In recent years Luther’s teaching on the atonement has been a subject of strong dispute. Some (mostly the Swedish interpreters) have stressed the ideas of “conflict” and “victory” in Luther’s discussions of atonement, arguing for a discontinuity between the Reformer’s own thinking and the “substitutionary” theory of later Protestant orthodoxy. Others have insisted that at this point Luther’s teaching differs in no essentials from that of his successors. One is well advised to tread carefully on entering the field of controversy; nevertheless, I make bold to submit that the interpretation of atonement in both Luther and Calvin can be understood as turning on the central and pivotal conception of a “happy exchange,” in which the believer’s sins are laid upon Christ and Christ’s own innocence is communicated to the believer. From this center, we may say, the Reformers’ thinking moves outwards to the various other soteriological concepts, including the two about which modern opinion is chiefly divided, namely, “victory” and “substitution.” First and foremost, the Christian is one who has been united with Christ so intimately that an exchange of qualities has somehow taken place.
Of course, this understanding of Luther’s thought would not settle present-day controversies, for it is not incompatible with either of the two main rival theories, nor even with a combination of both. Neither is it incompatible with Calvin’s threefold scheme of “Prophet, Priest, and King” (a scheme of which, in any case, he makes very little use), since Christ does not exercise these offices in any “private capacity,” but rather communicates their benefits to believers. Perhaps we may say that the notion of “exchange” belongs to the presuppositions of atonement, as the Reformers understood it, whilst the detailed outworking of the doctrine demands the use of further categories.
That the notion is indeed fundamental to the Reformers’ thinking could be demonstrated by many passages from the works of both.
Luther speaks explicitly of this “happy exchange” (fröhlich Wechsel) in the German version of the Treatise on Christian Liberty. The soul and Christ are united like bride and bridegroom. They become one flesh, and everything they possess is shared in common. “What Christ has is the property of the believing soul, what the soul has becomes the property of Christ.” A similar passage occurs in the Larger Commentary on Galatians (though worded differently in Rörer’s MS.): “So, making a happy exchange with us (feliciter commutans nobiscum) he [Christ] took upon him our sinful person, and gave us his own innocent and victorious person.” These passages can readily be matched in Calvin’s Institutes: “Who could do this [i.e., win salvation for men], unless the Son of God should become also the Son of Man, and so receive what is ours as to transfer to us what is his?” And again: “He was not unwilling to take upon him what was properly ours, that he might in turn (vicissim) extend to us what was properly his.” The same pattern of thought recurs in both the Reformers when they speak of the Lord’s Supper; as, for instance, in Luther’s Treatise on the Blessed Sacrament, and the fourth book of Calvin’s Institutes. What exactly it is that is “exchanged” is made perfectly clear in each of these passages: namely, Christ’s righteousness is exchanged for the believer’s sin.
–Brian A. Gerrish