is it a case of inference when we pass 

 from " Sincerity is the parent of truth " to "The parent of 

 truth is sincerity?" The old logicians would have called 

 this change conversion, one case of immediate inference. But 

 as all identity is necessaiily reciprocal, and the very 

 meaning of such a proposition is that the two terms are 



^ Loctiires on Mcta])hysics, vol. iv. p. 369. 



^ iiowen, 7V«;a<ise o/t io^ic, Cambridge, U.S., 1866; \> 762. 



