Vādanyāya is one of the representative works of Dharmakīrti. It is concerned with debate logic and deals with win-or-lose reasoning rules in the broad sense of logic. In this paper, we will concentrate our discussion on Dharmakīrti’s theory of nigrahasthāna (fault) in his debate logic, a key issue in Vādanyāya. First, we point out that the justification of three logical reasons as proof conditions of debate constitutes the rational point of departure for Dharmakīrti’s debate logic. Second, we analyze the (...) differences between Dharmakīrti’s and the Naiyāyika’s notion of debate and point out that Dharmakīrti’s ‘debate’ involves two parties (the disputant and the opponent) attempting to rationally refute the other’s opinion to persuade the other to change their wrong ideas. Last, based on the discussion of Dharmakīrti’s concept of debate logic, we identify seven types of nigrahasthāna in Vādanyāya with regard to the two parties of a debate (the disputant and the opponent). (shrink)