  The terms in this definition require explanation. The technical sense of ‘ascription’ (āropa) is ‘counterfactual or suppositional cognition’ (āhāryāropa), defined as a cognition whose qualifier is an property the opposite of which is known to reside in the qualificand. In other words, it is a counterfactual assumption. ‘Pervader’ and ‘pervaded’ are notions taken from the Nyāya theory of inference. When we say that wherever there is smoke, there is fire, this can be re-expressed as that fire pervades smoke, i.e. that the property of being a smoke-possessing-thing has a narrower extension than the property of being a fire-possessing-thing. So here, fire is the pervader and smoke is the pervaded. Thus, tarka consists in a cognition of smoke’s absence given the counterfactual assumption that fire is absent. It is the cognition of a conditional “if p then q”, or “were p to be true then q would be true”, assuming that ‘p’ is false.