Introduction

The complement to pramāṇa theory is prameya theory. Whereas the pramāṇas are the means of knowledge, the prameyas are the knowables, cognizable entities that constitute the world. With respect to the number and kinds of such entities, there was a very wide variety of opinion among classical Indian philosophers. Moreover, since according to most Indian systems knowledge of reality is at least a necessary condition for liberation, these metaphysical disputes were taken to be of practical as well as theoretical importance.

Ontology is an attempt to answer the question ‘What is there?’ But to answer that question we need to distinguish between two separate, though intertwined, questions: ‘How many entities are there?’ and ‘How many kinds of entities are there?’ In both cases the interesting answers are: ‘One’, ‘Two’, and ‘Many’ (i.e., monism, dualism and pluralism). Note, however, that a position about the number of kinds of entities that exist does not in itself entail any particular position about the number of entities that exist. Nor does a dualism or pluralism about the number of entities itself entail any particular position about the number of kinds of entities.

There were, correspondingly, quite a variety of Indian responses to the question ‘What is there?’, including variants of monism, dualism and pluralism about both entities and kinds. Advaita, for instance, holds that there is numerically only one entity (Brahman/ātman) and that all plurality is illusory. Viśiṣṭādvaita qualifies this monism and maintains that while there exists only one ontologically independent substance (God), there also exist other dependent entities (souls and material entities). Sautrāntika Buddhism, in contrast, holds that there are numerically many entities, but only one kind of thing: momentary particulars (svalakṣaṇas). Yogācāra Buddhism and Cārvāka also agree that there is only one kind of thing, but disagree about whether it is mental or material. Sāṃkhya-Yoga, on the other hand, asserts that reality consists of just two kinds of things but a plurality of entities: many selves (puruṣas) and a single evolving primal matter (prakṛti). Finally, Nyāya-Vaiśeṣika is pluralist about both entities and kinds: there are many kinds in the world, though there are only seven basic ontological categories (padārtha).

Underpinning these disagreements about the nature and number of reals are sometimes also important differences of opinion about the criterion of reality. According to the Buddhists, for instance, to be real is to be causally efficacious.