Writing at page 174 of his book, Our Knowledge of Fact and Value, Hall makes the point that

Our moral and aesthetic judgments are not about our emotions; they are renditions of our emotions, having the same object as our emotions have, saying (in part) exactly what our emotions say. They are expressions of emotions.

Here, it seems to me, is the crux of Hall's claims about value and our knowledge of it. He seems to want to say that valuing is just the expression of our emotions and that emotion language is like descriptive language (contra Hume) in that both are directed at objects, both refer and thus both types of language say something that is determinable from the facts. But there are certain differences in the logic he notes, for descriptive statements are true or false based on the adequacy with which they depict the facts which our perceptions capture for us while:

Evaluative sentences in conventional language receive whatever probability they have from their truthfulness to emotions.

He adds

I need not remark that the 'truthfulness' to which I refer is not correctness of depiction but faithfulness of translation.

In this way, Hall sets out to explode the Humean account which severs fact from value. . .