The standard mood of sentences used to issue requests and commands. Questions in the philosophy of language arising from imperatives include estimating whether the need to issue requests and commands might be as basic as the need to communicate information (animal signalling systems may often be interpreted either way), and understanding the relationship between commands and other action-guiding uses of language, such as ethical discourse. The ethical theory of prescriptivism in fact equates the two functions. A further question is whether there is an imperative logic. ‘Hump that bale!’ seems to follow from ‘Tote that barge and hump that bale!’ in something like the way that ‘It's raining’ follows from ‘It's windy and it's raining.’ But it is harder to say how to include other forms: does ‘Shut the door or shut the window!’ follow from ‘Shut the window!’, for example? The usual way to develop an imperative logic is to work in terms of the possibility of satisfying the one command without satisfying the other, thereby turning it into a variation of ordinary deductive logic.