In Shakespeare's Hamlet, Polonius advises Laertes, “To thine own self be true.” William James wrote, “Thoughts connected as we feel to be connected are what we mean by personal selves.” Philosophical speculations about the self, its boundaries, our sense of other and where or how the “self” fits into theories of mind have been age-old preoccupations, tied as they are to the unsolved mysteries of consciousness.

Multiple constructs are used by various authors to denote an individual's psychological representation of self. When Sigmund Freud spoke of the self, he called it the soul; however, the word was lost in translation and his three provinces of the soul—“I,” “it,” and “above-I”—became the ego, id, and superego, and what Freud called the structure of the soul became mental ...