The Stranger focuses on one man’s isolation from society, from friends, from his lover, from human emotion, and eventually from normal logic. This isolation is self-prescribed; the main character isn’t exiled by any means – he separates himself. Of course, at first he doesn’t view this as a choice at all; isolation is simply the path of least resistance, the series of activities that requires the least activity and effort. By the end of the novel, the narrator realizes that he has the ability to choose; that if he wants, he can wish for a large crowd of people, he can desire to be less alone. Or he can stay as he is. But he is conscious of his own ability to decide.
Content as a spectator in life, Meursault can be considered solipsistic – his own irrational response to an irrational world.
The event most characteristic of Meursault’s detachment to this world is his refusal to see his mother one last time.