Quick questions on The fact-value distinction explained: H2 Knowledge and Inquiry

Hume noticed that writers often proceed through factual claims about what is and then, suddenly, slip into claims about what ought to be, without explaining the transition. His point is logical: you cannot validly derive a normative conclusion from purely descriptive premises, because the conclusion contains an evaluative term (ought) that appears nowhere in the premises, and a valid argument cannot have in its conclusion what is wholly absent from its premises. To reach an ought you need at least one evaluative premise. This is the is-ought gap, and as a point about validity it is widely accepted.

The distinction faces challenges. The most important comes from thick ethical concepts such as cruel, courageous, generous and just. These seem to be descriptive and evaluative at once: to call an act cruel is both to describe it (deliberate infliction of suffering) and to condemn it, and you cannot cleanly peel the evaluation off the description. If thick concepts entangle fact and value, then a sharp metaphysical dichotomy between the two looks doubtful.

State Hume's is-ought gap as a point about valid inference. [6 marks]

Explain Moore's open-question argument and what it is meant to show. [8 marks]

Explain how thick ethical concepts challenge a sharp fact-value separation. [6 marks]