Hume says you cannot get a moral conclusion from purely factual premises, and that this move is made constantly without being noticed.
But it seems like facts often settle moral questions. If I show that something causes suffering, surely I have shown it is wrong?
Accepted Answer
Your example has a hidden premise, and finding it is the whole exercise.
"This causes suffering, therefore it is wrong" is not valid as it stands. It becomes valid once you add "causing suffering is wrong", and that added line is not a fact about the world. It is a moral claim.
Hume's observation is that arguments of this shape always need such a line, and that writers slide it in without noticing. The conclusion contains something the premises did not.
This does not make facts irrelevant to ethics. It means facts do the work only once a value is already in play. Show that a policy causes suffering and you have settled a great deal, for anyone who already holds that suffering matters.
Worth flagging that this is contested rather than settled, since most summaries present it as established.
Searle argued in 1964 that promising gets you across the gap: the fact that someone made a promise generates an obligation without a smuggled premise. Others reply that the institution of promising has the value built into it already.
Naturalists go further and argue that moral facts just are natural facts of a certain kind, which would dissolve the gap rather than bridge it.
So the useful version for an essay is not "Hume proved this". It is that the burden is on anyone crossing the gap to show how.
The passage itself is short and worth reading directly. Hume only says he has noticed authors changing from "is" to "ought" without explanation and that a reason should be given. He does not claim it is impossible.
The discussion on each answer is open to members.
Join free to read the rest