 Many schemes and tropes are such that the innovations they license at a given point depend on what’s mutually understood to be the case for present communicative purposes, what’s implicitly taken to be true or at least truistic, at the point where the innovation occurs. Any such assumption is what Skulsky calls a talk postulate. Something may be a talk postulate because it’s so widely and firmly believed as to be obvious (and obviously obvious), because we’re assuming it for the time being for purposes of argument, or simply because it’s something we routinely pretend to believe in particular conversational settings. The crucial points are three: