Offering a fresh approach to one significant aspect of the soteriology of Thomas Aquinas, God's Grace and Human Action brings new scholarship and insights to the issue of merit in Aquinas's theology. Through a careful historical analysis, Joseph P. Wawrykow delineates the precise function of merit in Aquinas's account of salvation. Wawrykow accounts for the changes in Thomas's teaching on merit from the early Scriptum on the Sentences of Peter Lombard to the later Summa theologiae in two ways. First, he demonstrates how the teaching of the Summa theologiae discloses the impact of Thomas's profound encounter with the later writings of Augustine on predestination and grace. Second, Wawrykow notes the implications of Thomas's mature theological judgment that merit is best understood in the context of the plan of divine wisdom. The portrayal of merit in sapiential terms in the Summa permits Thomas to insist that the attainment of salvation through merit testifies not only to the dignity of the human person but even more to the goodness of God.