Full Idea
One cannot rule out the metaphysical hypothesis that my Ego is not composed of elements that have existed in reality (ten years or one second ago), but is merely constituted by false memories.
Gist of Idea
It is theoretically possible that the Ego consists entirely of false memories
Source
Jean-Paul Sartre (Transcendence of the Ego [1937], II (D))
Book Reference
Sartre,Jean-Paul: 'The Transcendence of the Ego' [Routledge 2004], p.31
A Reaction
(He mentions the evil demon as a source). The problem that false memories (such as George IV 'remembering' he was at Waterloo, when he wasn't) is well known. But this raises the possibility of all memories being false, yet constituting the person.