For Luther, the Christian life is a gospel-grounded, gospel-built, gospel-magnifying life that exhibits the free and sovereign grace of God and is lived out in gratitude to the Savior who died for us, yoked to Him in cross-bearing until death is swallowed up in victory and faith becomes sight.
What do the sovereignty of God, salvation by grace, justification by faith, and new life in union with Christ mean for the living of the Christian life? For Martin Luther, they carry four implications:
The first implication is the knowledge that the Christian believer is simul iustus et peccator, at one and the same time justified and yet a sinner. This principle, to which Luther may have been stimulated by John Tauler’s Theologia Germanica, was a hugely stabilizing principle: in and of myself, all I see is a sinner; but when I see myself in Christ, I see a man counted righteous with His perfect righteousness. Such a man is therefore able to stand before God as righteous as Jesus Christ—because he is righteous only in the righteousness that is Christ’s. Here we stand secure.
The second implication is the discovery that God has become our Father in Christ. We are accepted. One of the most beautiful accounts found in Luther’s Table Talk was, perhaps significantly, recorded by the somewhat melancholic, yet much loved, John Schlaginhaufen:
God must be much friendlier to me and speak to me in friendlier fashion than my Katy to little Martin. Neither Katy nor I could intentionally gouge out the eye or tear off the head of our child. Nor Could God. God must have patience with us. He has given evidence of it, and therefore he sent his Son into our flesh in order that we may look to him for the best.
Third, Luther emphasizes that life in Christ is necessarily life under the cross. If we are united to Christ, our lives will be patterned after His. The way for both the true church and the true Christian is not via the theology of glory (theologia gloriae) but via the theology of the cross (theologia crucis). This impacts us inwardly as we die to self and outwardly as we share in the sufferings of the church. The medieval theology of glory must be overcome by the theology of the cross. For all their differences in understanding the precise nature of the sacraments, Luther and Calvin are at one here. If we are united with Christ in His death and resurrection, and marked out thus by our baptism (as Paul teaches in Rom. 6:1–14), then the whole of the Christian life will be a cross-bearing:
The Cross of Christ doth not signify that piece of wood which Christ did bear upon his shoulders, and to the which he was afterwards nailed, but generally it signifieth all the afflictions of the faithful, whose sufferings are Christ’s sufferings, 2 Cor. i.5: “The sufferings of Christ abound in us”; again: “Now rejoice I in my sufferings for you, and fulfil the rest of the afflictions of Christin my flesh, for his body’s sake, which is the Church”. (Col. i.24). The Cross of Christ therefore generally signifieth all the afflictions of the Church which it suffereth for Christ.
The believer’s union with Christ in His death and resurrection and its outworking in daily experience thus became, for Luther, the spectacle lenses through which the Christian learns to view every experience in life. This—the theologia crucis—is what brings everything into sharper focus and enables us to make sense of the ups and downs of the Christian life:
It is profitable for us to know these things, lest we should be swallowed up with sorrow or fall to despair when we see that our adversaries do cruelly persecute, excommunicate and kill us. But let us think with ourselves, after the example of Paul that we must glory in the cross which we bear, not for our sins, but for Christ’s sake. If we consider only in ourselves the sufferings which we endure, they are not only grievous but intolerable; but when we may say: “Thy sufferings (O Christ) abound in us”; or, as it is said in Psalm xliv: “For thy sake we are killed all the day,” then these sufferings are not only easy, but also sweet, according to this saying: “My burden is easy, and my yoke is sweet” (Matt. xi.30).