2′. Whenever John says that X, then X. ( ∀ X:proposition, says(John, X) ⇒ X )
Note that X here is not a statement (grammatically valid sentence?), but a proposition. John can express it however he likes: by means of written word, by means of a demonstration or example, by means of a telepathy, etc. There is no need, specifically, to convert a proposition to a string or vice versa; as long as (1) is true and we most likely understand what proposition John is trying to convey, we will most likely believe in the correct normative proposition (that, if expressed in a statement, requires an “ought”).
Oh, an one more thing. My updated premise 2 is:
2′. Whenever John says that X, then X. ( ∀ X:proposition, says(John, X) ⇒ X )
Note that X here is not a statement (grammatically valid sentence?), but a proposition. John can express it however he likes: by means of written word, by means of a demonstration or example, by means of a telepathy, etc. There is no need, specifically, to convert a proposition to a string or vice versa; as long as (1) is true and we most likely understand what proposition John is trying to convey, we will most likely believe in the correct normative proposition (that, if expressed in a statement, requires an “ought”).