[...] In Oneself as Another, the published version of his Gifford Lectures, Ricoeur posits the existence of two separate and opposing strands of individual identity, the idem and the ipse. In Ricoeur's conception of the self, "the narrative constructs the identity of the character"; we use stories about ourselves to make sense of the world and our place in it.
ipse (who one is) is selfhood; idem is sameness, what the self consists of? apparently Infinite Jest specifically mentions the annual Gifford Lecture series, which may be a reference to Ricoeur