Two Truths Doctrine

The Buddhist doctrine of the two truths (Wylie: bden pa gnyis) differentiates between two levels of satya (Sanskrit), meaning truth or "really existing" in the discourse of the Budhha: the "conventional" or "provisional" (saṁvṛti) truth, and the "ultimate" (paramārtha) truth.

The exact meaning varies between the various Buddhist schools and traditions. The best known interpretation is from the Madhyamaka school of Mahāyāna Buddhism, whose founder Nagarjuna, originally propounded the doctrine.

The phenomenal world is accorded a provisional existence. The character of the phenomenal world is declared to be neither real nor unreal, but logically indeterminable. The ultimate truth, on the other hand, is posited as elusive to ordinary experience and conceptual thought. Nagarjuna makes a significant use of the earlier Buddhist doctrine of dependent origination (pratītyasamutpāda) to prove the 'emptiness' or 'voidness' of everything, leading to the famous doctrine of 'emptiness', Śūnyatā. The Madhyamaka position concludes that everything is devoid of its own nature, everything is empty.

In Chinese Buddhism, the Madhyamaka position is accepted and the two truths refer to two ontological truths. Reality exists of two levels, a relative level and an absolute level. Based on their understanding of the Mahayana Mahaparinirvana Sutra, the Chinese supposed that the teaching of the Buddha-nature was, as stated by that sutra, the final Buddhist teaching, and that there is an essential truth above sunyata and the two truths.

The śūnyatā doctrine is an attempt to show that it is neither proper nor strictly justifiable to regard any metaphysical system as absolutely valid. It doesn't lead to nihilism but strikes a middle course between excessive naivete and excessive scepticism.

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Wikipedia