MENTAL PROCESSES BY WHICH WE EVOLVE NEW TRUTHS. 337 



An examination of these instances will illustrate the 

 mental processes by means of which the maximum amount 

 of new knowledge is extracted from the original state- 

 ment, 'All metals are some heat-conductors,' and will 

 also show that the knowledge implicitly contained or 

 hidden in it, is evolved or made explicit by means of com- 

 parison, division, subtraction, combination, permutation, 

 and transformation of ideas. Thus, in forming the first im- 

 mediate inference, we abstract or fix our attention alone 

 upon the word ' heat,' and imagine it in its logical aspect 

 only, i.e., as a mere existence. In forming the second, we 

 abstract the same term, but think of heat only as a force. 

 In forming the third, we proceed similarly, but contemplate 

 heat in a mechanical aspect only as a mode of motion ; 

 and in the fourth we also proceed similarly, but think of 

 heat as that kind of motion which we term vibration. In 

 the fifth we fix our ideas only upon the term ' some.' and 

 transform it into its equivalent idea, ' a part of,' or 

 ' species.' In the sixth, we compare the ideas or terms, 

 ' some ' and ' all.' In the seventh, we transform the idea 

 of ( heat-conductors ' into the equivalent one of bodies 

 possessing ' heat-conducting power ; ' and we reverse the 

 order of the terms of the proposition into that of fi some 

 heat-conductors are all metals,' upon the principle that 

 such reversal makes no logical difference. In the eighth, 

 we divide the compound idea ' all metals ' into ' any 

 metal individually.' In the ninth, we abstract the idea 

 of 'copper' from that of ( all metals.' In the tenth, 

 we imagine the negative or contradictory idea of 'all 

 metals,' viz. ' no metals.' In the eleventh, we imagine 

 the idea of ' any statement which includes ' that contradic- 

 tory conception. In the twelfth, we divide off and ab- 

 stract the idea of ' some metals ' from that of ' all metals,' 

 and imagine the contradictory of ' heat-conductors.' In 



