"In 'Transcendence of the Ego', Sartre argues that when one turns
inward to examine one's own states one creates a new object, the ego,
that had previously not existed. For Sartre, there is no independent
subject of the classical kind, access to which is secured, as Descartes
believed, by introspection, an inspection of the mind. Consciousness
cannot know itself independent of its relation to things. Far from being
a privileged form of self-knowledge, introspection is for Sartre
largely deceptive."
Robert Bersconi, How to Read Sartre.