In Selves in Doubt, Eli Hirsch focuses on the importance of the first-person perspective to a normal human level of rational thought and behavior. Hirsch argues that an "I-blind" being—one who lacks the capacity to employ the first-person pronoun—could not be fully rational; nor could they acquire normal knowledge of physical reality.The meaning of the first-person pronoun is shown to have a particular bearing on the anomalous context of split-brain patients and generalizations of that context. Hirsch critiques Parfit's suggestion that a better language might eliminate or revise the concept of personal identity and the use of the first-person pronoun, on the grounds that the first-person perspective must remain as it is because the capacity to employ the first-person pronoun is a necessary condition for a language to be suitable for rational beings. Hirsch also contends that, contrary to Lewis and Sider, it may be difficult to find any other necessary condition for a language to be suitable for rational beings.A bold claim defended later in the book is that it is metaphysically impossible to be sane while doubting the reality of other selves. This claim leads to a discussion of skepticism, and the final chapter consists in reflections on how facing skepticism relates to facing death.