The whole attitude of existentialism is perhaps best seen in the most-popular existentialist novel of the twentieth century, Albert Camus' short book, The Stranger, which I'll summarize in hopes of giving the reader a good “feel” for existentialism.
The hero of the story, a man named Mersault, is supposed to be the quintessential existentialist man. Nothing holds any meaning for him; he's indifferent to things most people value–family, love, social conventions, money, career. He goes through life with little thought of others; primarily because he gives little thought to himself. He just goes about and lets the events of life bounce off him, indifferent to any aspirations for himself, puzzled by aspirations in other people. When his mistress, for instance, asks if he loves her, he describes his response as follows: “I answered . . . that it didn't mean anything, but that I probably didn't love her.” When his mother dies, he obliges the social conventions–to sit at casket vigil for a day–but feels no remorse; he doesn't feel any annoyance at the vigil, either; he simply doesn't care either way.
This indifference gets Mersault sentenced to death. He becomes friends with a pimp named Raymond, who at one point beats his girlfriend, an Arab woman. The woman's brothers later attack Raymond in revenge while Mersault is with him, but are beaten back. Later, Raymond and Mersault see the Arabs again, and Raymond proposes to shoot them in cold blood. Mersault advises against it and convinces Raymond to give the revolver to him. Later Mersault is walking alone on the beach and, on the verge of heat stroke, sees one of the Arabs again. In order to get out of the sun, he walks towards the shade, which is in the Arab's direction; the Arab pulls a knife, and Mersault, in self-defense, shoots him.
At his subsequent trial, Mersault is convicted of murder. One of the primary pieces of evidence: His callousness at his mother's funeral. He must, the prosecutor convinces the jury, be a monster. He is sentenced to death. While awaiting his execution, the prison chaplain visits him and urges him to reconcile himself with Christ. Mersault, unsurprisingly, is indifferent to anything like religion or the after-life and doesn't see any sense in the chaplain's urgings. The minister doesn't relent until Mersault blows up at him, crying out that none of it makes any difference; all men are equally worthy; all men live under a sentence of death. It doesn't matter that his mother died; it doesn't matter if his girlfriend is now kissing another man. It all doesn't matter. In short, Mersault says the universe has no meaning in it, so how can all the things that people find so important matter?
Prior to his emotional explosion, Mersault was disturbed at his pending death. After it, he was calm and welcomed it. Camus made it clear that Mersault, always the stranger, had finally become conscious of his existentialism, of why he was so indifferent to everything. As a result, Mersault could greet death, too, with indifference–and equanimity.
Mersault is the poster boy of twentieth-century existentialism.