Interesting Facts

Moral philosophers since David Hume have debated whether values are objective, and thus factual. In A Treatise of Human Nature Hume pointed out there is no obvious way for a series of statements about what ought to be the case to be derived from a series of statements of what is the case. Those who insist there is a logical gulf between facts and values, such that it is fallacious to attempt to derive values from facts, include G. E. Moore, who called attempting to do so the Naturalistic fallacy.
• The factual-counterfactual distinction
Factuality — what has occurred — can also be contrasted with counterfactuality — what might have occurred, but did not. A counterfactual conditional or subjunctive conditional is a conditional (or "if-then") statement indicating what would be the case if events had been other than they actually are. For example, "If Alexander had lived, his empire would have been greater than Rome". This is to be contrasted with an indicative conditional, which indicates what is (in fact) the case if its antecedent is (in fact) true — for example, "if you drink this, it will make you well".
Such sentences are important to Modal logic, especially since the development of Possible world semantics.