An Indian Theory of Defeasible Reasoning

The anonymous pre-Gagea Navya-Nyya treatise Updhidarpaa (UD) deals exclusively with the so-called updhi, a key concept in the Navya-Nyya 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-Nyya doctrine of updhi and modern logical theories such as John L. Pollocks 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 authors attempt to define all candidate updhis by means of a general defining characteristic (smnyalakaa) which is a property of itself. He advocates a non-well-founded property concept and distances himself from what is communis opinio in Nyya, viz. that self-dependence (tmraya) is a kind of absurdity. No such discussion concerning the problem of foundation in the Navya-Nyya logic of property and location is to be found in the later Updhivda of Gageas Tattavacintmai.