"Each subject uses a concept of self (or ‘I’) to reflect on and store information about herself. Possessing this concept, and thus being able of explicit self-representation, is arguably what makes a creature a fully-fledged self, or subject. The fundamental hypothesis of the proposal is that this I-concept is interestingly akin to phenomenal concepts (i.e. those concepts, like “red”, “shrill” or ""painful"" we use to describe how our experiences feel to us).The key research questions that this new theory is designed to answer are: (1) What is the semantics of the self-concept, i.e. what representational mechanism do we deploy to refer to ourselves through it? (2) How does the proposed semantics help solve some open philosophical issues concerning the self-concept? These include issues (2a) in epistemology; (2b) in the metaphysics of persons and moral philosophy. (3) What further implications does the proposed semantics have for issues raised by the self-concept in neighbouring disciplines, such as cognitive psychology, neuropsychology and psychopathology?(1) I propose a new semantics for the I-concept, conceived for the first time as a special type of phenomenal concept; this semantics is inspired by that of a class of linguistic expressions called indexicals. (2a) On this basis, I transpose what is known about phenomenal knowledge to the case of self-knowledge. (2b) The theory also suggests a new account of what grounds the special value we ascribe to persons as such, and why subjects care about their own survival through time. (3) I argue that psychiatric troubles (e.g. schizophrenia, Cotard syndrome) affecting personal identity and the mastery of ‘I’ come from a dysfunction of the phenomenal “sense of self” I posit to explain how we can come to acquire a self-concept."