Decisions about brain surgery pose existential challenges because they are often decisions about life or death, and sometimes about possible personality changes. Therefore they require rigorous neuroethical consideration. However, we doubt whether metaphysical interpretations of ambiguous statements of patients are useful for deriving ethical and legal conclusions. Particularly, we question the application of psychological theories of personal identity on neuroethical issues for several reasons. First, even the putative “standard view” on personal identity is contentious. Second, diverse accounts of personal identity have been introduced into the neuroethical debate, which are incompatible. Third, the criteria for “diagnosing” the supposed changes in “identity” are ambiguous and indeterminate. Fourth, the metaphysical theories of personal identity imply highly questionable ethical and legal revisions, namely the denial of advance directives, particularly of Ulysses contracts, and, for patients with brain cancer, even therapeutic nihilism.We discuss three examples in which ideas from the personal identity debate in metaphysics are straightforwardly applied to discuss ethical issues of neurosurgery. We discuss revisions of the current medico-legal practice that have been proposed on grounds of psychological theories of personal identity. We argue that the established status quo in law and clinical practice is beneficial to the patients concerned. Furthermore, it is metaphysically neutral, which is an important principle of liberal, democratic, pluralistic societies.We recommend a pragmatic approach: empirical research on personality changes arising from brain disorders or interventions, comprehensive information about risks of personality changes, and advance directives, particularly Ulysses contracts.