Historical and current research on borderline personality disorder reveal certain affinities with schizophrenia spectrum psychopathology. This is also the case for the borderline criteria of "identity disturbance" and "feelings of emptiness," which reflect symptomatology frequently found in schizophrenia and schizotypal personality disorder. Unfortunately, the diagnostic manuals offer limited insight into the nature of these criteria, including possible deviations and similarities with schizophrenia spectrum symptomatology. In this article, we attempt to clarify the concepts of identity disturbance and feelings of emptiness with an emphasis on the criteria's differential diagnostic significance. Drawing on contemporary philosophy, we distinguish between a "narrative" self and a "core" self, suggesting that this distinction may assist differential diagnostic efforts and contribute to mark the psychopathological boundaries of these disorders.