From Steven Paulson’s tremendous overview of the roots of the Lutheran faith, Lutheran Theology, in which he talks about the radicality of Luther’s understanding of “faith alone,” and its perpetual endangerment before the human yearning to earn.

The key problem with mixing up grace and some capacity of the soul…is that we fail to understand how the Gospel justifies by faith alone…Possession (of righteousness) nullified utterly by law in death, and does not return when we are made alive again. Instead, what faith grasps is a promise, but a promise is not legal property; it is a word that engenders hope because its veracity depends upon another. Our justification happens by a Christ who is not simply a new Moses, but a Christ who himself went through death for our trespasses, and was raised for our justification. So sinners like Abraham will be made exactly like Christ–put to death and only then raised from the dead–not by any process of moral improvement that seeks in the end to be just in itself.

The righteousness is Christ’s, and always will be; sinners never possess it as a piece of distributed justice by which we can stand before God’s eternal wrath and be exonerated. Therefore, justification is not a single event upon which sanctification is then built. We return again and again to justification by Christ’s favor, and therefore there is no salvation without a preacher–whom we need daily.

…There is no neutral, natural quality of the soul waiting to be taught how to make the right choices, or how to orient desire to its proper goal. God’s wrath is total, and unrelenting, and no one escapes. There is no neutral territory for this imaginary “faith” as a virtue or act of humans. For the Lutherans, Christ is the only righteousness, and his righteousness is preached by a word of promise that says, “Your sins are forgiven.” How? “On my account (proper Christum).” Hearing this word makes faith, and this faith is reckoned or imputed as righteous, though there is no righteousness there by any measure of law–including the presence of love as caritas. To call divine imputation (as a declared word) a “fiction” is to say that the only truth in life is law, and in turn that is to blaspheme the Gospel–to make Christ into a Moses and to make of Abraham the father by circumcision, not by faith (128-129).