This problem known as the ‘is–ought gap’ is one of explaining how truths about what ought to be the case – that is, about what we are morally obliged to do (or to avoid doing) – might derive from truths about what is the case. Scottish philosopher David Hume (1711–1776) thought we should be wary of making inferences like ‘such and such is a certain way therefore we ought to do this and that’ because it’s hard to see how such inferences could be valid. The claim that ‘you can’t get an ought from an is’ is therefore also known as ‘Hume’s law’.
Think about the kinds of arguments you hear each day. Often people infer statements about how things should or can be, based on a fact about how things are. Someone might say: ‘humans have always eaten meat, therefore it’s ok for them to go on doing so’. The problem is that the inferred statement (conclusion) only follows from the first statement if we add in another linking statement, something like: ‘it’s ok for humans to continue doing whatever they’ve done in the past’. The trouble is though, not only are those linking statements often contestable, it’s also unclear how we might justify them, since they themselves contain statements about what ought – or is permitted – to be the case! We thus appear stuck at an impasse. Most of us think there are facts about obligations, but explaining how those facts arise is quite tricky. If we appeal to further facts about obligations, we haven’t really got anywhere, but if we appeal to facts about how things are, we seem to have committed a fallacy. | |||