t84 



REASONING. 



bute only of our sensations of sight 

 and touch, and not of their uncognis- 

 able cause. Divisibility may not be 

 predicable at all, in any intelligible 

 sense, of Things in Themselves, nor 

 therefore of Matter in itself ; and 

 the assumed necessity of being either 

 infinitely or finitely divisible may be 

 an inapplicable alternative. On this 

 question I am happy to have the full 

 concurrence of Mr. Herbert Spencer, 

 from whose paper in the Fortnightly 

 Review I extract the following pas- 

 sage. The germ of an idea identical 

 with that of Mr. Spencer may be 

 found in the present chapter, about 

 a page back, but in Mr. Spencer it 

 is not an undeveloped thought, but 

 a philosophical theory. 



"When rememberingacertain thing 

 as in a certain place, the place and the 

 thing are mentally represented toge- 

 ther ; while to think of the non-exis- 

 tence of the thing in that place implies 

 a consciousness in which the place is 

 represented, but not the thing. Simi- 

 larly, if instead of thinking of an ob- 

 ject as colourless, we think of its 

 having colour, the change consists in 

 the addition to the concept of an 

 element that was before absent from 

 it — the object cannot be thought of 

 first as red and then as not red, 

 without one component of the thought 



being totally expelled from the mind 

 by another. The law of the Excluded 

 Middle, then, is simply a generalisa- 

 tion of the universal experience that 

 some mental states are directly de- 

 structive of other states. It formu- 

 lates a certain absolutely constant 

 law, that the appearance of any posi- 

 tive mode of consciousness cannot 

 occur without excluding a correlative 

 negative mode ; and that the negative 

 mode cannot occur without excluding 

 the correlative positive mode, the an- 

 tithesis of positive and negative being, 

 indeed, merely an expression of this 

 experience. Hence it follows that if 

 consciousness is not in one of the two 

 modes it must be in the other." * 



I must here close this supplementary 

 chapter, and with it the Second Book. 

 The Theory of Induction, in the most 

 comprehensive sense of the term, will 

 form the subject of the Third. 



* Professor Bain {Logic, i. i6) identifies 

 the Principle of Contradiction with hia 

 Law of Relativity, viz. that "everything 

 that can be thought of, every affirmation 

 that can be made, has an opposite or 

 counter notion or aifirmation ; " a propo- 

 sition which is one of the general results 

 of the whole body of human experience. 

 For further considerations respecting the 

 axioms of Contradiction and Excluded 

 Middle, see the twenty-first chapter of 

 An Examination of Sir Williani Hamilton'$ 

 Philosophy, 



