How we cite our quotes:
"So does every ill that flesh is heir to. What’s true of all the evils in the world is true of plague as well. It helps men to rise above themselves. All the same, when you see the misery it brings, you’d need to be a madman, or a coward, or stone blind, to give in tamely to the plague. (2.7.42)
For Rieux, duty is a matter of common sense. If you’re sane and aware, you either fight the plague or run away like a coward. It’s that simple.
Rieux said that […] if he believed in an all-powerful God he would cease curing the sick and leave that to Him. But no one in the world believed in a God of that sort […]. And this was proved by the fact that no one ever threw himself in Providence completely. (2.7.56)
Rieux explains that he fights the plague not in spite of his atheism, but rather because of it. If God isn’t around, someone has to take a stand in his place.
"Out with it, Tarrou! What on earth prompted you to take a hand in this?"
"I don’t know. My code of morals, perhaps."
"Your code of morals? What code?"
While Rieux cites his atheism as the reason for his taking a stand against the plague, Tarrou simply lists "comprehension." We know this guy is big on awareness, so it seem that to him, as well as to the doctor and to Grand, simply being conscious of the plague leads easily to the logical conclusion that they have to fight it.