Presence of the Holy Spirit in a person who is in the state of grace. He is present not only by means of the created gifts of grace, which he dispenses, but by his uncreated divine nature. This personal indwelling does not produce a substantial but only an accidental union with the souls of the just. As the indwelling of the Holy Spirit is an operation of God outside himself and as all activity of God outside the Trinity is common to the three persons, the indwelling of the Holy Spirit implies the indwelling of the three divine persons. This indwelling as a manifestation of the love of God, the personal love of the Father and the Son, is appropriated to the Holy Spirit. St. Paul speaks of the third person: "Know you not that you are the temples of God and that the Spirit of God dwells in you" (I Corinthians 3:16). But he also says: "You are the temple of the living God" (I Corinthians 6:16), and Christ declares: "If any one loves me, he will keep my word. And my father will love him; and we will come to him and will make our abode with him" (John 14:23).
The immediate effect of the divine indwelling is sanctifying grace, which is the created result of the uncreated grace of God's presence. Its effect on the person is an experience that spiritual writers compare to a foretaste of the beatific vision; the mind is able to understand something of the mystery of God and the will is enamored of his goodness beyond anything possible by the light of reason or the natural affective powers of humans.