On July 18, 1957, Lewis writes to Joan Lancaster:
But of course you are quite right if you mean that giving up fun for no reason except that you think it’s ‘good’ to give it up, is all nonsense. Don’t the ordinary old rules about telling the truth and doing as you’d be done by tell one pretty well which kinds of fun one may have and which not? But provided the thing is in itself right, the more one likes it and the less one has to ‘try to be good’, the better. A perfect man wd. never act from a sense of duty; he’d always want the right thing more than the wrong one. Duty is only a substitute for love (of God and of other people) – like a crutch, which is a substitute for a leg. Most of us need the crutch at times: but of course it’s idiotic to use the crutch when our own legs (our own loves, tastes, habits etc) can do the journey on their own!
I’d not thought of the distinction Lewis makes between duty and love prior to reading this letter. As a matter of fact I’ve always ranked duty high on my list of virtues – a sense of duty has been important to me. Is Lewis equating duty with obedience to the Law? That is, he is in effect saying, “If we need to conform our actions to an external Law in order to do the right thing then it is better to do that than not to do it; however, as we are transformed by grace into the image and character of Christ then we no longer need the scaffolding of the Law to motivate us to right behavior, for our internal character will naturally rejoice in right behavior – we will love God and others”.
I don’t know if this is what Lewis means or not, I’m thinking out loud on paper, so to speak/write. My take on the performance of duty has been that grace empowers me to fulfill my duty – I see my duty and I do it; there may even be a sense in which we can say, “I love fulfilling my duty. I have a love of duty.” But again, I’m thinking out loud.
A problem with equating duty with Law is that Law cannot produce obedience; it produces death and condemnation (2 Corinthians 3:5-11). So I don’t think Law and duty are the same thing because Law can only produce failed attempts at doing what is right, and I don’t see duty in that same light. Anyway, I thought this excerpt worth posting in the hope it might stimulate our thinking.