I've a friend who's a good Catholic. Last week he expressed curiosity about how Baptists and more generally Protestants stay on the straight-and-narrow. I failed to give a good answer and this is an attempt to put my understanding into words. Keep in mind that I'm not any ecclesiastical authority and whatever I say should be checked against scripture. Don't take my word for any of this. Check it out for yourself.
First off, I'm Reformed enough to think that God saves sinners. Sinners don't save themselves or accept any power-assist or make any leveraged deals for grace. My state outside grace is like a dead man completely incapable of doing anything acceptable to God. Some disagree, thinking there may be some unfallen spark of desire for God that must be fanned into flame. But I don't.
However, I believe that when a human presents to another human the good news of the gospel and calls upon a sinner (we're all sinners by birth) to repent & believe, God chooses to add his effectual call of the Holy Spirit to the message. Quite frankly, I believe every Christian starts his Christianity with a miracle of resurrection in a spiritual sense. Before that, everyone is disinterested in the God that Is and is anxious to either get away or substitute something he finds more acceptable.
When God goes "zot" like this, the sinner brings nothing to the transaction but his sin, his desire/promise to not-sin, and his belief that God will forgive him. Where I show I'm uber-Reformed is that I think the expressions of belief, the repentence, and the faith are all RESULTS of grace, not CAUSES of grace.
So, at this point my Catholic friend asks, "So, why do good after this?"
I was reminded of this question last Sunday. The preacher spoke of the merit of Christ and the imputation of his righteousness, his merit to the believer in exchange for the believer's sins. And after that we live in the power of Christ to do good.
I nudged my wife and whispered, "why?"
The answer I didn't give my Catholic friend, but that I did give my wife is "gratitude."
Gratitude is the only reason any Christian should ever do any good thing. Keep in mind two things, we've asked God to save us from our sins, which means we want to be rid of them. Second, God provides this grace free of charge and I think God is offended by any attempt to pay for it via religious activities. So, I've got this debt of gratitude that is infinite in extent. I'm not obligated to pay it off, but I think it is only fitting for a Christian to keep this in mind. When there's some little sacrifice I'm called upon to do, I compare it with the sacrifice of Christ on my behalf. It's only fitting to do what I can as an expression of gratitude.
I think that as long as I realize that nothing I'm doing is getting me to heaven, or keeping me in the boat, but that everything's in God's hands, there is no room for vanity. When Jesus spoke of the Pharisee and he Tax Collector and how they prayed, the Pharisee seems altogether too satisfied with his spiritual state. He's grateful for not being like the guy next to him, but the Christian's gratitude must run much deeper. We're all sinners, and just because I'm a nice guy right now, that doesn't mean all the bad things i did in the past are inoperative. There's more than the moral delta between Pharisee & Publican, there's the delta between absolute perfection as lived by Jesus and my own sinful state. I've got to remind myself how much I've been given to properly assess a fitting extent of gratitude toward Christ.
Why be good? Because it's the least I can do.