 Together with the characterization of calibration measures given above, suitable constraints \(C(\sim)\) on the equivalence relation \(\sim\), and two extra assumptions, this norm does establish Probabilism. The extra assumptions are these: First, if our agent has a credence function \(c\) in \(\mathcal{C_F}\), the possible worlds that we are considering include not only all (consistent) truth assignments to \(\mathcal{F}\), but also any (consistent) truth assignments to any (finite) algebra \(\mathcal{F}'\) that extends \(\mathcal{F}\). And, second, given any such \(\mathcal{F}'\), the equivalence relation \(\sim\) can be extended in any possible way, providing the extension \(\sim'\) of \(\sim\) satisfies \(C(\sim')\).