The view that First Order Morality sentences are not Truth Apt Specifically, it is saying that Statements cannot themselves be interpreted as Statements, but rather they are similar to Questions and Commands. Every sentence is used to express & reveal an attitude. Thereby, they prove that there are no Truth Apt Propositions at all, and therefore nothing can be considered Knowledge. The point of Moral Language is to then non-verbally express your attitudes.
The only true statement that non-cognitivists believe in is the Second Order Morality claim that no Moral Facts are Truth Apt.
Support For Non-Cognitivism
It is wrong to kill means the same as Don’t Kill. Non-cognitivists say that the surface grammar does not make the actual Proposition
This mismatch is what non-cognitivists spend most their time proving - proving that a statement actually means another thing.