Can logic cure human prejudice? The radical skepticism of the Buddhist philosopher Dignāga

Ideas & Philosophy · Published 3 October 2026 Swipe more like this →

In short: Dignāga, an Indian philosopher active around 470 to 540 CE, revolutionized logic by arguing that human knowledge relies solely on raw sensation and conceptual inference. He proposed that our minds constantly misinterpret reality through language, suggesting that rigorous logical standards are the ultimate tool to dismantle deep-seated dogmatism and prejudice.

Dignāga’s magnum opus, the Pramāṇa-samuccaya, established a system where knowledge is derived from only two sources: perception (pratyakṣa) and inference (anumāna). Perception is defined as non-conceptual, unstructured sense data—the immediate awareness of particulars like a patch of color or hardness. Because this raw experience is pre-verbal, Dignāga argued it is inherently inerrant. Errors only arise when the mind later interprets these sensations, grouping them into complex, named objects that do not exist in the raw data.

The second pillar of his system, inference, is the process of using linguistic conventions and conceptual structures to understand general attributes. Dignāga developed a strict set of criteria for valid evidence, requiring that an inferential sign must be present in the subject, present in at least one similar locus, and absent in all dissimilar loci. Richard Hayes, a modern scholar, suggests these criteria are so demanding that they function as a form of rational skepticism. By setting standards that few human judgments can meet, Dignāga aimed to force thinkers to remain humble and open to revising their views.

Dignāga also introduced the theory of apoha, or 'exclusion,' to explain how language functions. He argued that words do not denote real universals or individuals; instead, they define objects solely by what they are not. For instance, calling something a 'cow' simply excludes everything that is not a cow. This nominalist approach challenged the orthodox Hindu schools of his time, which relied on the existence of universals. Today, studying Dignāga remains difficult because his original Sanskrit texts are largely lost, forcing scholars to reconstruct his ideas from Tibetan and Chinese translations and the critiques of his later opponents.

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