Abstract
Every kind of ‘ought’ implies some kind of ‘can’ – but there are many kinds of ‘ought’ and even more kinds of ‘can’. In this essay, I shall focus on a particular kind of ‘ought’ – specifically, on what I shall call the “rational ‘ought’”. On every occasion of use, this kind of ‘ought’ is focused on the situation of a particular agent at a particular time; but this kind of ‘ought’ is concerned, not with how that agent acts at that time, but with what beliefs or intentions the agent has at the time, or with the sort of reasoning by means of which the agent at that time forms or revises those beliefs or intentions