Abstract
This book deals with the experience of externality, i.e. an experience, common in schizophrenia, present both in verbal hallucination and in thought insertion. The view defended is that thought insertion is a case of failed agency, experienced by the agent at the personal level as an intelligible thought with which she cannot identify. Such a case in which sense of agency and sense of subjectivity come apart reveals the existence of two dimensions in self-consciousness. Several difficulties of the solution offered are discussed, in connection with the causal-explanatory role of the phenomenological features of the experience and with the view that thinking is a variety of acting.