342 DEVELOPMENT AND PURPOSE CHAP. 



elements in our experience, is one that may be formulated 

 in several ways. But however formulated, it comes down 

 to this that the attachments of any element, its relations, 

 that is to say, to other elements, be these relations in space, 

 or in time, or relations of any other kind, are dependent 

 on the character of the elements considered. Thus, if we 

 take any two elements as A and B in a given relation, we 

 have on our assumption two alternatives. This relation 

 may be dependent on the character of A and B as such, 

 and on nothing else. If this is so in the fullest sense, it 

 follows that the relation must be mutual or convertible. 

 A is such that if we trace out the constituents of its char- 

 acter in full, we find ourselves led to the assertion or recog- 

 nition of B in the relation to A originally postulated, and 

 the converse result happens if we start from B. B as such 

 involves A. The simplest illustrations of such a relation 

 are to be seen in certain cases of continuity and in the 

 more elementary relations of time, space and quantity 

 the constructive relations, as they may be generically 

 called. The simplest case of all is one in which the two 

 terms in ordinary speech coalesce into one. It is that of 

 the persistent identity which is the basis of our idea of 

 substance. Suppose our term A to be something existing 

 in time and dependent for its existence on no conditions 

 outside itself. Then its own nature A which conserves it 

 in time for as short a duration as we choose to take, con- 

 serves it indefinitely. The second term of the relation B 

 is simply the existence of the same thing at any subsequent 

 point of time, and this is necessitated by A alone, while A 

 a pre-existing phase is similarly inferable from B. The 

 one term is the other produced forwards or backwards in 

 time. It may be said that we never in experience actually 

 achieve knowledge of substance that is, of such self-con- 

 tained existence. There are always conditions, X, many 

 of them unknown, on which the persistence of A in reality 

 depends. But this is not for the moment the point in 

 question. We have simply to illustrate the meaning of 

 an < as such relation.' We may easily be mistaken in taking 

 for them relations which are in fact contingent. But the 

 mistake consists in attributing a self-contained existence to 



