Meursault, in Camus' short novel, The Stranger, is a very unusual man. His life reflects a inordinate lack of concern, to the positive or negative, about almost anything. He enjoys the repetitive nature of his existence, sees no need to change anything, will go along with what others want in order to avoid any crisis or discomfort, and passes from one day to the next without truly becoming passionate or caring about anything or anyone in his life.
When his mother dies and he goes to her funeral, Meursault shows no grief whatsoever.
When his boss offers him a chance to open a new office in Paris, he really doesn't care that this would be a fine opportunity for him.
...he wanted to know if I’d like a post there.
“You’re a young man,” he said, “and I’m pretty sure you’d enjoy living in Paris. And, of course, you could travel about France for some months in the year.”
I told him I was quite prepared to go; but really I didn’t care much one way or the other.
Marie came that evening and asked me if I’d marry her. I said I didn’t mind; if she was keen on it, we’d get married.
Then she asked me again if I loved her. I replied, much as before, that her question meant nothing or next to nothing—but I supposed I didn’t.
Then she remarked that marriage was a serious matter. To which I answered: “No.”
She kept silent after that, staring at me in a curious way. Then she asked: “Suppose another girl had asked you to marry her—I mean, a girl you liked in the same way as you like me—would you have said ‘Yes’ to her, too?”
It is easy to see that Meursault will go along with whatever Marie suggests, but he does not take marriage seriously, and would have said yes to anyone girl who had asked if he liked her as much as he liked her. And he cannot tell her he loves her because he does not. That would be a passionate response, and he seems to have no emotional responses other than to get annoyed occasionally.
When Raymond gets into trouble with the police for beating his girlfriend, he asks Meursault to be his witness about her infidelity, and Meursault readily agrees, though he has no idea if she was unfaithful or not. He simply agrees to do so, and when he goes to the police station to give a statement, no one checks it out.
When Meursault, through a combination of illness and seeming confusion, kills the Arab, he admits that he is sad that the man is dead, but shows no remorse for his part in it.
He feels equally disinterested in whether there is a God, even though the magistrate, and later the chaplain speak to him about it with great passion. He doesn't see the need to believe in God. It makes no difference to him.
This lack of passion, of caring, of being involved in the world around him and paying more attention is what gets him into trouble. By the time the court case comes around, there are very few who can stand up for him to attest to his sincere concern for others, his willingness to be a dedicated friend, to be a devoted and caring son, or a man of God. His routine of repeating each day without dedication to anything but maintaining the status quo paints him as a self-centered, uncaring, Godless man with criminal tendencies, and he is sentenced to death.