An Indian Theory of Defeasible Reasoning The Doctrine of Upadhi in the Upadhidarpana - Harvard Oriental Series

The anonymous pre-Gaṅgesa Navya-Nyaya treatise Upadhidarpaṇa (UD) deals exclusively with the so-called upadhi, a key concept in the Navya-Nyaya theory of inference. The present volume contains the first published edition and translation of the only extant manuscript of the UD. Numerous notes have been added to the translation in order to elucidate the contents and to give a clue to the historical context, as regards authors, works, and philosophical doctrines that are referenced in the UD. Moreover, an extensive introductory chapter provides new insights into relations between the Navya-Nyaya doctrine of upadhi and modern logical theories such as John L. Pollock's theory of defeasible reasoning and property theories, especially property adaptations of well-founded and non-well-founded set theories.

A very intriguing aspect of the UD is the author's attempt to define all candidate upadhis by means of a "general defining characteristic" (samanyalakṣaṇa) which is a property of itself. He advocates a non-well-founded property concept and distances himself from what is communis opinio in Nyaya, viz. that self-dependence (atmasraya) is a kind of absurdity. No such discussion concerning the problem of foundation in the Navya-Nyaya logic of property and location is to be found in the later Upadhivada of Gaṅgesa's Tattavacintamaṇi.