The cardinality objection to David Lewis's modal realism

According to David Lewis's extreme modal realism, every way that a world co uld be is a way that some concretely existing physical world really is. But if the worlds are physical entities, then there should be a set of all wor lds, whereas I show that in fact the collection of all possible worlds is n ot a set. The latter conclusion remains true even outside of the Lewisian f ramework.