Research on personal identity often relies on imaginary cases and tends to theorise about our nature from the first-person perspective. In this paper I argue that a problem arises when we combine the two methods and assess imaginary cases from the first-person perspective. The problem is that the link between de se imagination and modality is broken. De se imagination regularly gives rise to de se modal illusions. De se modal illusions come in two varieties: there are de se illusions (...) of possibility and de se illusions of impossibility. I present a systematic account of the two types of illusion. I further make the case that the proposed account is compatible with maintaining a general link between imaginability and possibility. I apply the account to two concrete cases and use it to undercut the motivation behind a central theory of personal ontology, Dualism, and a central account of personal persistence, Lockeanism. (shrink)