What mattered most of all was my deep-seated hatred of authority, my monstrous individualism, my lawlessness.Becoming C.S. Lewis p. 185
Lewis certainly pegs the foundation of his poor behavior. When we are our own gods we despise all other gods, i.e. authority, and are grotesquely individual. My honor matters; my glory matters; my opinion matters.
That is not to say that no foundation other than Jesus means no good can come. Certainly the materialist can do a good deed—but why is he doing it? There is something in it for him. However altruistic in appearance, the reality is the hope of something accruing to one’s own account. And that is monstrous. We use our good deeds to ultimately point to self. I am the motivation, and I am the law unto myself.
But let’s also not assume it’s so insidious. I certainly, in the moment, might not be aware, especially if the action is culturally acceptable. Going along with what the world says is good can hardly be a vice can it?