The Problem of Nacre-Silver (Sukti-Rupya) in Indian Philosophy

Summary

Bratindra Kumar Sengupta’s article explores one of the classic examples used in Indian philosophy to analyse erroneous cognition: mistaking a mother‑of‑pearl shell (nacre) for a piece of silver. Along with the similar case of mistaking a rope for a snake, this example illustrates how a person can perceive an object incorrectly yet act upon that false perception as if it were real. Sengupta notes that Indian thinkers from different schools have used the nacre‑silver illusion as an archetype to explain the nature of error, the relation between perception and memory, and the criteria for true knowledge. He surveys a range of views collectively known as khyāti‑vāda, or theories of erroneous cognition. The Nyāya school terms the error anyathā‑khyāti: according to it, the cognition itself is correct (one does perceive something bright), but the error lies in misattributing it to the wrong object. The Prābhākara Mīmāṃsā school proposes bhedāgraha, the ‘non-recognition of difference’: perception and memory are valid in themselves, but error arises because one fails to distinguish between them in action and expression; thus the knowledge is not false, but our behaviour is. Kumārila Bhaṭṭa’s Bhāṭṭa Mīmāṃsā calls the error akhyāti: it argues that the simultaneous apprehension of object and recollection is impossible, so one part of the false cognition is actually a recollection mistaken for present perception. The Buddhist Vijñānavāda holds asat‑khyāti: the perceived silver is entirely unreal; what is experienced is a false appearance projected by consciousness. The Sāṃkhyas propose sat‑khyāti: the silver perceived is real but belongs to a different place and time; the mind superimposes it due to the predominance of sattva guṇa. Advaita Vedānta advances anirvacanīya‑khyāti: the false silver is indescribable as either real or unreal; ignorance projects an illusory object that is sublated by true knowledge. Sengupta examines the arguments and counter‑arguments among these schools, discussing how each interprets the roles of perception, memory, similarity and imagination in producing illusion. He emphasises that the debate is not merely about a shell and a piece of silver but about the epistemological status of the world and the possibility of distinguishing reality from appearance. By comparing the schools systematically, the article highlights the sophistication of Indian logic and the persistent relevance of its questions to problems of psychology and metaphysics.