Plantinga’s conception of possible worlds is problematic in one sense: it relies on the prior idea of modality. His strategy for resolving the puzzle of transworld identity is significant in the metaphysical sense but fruitless in the epistemological sense because world-indexed properties cannot be used as effectively in epistemic practice as their counterparts, i.e., space- and time-indexed properties. His isolation of transworld identification from transworld identity is unconvincing. This paper argues that the intelligibility of modal discourse and reference is the essence of transworld identity. It is also proved that transworld identification is the epistemic ground of such intelligibility. Hence, the transworld identification problem is the epistemological foundation of the transworld identity problem, and there must be a comprehensive answer to the former.