Aristotle's Moral Ballast in Screwtape Letters

Aristotle had this idea that there was sort of a center of gravity to your moral nature. Lewis develops this, I think, in Screwtape Letters,. Every time you make a good decision, your moral center of gravity kind of tilts upward a little bit. And then it's easier to make a good decisions next time. But every time you made a bad decision or partake in a dictivact, your center of gravity goes downwards. It's harder the next time to resist that temptation because you don't have the kind of moral ballast that you might have had.