 Gaṅgeśa argues that tarka is useful for—as we might say these days—reëstablishing a presumption of truth in favor of one or another thesis brought into doubt. For example, by supposing the truth of an opponent’s thesis and showing how it leads to unacceptable consequences, one repossesses a presumption of truth, provided one’s own thesis is supported by at least the appearance of a knowledge source and, further, that it has not itself been ruled out. Thus tarka comprises arguments that are not in themselves knowledge-generators but capable nonetheless of showing what we should and should not believe. In particular, reasoning can show “untoward ramifications” (prasaṅga) of not accepting a conclusion that is evidenced, Gaṅgeśa says. Forms of tarka such as self-contradiction, infinite regress, and circular reasoning are employed in the dialogic exchanges constructed in the Jewel and other works of later and indeed early Nyāya philosophy and, for that matter, all the philosophic schools.