338 PERSONAL PREPARATION FOR RESEARCH. 



the thirteenth, we permutate and transform the ideas of 

 4 all metals are some heat-conductors,' into their logical 

 equivalent, 4 some heat-conductors are all metals,' and then 

 imagine its complete contradictory, viz., 4 all heat-con- 

 ductors are non-metals.' In the fourteenth we also first 

 reverse the order of the ideas, and form the equivalent 

 statement 4 some heat-conductors are all metals,' and then 

 show by comparison that the statement ' all heat-con- 

 ductors are metals,' exceeds the former, and therefore 

 contradicts it. In the fifteenth, we also permutate the 

 ideas similarly, and then by comparison show that the 

 statement, 'some heat-conductors are all metals,' is 'a 

 true one.' In the sixteenth, we transform the ideas of 

 * all metals,' and of 4 heat-conductors,' into their contra- 

 dictories of 4 no metal ' and ' non-conductor of heat,' 

 and then make a positive statement which is equivalent 

 to the original one, upon the principle that the reversal 

 of meaning of both of the terms of a proposition has no 

 logical effect, and in accordance with the saying that 

 4 two negatives make a positive.' In the seventeenth, 

 we first reverse the order of the terms of the proposition 

 by placing the idea of 4 metals ' last, and then proceed 

 exactly as in the sixteenth instance. In the eighteenth, 

 we abstract, or fix our attention alone upon the existence 

 of the action called 4 conduction of heat,' which must occur 

 in all 4 heat-conductors.' In the nineteenth, we abstract 

 the same idea of conduction, and then imagine it only as 

 4 a means by which heat is transmitted.' And in the 

 twentieth, we merely employ the subject and predicate of 

 the proposition as parts of a more complex conception. Jn 

 all these cases, whether we analyse the proposition, per- 

 mutate its ideas, transform it, or draw inferences from it, 

 we substitute inclusive ideas, and explicitly state what the 

 original proposition implicitly contained. 



