Abstract: This paper examines a specific type of error in Classical Indian philosophy: a person with a visual disorder called timira sees a single moon as two.
On the one hand, it plays a crucial role in the Buddhist epistemologists’ discussions of pseudo-perception and the definition of perception. Nevertheless, it was initially overlooked in Dignāga’s (ca. 480–540) Pramāṇasamuccaya: it does not appear explicitly in its classification of pseudo-perception (pratyakṣābhāsa), nor is it ruled out by his definition of perception (kalpanāpoḍha, “free from conceptualization”). Yet it receives significant attention from Dharmakīrti (ca. 600–660) and his followers. In Dharmakīrti’s typology of pseudo-perception in the Pramāṇavārttika, non-conceptual pseudo-perception, as illustrated by the double-moon error, is recognized as a distinct type. In his later works, Dharmakīrti further revises Dignāga’s definition of perception by adding the criterion of “non-erroneous” (abhrānta). To reconcile Dignāga’s and Dharmakīrti’s positions on this issue, Prajñākaragupta (8th–9th century), in his Pramāṇavārttikālaṅkāra (PVA), draws on the grammatical principles of utsarga (general rule) and apavāda (specific delimitation).
In Dharmakīrtian literature, this double-moon error also functions as a philosophical metaphor for broader epistemological issues. Dharmakīrti and his followers often cite the case of two people suffering from timira who agree on the second moon they see, even though what they perceive is nothing but internal images of their own cognitions and that second moon has no external counterpart. In the Santānāntarasiddhi, Dharmakīrti uses this example to show how an idealist can infer another person’s mental series from that person’s bodily and verbal actions. In the Tattvasaṅgraha, together with the Pañjikā, Śāntarakṣita (725–788) and Kamalaśīla (740–795) use this example similarly, but to explain the mechanism of linguistic communication. In the PVA, Prajñākaragupta uses it differently, to show how two distinct cognitions, i.e., sense and mental perception, may coexist yet be apprehended as one.
About the speaker: Qingyang Huang is a PhD candidate at EPHE–PSL in Paris, jointly supervised by Prof. Vincent Eltschinger and Prof. Isabelle Ratié. Her research focuses on metaphysics, epistemology, and the philosophy of religion in Classical India, particularly theories of perception and error in Buddhist–Brahmanical polemical exchanges. She also works on early Tibetan translations of the Indian Buddhist epistemological corpus (11th–13th centuries).