Hume's explicit pronouncements about truth are few and unenlightening. In a well-known passage near the beginning of Book III of the Treatise (III i 1; p. 458 in Selby-Bigge's edition) he writes that ‘Reason is the discovery of truth or falsehood. Truth or falsehood consists in an agreement or disagreement either to the real relations of ideas, or to real existence and matter of fact.’ Hume's main concern in this passage, however, is not with the concept of truth, but with his thesis that moral distinctions are not derived from reason: he introduces his reference to truth only with a view to showing that our ‘passions, volitions and actions … being original facts and realities, complete in themselves,’ are not susceptible of the agreement and disagreement spoken of, and therefore cannot be said to be true or false, in conformity with or contrary to reason. The account of truth given here is not elaborated, and perhaps not even thought to need elaboration. Similarly with another passage a few pages earlier in which Hume says that ‘Truth is of two kinds, consisting either in the discovery of the proportions of ideas, considered as such, or in the conformity of our ideas of objects to their real existence’ (T, ii iii 10; 448 SB). Here again his interest is not in truth itself but in ‘curiosity, or the love of truth,’ the passion which, Hume says, ‘was the first source of all our inquiries’ (ibid.). Hume seems to take it for granted that nothing more needs to be said about what it is to discover ‘the proportions of ideas, considered as such,’ or about the circumstances in which we can speak of there being ‘conformity’ or the lack of it between our ideas of objects and their real existence. So far as he is concerned the central point to grasp is the distinction between propositions which have to do with relations of ideas and those which express, or purport to express, matters of fact. Once this distinction is clear, the nature of truth is supposed to be plain.