 Once impossible worlds enter the stage, (P) becomes false from right to left. We therefore need a principle that restricts the quantification in the right half of the biconditional to possible worlds. How to do that, without appealing to modal notions, is not straightforward. The hybrid account (Berto 2010) has the advantage here. If possible worlds are all and only the genuine ones, with impossible worlds as ersatz constructions of some kind, then we can capture the intent of (P) as: