[1] [Greek αἴτιον τοῦ ψευδοῦς (aition tou pseudous) = the cause of the error. Tr.] Definitions of cause: a. As a ‘philosophical’ relation. 295. As the outcome of his doctrine, he submits two definitions of the relation of cause and effect. Considering it as ‘a _philosophical_ relation or comparison of two ideas, we may define a cause to be an object precedent and contiguous to another, and where all objects resembling the former are placed in like relations of precedency and contiguity to those objects that resemble the latter.’ Considering the relation as ‘a _natural_ one, or as an association between ideas,’ we may say that ‘a _cause_ is an object precedent and contiguous to another, and so united with it that the idea of one determines the mind to form the idea of the other, and the impression of the one to form a more lively idea of the other’. [1] [1] P. 464. [Book I, part III., sec. XIV.] Is Hume entitled to retain ‘philosophical’ relations as distinct from ‘natural’? 296. Our first enquiry must be how far these definitions are really consistent with the theory from which they are derived. At the outset, it is a surprise to find that the ‘philosophical relation’ of cause and effect, as distinct from the natural one, should still appear to survive. Such a distinction has no meaning unless it implies a conceived relation of objects other than the _de facto_ sequence of feelings, of which one ‘naturally’ introduces the other. It is the characteristic of Locke’s doctrine of knowledge that in it this distinction is still latent. His language constantly implies that knowledge, as a perception of relations, is other than the sequence of feelings; but by confining his view chiefly to relation in the way of likeness and unlikeness--a relation that exists between feelings merely as felt, or as they are for the feeling consciousness--he avoids the necessity of deciding what the ‘ideas’ are in the connection of which knowledge and reasoning consist, whether objects constituted by conceived relations or feelings suggestive of each other. But when once attention had been fixed, as it was by Hume, on an ostensible relation between objects, like that of cause and effect, which, if it exist at all, is clearly not one in the way of resemblance between feelings, the distinction spoken of becomes patent. If the colour red had not the likeness and unlikeness which it has to the colour blue, the colours would be different feelings from what they are; but if the flame of fire and its heat were not regarded severally as cause and effect, it would make no difference to them as feelings; or, to put it conversely, it is not upon any comparison of two feelings with each other that we regard them as related in the way of cause and effect. In what sense then can the relation between flame and heat be a philosophical relation, as defined by Hume--a relation in virtue of which we compare objects, or an idea that we acquire upon comparison?