True ideas are those that correspond to a standard. This standard could be a system of axioms, as in mathematics or logic, or it could be, and by default usually is, reality. Let’s look at some claims about the world, and then evaluate their truth. I’m going to look at five types of claim: definition claims, theoretical claims, empirical claims, moral claims and aesthetic claims. I’ll be using Hume’s fact-value distinction to classify them. This is not an exhaustive list; but it should still be insightful because I think it covers the major bases.