Williamson Chapter 4

Understanding-assent link: our sheer linguistic and conceptual competence mandates assent to some sentences or thoughts and inferences

A logical truth is (1) Every Vixen is a Vixen
Sentence (1) can be written as a understanding-assent link as UA1.

UA1: Necessarily, whoever understands the sentence ‘Every vixen is a vixen’ assents to it.

Is UA1 true? If UA1 is true then an armchair methodology of philosophy is based on understanding-assent links.

Williamson’s counterexample is a situation in which a person, A, given sentence (1) infers that (1) entails
(2) There is at least one Vixen
Person A does this through seemingly logical thought, with very good reasons for his belief’s etc.
In this case person A, for background reasons which can be endlessly thought up, denies (2), and so it follows that he also denies (1).
Because A doesn’t assent to (1), under the claim UA1, person A doesn’t understand (1). This seems wrong because a in the situation described person A seems to understand (1) but by some belief of a mistaken theory, or because of certain background belief bred into person A, he doesn’t accept (2).
Williamson claims then that UA1 is false and because of this example nothing is epistemically available only on the bases of linguistic and conceptual competence.

I don’t think this counterexample is very good because it seems as though UA1 has not been proven false because it shouldn’t matter what a person’s view on the matter is when some of their other views are clearly mistaken, no matter how smart or intellectual you imagine them to be. It seems unrealistic that someone denies a logical truth.
Maybe this is too harsh a reading of Williamson, I just didn’t think his example was very convincing.