Deadly Sin
Via On Being a Theologian of the Cross pp. 36-38
Thesis 5. The works of men are thus not mortal sins (we speak of works that are apparently good), as though they were crimes.
Thesis 6. The works of God (we speak of those that he does through man) are thus not merits, as though they were sinless.
Luther here points to a deepening of the concept of mortal or deadly sin. What makes a sin “mortal” or “deadly”? Not just that it is a violation of law so flagrant that everyone would condemn it. We would quite readily recognize and perhaps even confess to that. A deadly sin is one that actually separates and seals us off from God. That occurs when the apparent goodness of our works seduces us into putting our trust in them, that is, it occurs when the very goodness of the work is such that it dissuades us from confessing. We are in reality then, not just in theory, sealed off from grace. As we put it earlier, the works of the law are used as a defense against the very unconditionality of the gift of grace. A human work, no matter how good, is deadly sin because it in actual fact entices us away from “naked trust in the mercy of God” to a trust in self. The symptoms of such deadly sin can be detected, therefore, in the very midst of our piety when complaint is unthinkingly launched against the “cheapness” of grace, or the fear that it leads too readily to moral laxity, permissiveness, and so forth. These are words that bespeak trust in the apparent goodness of human works and distrust in the power of divine grace. Thus they cut the sinner off from God — deadly sin! In actual fact we fall very easily into calling evil good and good evil!
This means, consequently, that we must be very careful about how we regard even those works God does in us. Deadly sin lurks in the most pious places. This is the concern of thesis 6. Even those works that God does in us are not accounted as “eternal merits” because they are supposedly sinless. None of our works, not even those done in us by God are sinless. Luther’s proof is a discussion of Ecclesiastes 7:20, “Surely there is not a righteous man on earth who does good and never sins.” Some would want to interpret the passage to say that a righteous man may indeed sin, but not when he is doing good. Luther dismisses that interpretation by claiming that had the Holy Spirit meant that it would have been said much simpler: “There is not a righteous man on earth who does not sin.” But it is not the habit of the Holy Spirit to babble such platitudes. The passage should be taken to mean therefore that even the good deeds done in the righteous by God are not sinless. That is to say, the righteous are simultaneously just and sinners (simul iustus et peccator), a fundamental tenet of Luther’s doctrine of sin and grace. Being theologians of the cross means also looking at ourselves through suffering and the cross and being able to “say what a thing is,” to confess the truth. We look to God and not to ourselves — not even to those works that God does in us.