Lewis

If two instinct are in conflict, and there is nothing in a creature’s mind except those two instincts, obviously the stronger of the two must win. But at those moments when we are most conscious of the Moral Law, it usually seems to be telling us to side with the weaker of the two impulses. You probably want to be safe much more than you want to help the man who is drowning: but the Moral Law tells you to help him all the same.—Business of Heaven, p. 248, 9.