34 THE PRINCIPLES OF SCIENCE. 



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. 

 Eedness, so far as it is redness merely, is one and the 

 same everywhere, and possesses absolute oneness or unity. 

 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 very little notice of a 

 large class of terms which partake in certain respects of 

 the character of abstract terms and yet are undoubtedly 

 the names of concrete 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 sub- 

 stance 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 every- 

 where ; 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 

 physically independent of other bodies. 



It is only when we break up, by actual mechanical 

 division, the uniform whole which forms the meaning of 

 a substantial term, that we introduce the notion of 

 number. Piece of gold is a term capable of plurality ; 

 for there may be an endless variety of pieces discriminated 



