(-sacca, -vacana, -desanā): 'truth (or term, exposition) that is true in the highest (or ultimate) sense', as contrasted with the 'conventional truth' (vohāra-sacca), which is also called 'commonly accepted truth' (sammuti-sacca; in Skr: samvrti-satya).
The Buddha, in explaining his doctrine, sometimes used conventional language and sometimes the philosophical mode of expression which is in accordance with undeluded insight into reality. In that ultimate sense, existence is a mere process of physical and mental phenomena within which, or beyond which, no real ego-entity nor any abiding substance can ever be found. Thus, whenever the suttas speak of man, woman or person, or of the rebirth of a being, this must not be taken as being valid in the ultimate sense, but as a mere conventional mode of speech (vohāra-vacana).
It is one of the main characteristics of the Abhidhamma Pitaka, in distinction from most of the Sutta Pitaka, that it does not employ conventional language, but deals only with ultimates, or realities in the highest sense (paramattha-dhammā). But also in the Sutta Pitaka there are many expositions in terms of ultimate language (paramattha-desanā), namely, wherever these texts deal with the groups (khandha), elements (dhātu) or sense-bases (āyatana), and their components; and wherever the 3 characteristics (ti-lakkhana) are applied. The majority of Sutta texts, however, use the conventional language, as appropriate in a practical or ethical context, because it "would not be right to say that 'the groups' (khandha) feel shame, etc."
It should be noted, however, that also statements of the Buddha couched in conventional language, are called 'truth' (vohāra-sacca), being correct on their own level, which does not contradict the fact that such statements ultimately refer to impermanent and impersonal processes.
The two truths - ultimate and conventional - appear in that form only in the commentaries, but are implied in a sutta-distinction of 'explicit (or direct) meaning' (nītattha, q.v.) and 'implicit meaning (to be inferred)' (neyyattha). Further, the Buddha repeatedly mentioned his reservations when using conventional speech, e.g. in D. 9: "These are merely names, expressions, turns of speech, designations in common use in the world, which the Perfect One (Tathāgata) uses without misapprehending them." See also S. I. 25.
The term paramattha, in the sense here used, occurs in the first para. of the Kathāvatthu, a work of the Abhidhamma Pitaka (s. Guide, p. 62). (App: vohāra).
The commentarial discussions on these truths (Com. to D. 9 and M. 5) have not yet been translated in full. On these see K N. Jayatilleke, Early Buddhist Theory of Knowledge (London, 1963), pp. 361ff.
In Mahāyana, the Mādhyamika school has given a prominent place to the teaching of the two truths.