This comprehensive study explains Atmatattvaviveka, Udayanacharya’s rigorous Nyaya inquiry into the existence and nature of the self. It situates the Sanskrit treatise within medieval Mithila, the developing Nyaya-Vaisheshika tradition, and the uncertain chronology of Udayanacharya’s life. It clarifies Nyaya concepts such as atman, manas, pramana, samskara, memory, recognition, agency, and liberation. The discussion reconstructs how…