This paper first explains the difference between conceivability and metaphysical possibility from the perspective of possible worlds. Then, it introduces Saul Kripke’s view on the metaphysical necessity of identity, contributing to a premise in Descartes’ Conceivability Argument. Next, this paper interprets the Conceivability Argument. Then, this paper argues that even if “two things are distinct” is conceivable, we cannot conclude that their distinction is metaphysically possible, so conceivability does not entail metaphysical possibility. Thus, the Conceivability Argument is problematic. This paper also responds to a potential objection that, given humans have clear and distinct ideas, conceivability will entail metaphysical possibility.