Marie Cordona serves as a foil for Meursault throughout The Stranger. Marie is filled with joy: she laughs frequently, feels strongly, and says she loves and wants to marry Meursault. Meursault, on the other hand, feels little, and while he is attracted to Marie and agrees to marry her, he views her as rather interchangeable—that is, she suits him just as well as any other woman who likes him would. While Marie has liked Meursault ever since working as a secretary at his workplace, Meursault himself does not actively choose Marie but simply reciprocates her interest in a more passive manner.
Marie also cares about and prioritizes other people’s emotions in a way Meursault does not. When she visits Meursault in jail, she puts on a fake smile to make him feel better. This act, however small, reveals a care and compassion for other people's feelings that Meursault himself does not demonstrate. Throughout the novella, Marie serves as a stand-in for a person with a more normative emotional way of moving through the world; someone who, in other words, cares both about life and about other people. Juxtaposed against Meursault, she comes across as warm, joyous, and full of life, whereas Meursault comes across as melancholic, apathetic, and often cruel
Despite initially appearing to despise his dog, dragging him along on walks and beating him frequently, Salamano ironically becomes distraught when the dog runs away:
He was looking down at the tips of his shoes and his scabby hands were trembling. Without looking up at me he asked, “They’re not going to take him away from me, are they, Monsieur Meursault? They’ll give him back to me. Otherwise, what’s going to happen to me?” I told him that the pound kept dogs for three days so that their owners could come and claim them and that after that they did with them as they saw fit. [...] from the peculiar little noise coming through the partition, I realized he was crying. For some reason I thought of Maman.
The situation is ironic in that the old man drove the dog away by beating it, only to then weep over its disappearance. The notion that people don't know what they have until it's gone comes up again and again throughout The Stranger, from Raymond and his mistress to Meursault and his introspection while on death row. It also shows the complications and contradictions that make up who people are: one page earlier, Salamano proclaims “pay money for that bastard—ha! He can damn well die!” before later being brought to tears over the dog. Salamano feels incredibly negatively, and incredibly positively, toward his dog, caught up in the contradictions of feeling. The inability to understand life is, for Camus, foundational to the absurd, and it is demonstrated in these unintelligible contradictions.
Salamano, in demonstrating a deep emotional attachment to his dog, also serves as a foil for Meursault, whose apathy is his defining characteristic. While Meursault "for some reason" thinks of Maman after hearing Salamano cry, he doesn't connect that crying to his own emotions. Meursault, in other words, does not demonstrate the same emotional range of other characters in the novella. If Meursault thinks of Maman because he feels similarly to Salamno, he isn't able to admit that to himself or to the reader.