Arthâpatti is a pervasive form of reasoning investigated by Indian philosophers in order to think about unseen causes and interpret ordinary and religious language. Its nature is a point of controversy among Mimamsa, Nyaya, and Buddhist philosophers, yet, to date, it has received less attention than perception, inference, and testimony. This collection presents a one-of-a-kind reference resource for understanding this form of reasoning studied in Indian philosophy. Assembling translations of central primary texts together with newly-commissioned essays on research topics, it features a significant introductory essay. Readable translations of Sanskrit works are accompanied by critical notes that introduce arthâpatti, offer historical context, and clarify the philosophical debates surrounding it. Showing how arthâpatti is used as a way to reason about the basic unseen causes driving language use, cause-and-effect relationships, as well as to interpret ambiguous or figurative texts, this book demonstrates the importance of this epistemic instrument in both contemporary Anglo-analytic and classical Indian epistemology, language, and logic.