So the outward turn of attention in Luther’s doctrine of justification, based on a kind of sacramental externalism and summed up in the phrase “alien righteousness,” must not be confused with the very different externalism of the purely forensic doctrines of justification that predominate in Protestantism, according to which the righteousness of faith makes no inward change in us but only gets Christ’s merits imputed to us. On the contrary, for Luther the alien righteousness of faith is the deepest thing in me: it is Christ dwelling in my heart and conscience as a bridegroom in the bridal chamber, so that “Christ and my conscience … become one body” with the result that I am an entirely different person. I am reborn as that good tree which can bear good fruit, a person who can by faith actually do good works, which make up what Luther calls my own “proper” righteousness. This latter is not the inward and alien righteousness in the depth of my heart, by which I am justified before God, but the external works of righteousness I do for the sake of my body or my neighbor.
We must get used to such apparent reversals in Luther: my own proper righteousness is merely external to me, a thing of the body, while an alien righteousness, found outside me, is what is deepest in my soul. The only way such reversals make sense is if Luther is thinking sacramentally, in terms of an inward gift that I apprehend outside myself.
Read the extended excerpt on the Pontificator’s blog.