The lesson is familiar. Kripke’s arguments in favor of a posteriori necessary truths annul the idea that conceivability is a guide to metaphysical possibility because determining that which is a priori is a separate issue from determining that which is necessary. Modal rationalists do not completely agree with this conclusion. Following recent work on two-dimensional semantics, David Chalmers suggests that two distinct semantic values can be assigned to a statement, depending on whether we consider possible worlds as counterfactual or counteractual. (...) The idea is that counterfactual possibilities yield familiar Kripkean intuitions, but that counteractuals fulfill the desired link between a priori conceivability and metaphysical possibility. In this paper, I discuss a problem for modalrationalism that arises through the use of material conditionals, or conditionals in the indicative mood. I then turn to Chalmers’ response, and suggest reasons why it is inadequate. I turn to another response from Chalmers, and suggest that, whilst it solves the fi rst issue, it is incapable of grounding modal rationalism. In conclusion I will suggest a way in which a tempered version of modal rationalism can be salvaged. (shrink)