 The guiding idea is that in making an assertion the speaker is trying to get the audience to rule out certain possibilities. In asserting ‘It’s cold today’, for instance, I may be trying to get you to rule out possibilities in which today’s temperature in Melbourne is over 10° C. We can model what my assertion conveys, then, as a function that maps possible worlds in which today’s temperature is under 10° C to True and all other worlds to False. However, the precise truth-conditions communicated by an assertoric use of a sentence depend in part on the conversational context in which it takes place. Just which temperatures count as cold, for instance, depends on shared background assumptions in a particular conversational context: what’s cold in Melbourne is mild in Manitoba.