The One Christ: St. Augustine's Theology of Deification
130 The Son's Descent claim that in Christ men and women can participate in God. He can admit on a couple of occasions that the human person participates in the divine nature.105 Neverthless, such claims are admittedly limited in Augustine's works as a whole. In fact, as it stands, the only instances of his citing 2 Pet. 1:4 appear when he reports how it has been co-opted by the Pelagians.
As Augustine understood Pelagius and his followers, everything the human person required for perfection was already found within. Such anthropological assurance helps to indicate why neither 2 Pet. 1:4 nor perhaps a more sustained discussion on "partaking of the divine nature" finds an explicit place in Augustine's grammar of divine union. It also helps to explain why he never uses 2 Pet. 1:4 as a way of describing deification. We shall pass over the accuracy of Augustine's understanding of the Pelagian system, but what is clear is that he associates the formula "partakers of the divine nature" with their perceived project of casting the human person as a part of the divine [pars Dei] without sin or fault. Augustine reports that Caelestius "cited the testimony from the apostle Peter that we are sharers in the divine nature (2 Pet. 1:4), and he is said to have formulated the syllogism that 'if the soul is not able to be without sin, then God too is subject to sin, since a part of him, namely, our soul, is subject to sin.' "106 If we participate in a sinless God, we too remain sinless (so went Augustine's understanding of how Caelestius used 2 Pet. 1:4).
105. Cf., en. Ps. 52.6: "Videte quae sit illa participatio: promissa est nobis participatio diuinitatis; mentitur qui promisit, si non est prior factus particeps mortalitatis"; CCL 39.642; c. s. Ar. 27.23: "Si autem non erunt, quomodo accipienda est illius plenitudo atque perfectio, nisi ut sit prorsus gignenti aequalis, et in nullo omnino dissimilis; atque ut id breuius planiusque dicamus, sint isti filii gratia, ille natura: quia in istis est participatio diuinitatis, in illo plenitudo?"; PL 42.702.
106. gest. Pel. 18.42: "et de apostolo Petro posuit testimonium, 'Diuinae nos esse consortes naturae' et syllogismum facere dicitur: 'quoniam si anima non potest esse sine peccato, ergo et deus subiacet peccato, cuius pars, hoc est anima, peccato obnoxia est' "; CSEL 42.98; Roland Teske, Pelagians (I/23), 364; cf. gest. Pel. 35.65 where Augustine's concern is again the use of 2 Pet. 1:4 to show how the soul can be "as sinless as God."