Another difference [between Modern Theology and Mercersburg Theology] is in their central iea. Modern theology makes the atonement or death of Christ, Mercersburg the person of Chirst or the incarnation, its central idea. The importance of this difference can be seen in the fact, for instance, that the atonement itself, or justification by faith, cannot be maintained successfully by adopting the former. According to it, the atonement is made to rest primarily on what Christ has done, not on what he is. It apprehends Christ as a mere individual, God and man in one person, it is true, but yet as a mere individual. Mercersburg theology apprehends Christ as the embodiment of the universal life of humanity, the second Adam or federal head of the race’ and his obedience and death receive their atoning merits from this fact. When he was nailed to the cross, more than a mere individual was nailed to the cross– humanity itself– was nailed to the cross; consequently whatever merits attach to his suffering and death belong to the race as a whole– not to one individual simply– nor to a limited number of individuals– nor to all individuals numerically considered– but to humanity as a whole (which is something more, and deeper, and broader and more universal, than any number of mere individuals),– subject to appropriation by all who claim them for their individual wants.If Christ had been a mere individual, one among many, no such universal atonement nor even a limited atonement, could have been possible. The merits of his death could apply no farther than to himself, and the idea of the atonement, as available for others, falls to the ground. The idea of one individual dying for the crimes of another individual, does not satisfy the demands of justice. The doctrine of the atonement must be apprehended in a profounder sense than this comes to, and this depends on a proper conception of the person of Christ.
Samuel Miller, A Treatise on Mercersburg Theology; or, Mercersburg and Modern Theology Compared pg. 19-21
