28 THE PRINCIPLES OF SCIENCE. [CHAP. 



redness ; but this latter term has one single meaning the 

 quality alone. Thus it arises that abstract terms are in- 

 capadle of plurality. Ked ohjects are numerically distinct 

 each from each, and there are multitudes of such objects ; 

 but redness is a single quality which runs through all 

 those objects, and is the same in one as it is in another. 

 It is true that we muy speak of rednesses, meaning different 

 kinds or tints of redness, just as we may speak of colours, 

 meaning different kinds of colours. But in distinguishing 

 kinds, degrees, or other differences, we render the terms so 

 far concrete. In that they are merely red there is but a 

 single nature in red objects, and so far as things are merely 

 coloured, colour is a single indivisible quality. Kedness, 

 so far as it is redness merely, is one and the same every- 

 where, and possesses absolute oneness. In virtue of this 

 unity we acquire the power of treating all instances of 

 such quality as we may treat any one. We possess, in 

 short, general knowledge. 



Substantial Terms. 



Logicians appear to have taken little notice of a class of 

 terms which partake in certain respects of the character of 

 abstract terms and yet are undoubtedly the names of con- 

 crete existing things. These terms are the names of 

 substances, such as gold, carbonate of lime, nitrogen, &c. 

 We cannot speak of two golds, twenty carbonates of lime, 

 or a hundred nitrogens. There is no such distinction 

 between the parts of a uniform substance as will allow of 

 a discrimination of numerous individuals. The qualities of 

 colour, lustre, malleability, density, &c., by which we 

 recognise gold, extend through its substance irrespective of 

 particular size or shape. So far as a substance is gold, it 

 is one and the same everywhere ; so that terms of this 

 kind, which I propose to call substantial terms, possess 

 the peculiar unity of abstract terms. Yet they are not 

 abstract; for gold is of course a tangible visible body, 

 entirely concrete, and existing independently of other 

 bodies. 



It is only when, by actual mechanical division, we break 

 up the uniform whole which forms the meaning of a 

 substantial term, that we introduce number. Piece of gold 



