 The grammaticality of an expression, on the standard generative Essentialist view, is the status conferred on it by the competence state of an ideal speaker. But competence can never be exercised or used without potentially interfering performance factors like memory being exercised as well. This means that judgments about grammaticality are never really directly available to the linguist through informant judgments: they have to be inferred from judgments of acceptability (along with any other relevant evidence). Nevertheless, Essentialists do take acceptability judgments to provide fairly good evidence concerning the character of linguistic competence. In fact the use of informally gathered acceptability judgment data is a hallmark of post-1965 Essentialist practice.