206 REASONING. 



the occult cause of our sensations, do really exist, yet what we call divisi- 

 bility may be an attribute only of our sensations of sight and touch, and 

 not of their uncognizable cause. Divisibilitj'- 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 di- 

 visible, 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 JReview I extract the follow- 

 ing passage. The germ of an idea identical with that of Mr. Spencer may 

 be found in the present chapter, on a pi'eceding page ; but in Mr. Spencer 

 it is not an undeveloped thought, but a philosophical theory. 



" When remembering a certain thing as in a certain place, the place and 

 the thing are mentally represented together ; while to think of the non-ex- 

 istence of the thing in that place implies a consciousness in which the place 

 is represented, but not the thing. Similarly, if instead of thinking of an 

 object as colorless, we think of its having color, the change consists in the 

 addition to the concept of an element that was before absent from it — the 

 object can not 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 generalization of the uni- 

 versal experience that some mental states are directly destructive of other 

 states. It formulates a certain absolutely constant law, that the appearance 

 of any positive mode of consciousness can not occur without excluding a 

 correlative negative mode ; and that the negative mode can not occur with- 

 out excluding the correlative positive mode : the antithesis 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 hei'e 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., 16) identifies the Principle of Contradiction with his Law of 

 Relativity, viz., that ''every thing that can be thought of, every affirmation that can be made, 

 has an opposite or counter notion or affirmation ;" a proposition whicii 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 Examina- 

 tion of Sir William Hamilton's Philosophy. 



