THEORIES CONCERNING AXIOMS. 



m 



one mode of production of a pheno- 

 menon often suffices to make every 

 other mode appear inconceivable. 

 Whatever connects two ideas by a 

 strong association may, and conti- 

 nually does, render their separation 

 in thoiaght impossible ; as Mr. Spencer 

 in other parts of his speculations fre- 

 quently recognises. It was not for 

 want of experience that the Cartesians 

 were unable to conceive that one body 

 could produce motion in another with- 

 out contact. They had as much ex- 

 perience of other modes of producing 

 motion as they had of that mode. 

 The planets had revolved, and heavy 

 bodies had fallen, every hour of their 

 lives. But they fancied these pheno- 

 mena to be produced by a hidden 

 machinery which they did not see, 

 because without it they were unable 

 to conceive what they did see. The 

 inconcei vableness, insteadof represent- 

 ing their experience, dominated and 

 overrode their experience. Without 

 dwelling further on what I have 

 termed the positive argument of Mr, | 

 Spencer in support of his criterion of ' 

 truth, I pass to his negative argument, j 

 on which he lays more stress. 



§ 3. The negative argument is, 

 that, whether inconceivability be good 

 evidence or bad, no stronger evidence 

 is to be obtained. That what is in- 

 conceivable cannot be true is postu- 

 lated in every act of thought It is 

 the foundation of all our original 

 premises. Still more it is assumed in 

 all conclusions from those premisea 

 The invariability of belief, tested by 

 the inconceivableness of its negation, 

 "is our sole warrant for every de- 

 monstration. Logic is simply a sjrste- 

 matisation of the process by which we 

 indirectly obtain this warrant for 

 beliefs that do not directly possess it. 

 To gain the strongest conviction pos- 

 sible respecting any complex fact, we 

 either analytically descend from it by 

 successive steps, each of which we 

 unconsciously test by the inconceiv- 

 ableness of its negation, until we reach 

 lome axiom or truth which we have 



similarly tested ; or we synthetically 

 ascend from such axiom or truth by 

 such steps. In either case we connect 

 some isolated belief with a belief 

 which invariably exists by a series of 

 intermediate beliefs which invariably 

 exist." The following passage sums 

 up the theory : *' When we perceive 

 that the negation of the belief is incon- 

 ceivable, we have all possible warrant 

 for asserting the invariability of its 

 existence ; and in asserting this, we 

 express alike our logical justification 

 of it, and the inexorable necessity we 



are under of holding it We 



have seen that this is the assumption 

 on which every conclusion whatever 

 xUtimately rests. We have no other 

 guarantee for the reality of conscious- 

 ness, of sensations, of personal exist- 

 ence ; we have no other guarantee for 

 any axiom ; we have no other guar- 

 antee for any step in a demonstration. 

 Hence, as being taken for granted in 

 every act of the understanding, it 

 must be regarded as the Universal 

 Postulate." But as this postulate 

 which we are under an "inexorable 

 j necessity " of holding true, is some- 

 [ times false ; as •* beliefs that once 

 I were shown by the inconceivableness 

 '■ of their negations to invariably exist 

 have since been found untrue," and 

 I as " beliefs that now possess this char- 

 { acter may some day share the same 

 fate ; " the canon of belief laid down 

 by Mr. Spencer, is, that "the most 

 certain conclusion " is that ** which 

 involves the postulate the fewest 

 times." Reasoning, therefore, never 

 ought to prevail against one of the 

 immediate beliefs, (the belief inMatter, 

 in the outward reality of Extension, 

 Space, and the like,) because each of 

 these involves the postulate only once; 

 while an argument, besides involving 

 it in the premises, involves it again in 

 every step of the ratiocination, no one 

 of the successive acts of inference 

 being recognised as valid except 

 because we cannot conceive the con- 

 clusion not to follow from the pre- 

 mises. 



It will be convenient to take the 



