I see genuine contentment in your gait and mien, your eye and face, when you are helping me and pleasing me – working for me, and with me, in, as you characteristically say, “all that is right:” for if I bid you do what you thought wrong, there would be no light-footed running, no neat-handed alacrity, no lively glance and animated complexion. My friend would then turn to me, quiet and pale, and would say, “No, sir; that is impossible: I cannot do it, because it is wrong;” and would become immutable as a fixed star. Well, you too have power over me, and may injure me: yet I dare not show you where I am vulnerable, lest, faithful and friendly as you are, you should transfix me at once.
– Charlotte Bronte
Jane Eyre, Chapter 20. Rochester appears to acknowledge that Jane would refuse to do anything he asked her to do that was morally wrong. Yet later he asks her to do just that, when he wants her to be his mistress!