Modal rationalism includes the thesis that ideal primary positive conceivability entails primary possibility. Modal monism is the thesis that the space of logically possible worlds is coextensive with the space of metaphysically possible worlds. In this paper I explore the relation between the two theses. My aim is to show that the former thesis implies the latter thesis, and that problems with the latter make the former implausible as a complete picture of the epistemology of modality. My argument explores the relation between logical modality and metaphysical modality.