Buddhist logico-epistemology

Buddhist logico-epistemology is a term used in Western scholarship to describe Buddhist systems of pramāṇa (epistemic tool, valid cognition) and hetu-vidya (reasoning, logic).

While the term may refer to various Buddhist systems and views on reasoning and epistemology, it is most often used to refer to the work of the "Epistemological school" (Sanskrit: Pramāṇa-vāda), i.e., the school of Dignaga and Dharmakirti which developed from the 5th through 7th centuries and remained the main system of Buddhist reasoning until the decline of Buddhism in India.

The early Buddhist texts show that the historical Buddha was familiar with certain rules of reasoning used for debating purposes and made use of these against his opponents. He also seems to have held certain ideas about epistemology and reasoning, though he did not put forth a logico-epistemological system.

The Theravada Kathāvatthu contains some rules on debate and reasoning. The first Buddhist thinker to discuss logical and epistemic issues systematically was Vasubandhu in his Vāda-vidhi (A Method for Argumentation). A mature system of Buddhist logic and epistemology was founded by the Buddhist scholar Dignāga (c. 480–540 CE) in his magnum opus, the Pramāṇa-samuccaya. Dharmakirti further developed this system with several innovations in his Pramanavarttika ("Commentary on Valid Cognition"). His work was influential on all later Buddhist philosophical systems as well as on numerous Hindu thinkers. It also became the main source of epistemology and reasoning in Tibetan Buddhism.

Scholars such as H.N. Randle and Fyodor Shcherbatskoy (1930s) initially employed terms such as “Indian Logic” and “Buddhist Logic” to refer to the Indian tradition of inference (anumāna), epistemology (pramana), and "science of causes" (hetu-vidyā). This tradition developed in the orthodox Hindu tradition known as Nyaya as well as in Buddhist philosophy. Logic in classical India, writes Bimal Krishna Matilal, is "the systematic study of informal inference-patterns, the rules of debate, the identification of sound inference vis-à-vis sophistical argument, and similar topics." As Matilal notes, this tradition developed out of systematic debate theory (vadavidyā):

Logic as the study of the form of correct arguments and inference patterns, developed in India from the methodology of philosophical debate. The art of conducting a philosophical debate was prevalent probably as early as the time of the Buddha and the Mahavira (Jina), but it became more systematic and methodical a few hundred years later.

"Indian Logic" is a different system than modern derivatives of classical logic (such as modern predicate calculus): anumāna-theory, a system in its own right. "Indian Logic" was also influenced by the study of grammar, whereas Classical Logic—which principally informed modern Western Logic—was influenced by the study of mathematics.

A key difference between Western Logic and Indian Logic is that certain epistemological issues are included within Indian Logic, whereas in modern Western Logic they are deliberately excluded. Indian Logic includes general questions regarding the "nature of the derivation of knowledge," epistemology, from information supplied by evidence, evidence which in turn may be another item of knowledge. For this reason, other scholars use the term "logico-epistemology" to refer to this tradition, emphasizing the centrality of the epistemic project for Indian logical reasoning. According to Georges Dreyfus, while Western logic tends to be focused on formal validity and deduction: