The One Christ: St. Augustine's Theology of Deification
168 The Holy Spirit's Indwelling but God?" Here at De Trinitate 8.8.12 the three effects of the Spirit's presence are again obvious: unity, love, and holiness. The phrase "full of God" (Deo plenus) insists that the Spirit is clearly not some external gift independent of God but is presented as the very life of God now inhabiting the human soul. We saw above how Augustine allows us to maintain that God himself and not just an effect of God can dwell in the created soul. Now we see how this presence is ultimately charity: the love we have in Christ for our brothers and sisters is not only from God but is also simply God [non solum ex Deo sed etiam Deus].78 The same love which unites Father and Son allows the human person to love the whole of the Trinity because the love with which we love God proves to be the Spirit himself. For Augustine, it is essential to note that none of the other virtues is so given. All other gifts come from God but they are in no way identified with God. God is neither fides nor spes, although these do come to us from him [ab ipso nobis].79
As mentioned, Augustine is not concerned about how this takes place and never ventures a metaphysical analysis of how the divine can inhabit a created soul, but rather quickly affirms that the Spirit fills us in a great and tremendous way [magnopere implebimur Spiritu Sancto] and only through his indwelling will we have charity in us.80 This presence is so real and effective that, as the Spirit fills the faithful with himself, he leads them to the Father. This movement is how Augustine decided to conclude his great work on the Trinity:
So the love which is from God and is God is distinctively the Holy Spirit; through him the charity of God is poured out in our hearts, and through it the whole triad dwells in us [per quam nos tota inhabitet trinitas]. This is the reason why it is most apposite that the Holy Spirit, while being God, should also be called the gift of God. And
78. Trin. 8.8.12; Hill, Trinity, 253. 79. Trin. 15.17.27; CCL 50A.502; cf., s. 156.5. 80. Cf. s. 272B.7.