“Lord, Have Mercy on Me, a Sinner”: Aquinas on Grace, Impetration, and Justification

This article explores St. Thomas Aquinas's doctrine of grace for the way in which it heals and moves the sinner towards justification. It exposits Thomas's use of the language of “impetration” to express a causal yet non‐meritorious role for human action, and it applies this conception to the free will's movement in justification. It argues that Thomas understands the prayer of a sinner to illumine the way in which God's infallible and predestinating will unfolds through human actors without destroying their contingent nature. To that end, it first exposits critical points in Thomas's doctrine of grace, including the notions of habitual grace and auxilium, intact and fallen human nature, and operative and cooperative grace. It then introduces the language of impetration for the way in which it elucidates a valuable role for human action in justification. It concludes that impetration illustrates the on‐going perfection of nature in such a way that God's grace draws human beings into the causal sequence of divine providence. The sinner's impetration captures the indispensable movement of the free will while recognizing that, in its appeal to divine mercy, it has already been graced by God and cannot earn the gift of justification.