This article draws attention to Thomas Aquinas' under-appreciated development of the doctrine of the atonement. I argue that Thomas' pursuit of the ‘fittingness’ of the passion yields an exceptional grasp of the multiplicity of effects accomplished by Christ's death. To defend this thesis, I explore the methodology underlying Thomas' approach to the atonement, contrasting it with that of Anselm. I then follow the implications of Thomas' methodology in his stance toward the diverse atonement theories of his day. In conclusion, I briefly note the significance of Thomas' method and conclusions for contemporary debates concerning the efficacy of Christ's passion.