It is worth noting the influence of William Ockham and the via moderna in setting the stage for Calvin’s articulation of justification—most notably the medieval distinction between the “two powers” of God. The theologians of the via moderna made full use of the medieval distinction between the potentia dei absoluta and the potentia dei ordinate, God’s “absolute” and “ordained” power, respectively. The potentia dei absoluta referred to God’s utter freedom in choosing whatever he desired (bound only by his own nature and the law of non-contradiction). The potentia dei absoluta was emphasized in an attempt to protect God’s free grace in justification. God need not have made the world, chosen to redeem it once it fell, or indeed, have done anything that actually occurred in human history. God is not bound by human justice, and there is nothing within humanity—even the perfect humanity of Christ—that can of necessity compel God to act graciously. Within the framework of the potentia dei absoluta, God is not bound to honor any created thing. His complete otherness, his utter transcendence, makes it impossible for any created thing to lay claim on him.
The capriciousness of God de potentia absoluta was countered by the potentia dei ordinate—that which God had chosen to actualize in human history. God, in his grace, had freely chosen to provide humanity with a way of salvation via a pactum, a graciously appointed covenant. In as much as the pactum was established by God and ratified with an oath, God—who cannot lie—was bound to honor it. Within the framework of this pactum, God freely agreed to grant the grace of justification to the one who “does all that is within him”—facere quod en se est—to love God with a pure act of love. (Notably this act of pure love could be performed quite apart from any divine enablement or infusion of grace. Augustine, of course, would have been horrified). Once one has done all that was within him, he received the divine acceptation—his deed was accepted by God as meeting the pre-established demands of the pactum—and was subsequently granted the grace of justification. Thus the focal point of justification in the via moderna moved away from ontology to status. The question was no longer, “How do I become ontologically righteous?” (per Augustine) but rather, “How do I secure the divine acceptation? (per Ockham).
Calvin does not speak in the language of the medieval synthesis; he deplores the medieval distinction between the “two powers” of God, and undoubtedly would have preferred Ockham turn his razor on himself. I’ll leave it to the specialists in medieval theology to charter a more direct path between Calvin and the via moderna, but it is apparent that Calvin’s employment of forensic language and its subsequent emphasis on legal status fits neatly within the framework already established by the via moderna. Calvin’s doctrine of justification, like the via moderna, is concerned with acceptance—for Calvin, specifically legal acceptance.
Recognizing the shift from ontology to status goes a long way towards explaining why Calvin and Augustine have substantive differences in their respective doctrines of justification, yet utilize similar semantics. Though both Augustine and Calvin affirmed the formula “justification by grace through faith apart from works,” they did not use the expression with the same meaning. Augustine saw justification as identical to spiritual regeneration; to be justified was to be born again—to be made ontologically righteous. Calvin however, was interested in justification as it related to legal acceptance; to be justified was to be made legally righteous.
Adding to the difficulty in distinguishing between Calvin and Augustine, is the eschatological focus of justification within their respective systems. For Augustine, justification—being born again—is not primarily about how to merit eternal life, but rather about how to become ontologically righteous. For Augustine, the righteousness secured in justification enables one to merit eternal life through subsequent good deeds. Consequently, Augustine’s merit theology adds a dimension to his thought that is absent in Calvin. Calvin, for his part, views justification itself (i.e., free acceptance) as the doctrine that addresses the question of eternal life. For Calvin, to be justified ultimately means to be made fit for eternal life. Calvin asks more from his doctrine of justification than does Augustine.