If moral claims are not propositions, then propositional logic doesn’t work on them — notably, this means that a moral claim could never be the conclusion of a logical proof.
Which would stop us from deriving new moral claims from existing ones. I understand now. Thanks!
So, if I understand correctly now, non-cognitivists say that human morals aren’t constrained by the rules of logic. People don’t care much about contradictions between their moral beliefs, they don’t try to reduce them to consistent and independent axioms, they don’t try to find new rules implied by old ones. They just cheer and boo certain things.
It’s worth noting that there are non-cognitivist positions other than emotivism (the “boo, murder!” position). For instance, there’s the prescriptivist position — that moral claims are imperative sentences or commands. This is also non-cognitivist, because commands are not propositions and don’t have truth-values. But it’s not emotivist, since we can do a kind of logic on commands, even though it’s not the same as the logic on propositions.
(“Boo, murder!” does not logically entail “Boo, murdering John!” … but the command “Don’t murder people!” conjoined with the proposition “John is a person.” does seem to logically entail the command “Don’t murder John!” So conjunction of commands and propositions works. But disjunction on commands doesn’t work.)
If moral claims are not propositions, then propositional logic doesn’t work on them — notably, this means that a moral claim could never be the conclusion of a logical proof.
Which would stop us from deriving new moral claims from existing ones. I understand now. Thanks!
So, if I understand correctly now, non-cognitivists say that human morals aren’t constrained by the rules of logic. People don’t care much about contradictions between their moral beliefs, they don’t try to reduce them to consistent and independent axioms, they don’t try to find new rules implied by old ones. They just cheer and boo certain things.
It’s worth noting that there are non-cognitivist positions other than emotivism (the “boo, murder!” position). For instance, there’s the prescriptivist position — that moral claims are imperative sentences or commands. This is also non-cognitivist, because commands are not propositions and don’t have truth-values. But it’s not emotivist, since we can do a kind of logic on commands, even though it’s not the same as the logic on propositions.
https://en.wikipedia.org/wiki/Non-cognitivism
https://en.wikipedia.org/wiki/Imperative_logic
(“Boo, murder!” does not logically entail “Boo, murdering John!” … but the command “Don’t murder people!” conjoined with the proposition “John is a person.” does seem to logically entail the command “Don’t murder John!” So conjunction of commands and propositions works. But disjunction on commands doesn’t work.)