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.
