There are, as we have seen, certain structural properties that are necessary conditions on rational belief. What exactly these are depends on your views. However, there are further ways of assessing belief. Strongly believing true things and strongly believing the negations of false things seem like good-making-features of beliefs. For the case of precise credences, we can make this precise. There is a large literature on “scoring rules”: methods for measuring how good a probability is relative to the actual state of the world (Brier 1950; Savage 1971; Joyce 2009; Pettigrew 2011). These are numerical methods of measuring how good a probability is given the true state of the world.