The First Epistle of John makes it clear that fellowship with the Spirit has a definite empirical aspect. The Spirit makes us know that Jesus remains in us (see 1 Jn 3.24). The Spirit makes it clear to us that we are in God and God in us (see 1 Jn 4.13). How does he do this?

In seeking to answer this question, one is tempted to look for the extraordinary and to ignore the ordinary manifestation of the Spirit in Christian life. Faith itself really is quite remarkable, for by it we can adhere with absolute assurance and steadiness to our heavenly Father, accept and defend the mysterious truth of our Lord Jesus, and remain relatively calm amidst great difficulties (see 2 Cor 5.16–6.10; Heb 11; 1 Jn 4.1–6). Faith is aroused and sustained by the Spirit (see LG 12). Thus, people conscious of the firmness and effective power of the living faith that is in them have empirical evidence of the gift of the Spirit (see S.t., 2–2, q. 6, a. 1).

The prophets hoped for the Spirit to enable God’s people to keep his word. Christians who cooperate with grace can experience this power of the Spirit in their lives. Thus anyone who lives a Christian life and experiences growth in likeness to Jesus has personal experience of the continuing presence of the Spirit (see S.t., 1–2, q. 106, a. 1; q. 112, a. 5).

Of course, at times there are extraordinary manifestations of the presence of the Spirit (see 1 Cor 12.8–10). But living faith working through love is a greater gift and a surer experience of the fellowship of the Spirit than is any extraordinary occurrence, since such occurrences can be the work of spirits other than the Holy Spirit (see 1 Jn 4.1).

In the past, many Christians lacked reflective awareness of the presence and work of the Spirit. Devotion to one’s guardian angel, while excellent in itself, sometimes served as a substitute for the devotion we ought to have to the Holy Spirit. He is ever at our side; we are committed to his care by God’s love; he lights, guards, rules, and guides us in the way of the Lord Jesus. Today, in contrast with the past, some may be pressing to excess a desire for intense, explicit awareness of the presence of the Spirit. In my view, each of the three divine persons should be present in our religious experience somewhat differently from the others.

The Father revealed himself as the transcendent God; we ought to be aware of his presence in creation, in the given realities of faith and Christian life, and in the demands which Christian morality makes upon our consciences. The Son revealed himself to us by coming among us as man, as another man like us; we ought to be aware of his presence in the Liturgy, in the leaders and fellow members of the Church, in the needs of all men and women. The Spirit reveals himself to us as a mentor in living the divine life; we ought to be aware of his presence as God with us, alongside us in our Christian lives.

A young brain surgeon assisting in a delicate operation is adequately aware of the more experienced colleague, who is the chief of the operating team, if the younger surgeon collaborates smoothly and adaptably. The junior physician cannot do this effectively if he or she pays attention to the elder colleague as he or she would to a dinner companion or to the chief of staff’s address to a conference. Not yet face to face, but already side by side, the Christian rejoices in the experience of the Holy Spirit.

By this analogy I by no means wish to suggest that the adopted child of God is equal to the uncreated Spirit. Since he is the natural Spirit of God and we the adopted children, the fruit of our common work primarily is his. The Spirit is the soul of the Church; the Church is our mother in Jesus, the mother of all God’s little ones. We might well think of ourselves as embryonic children, snug in the womb of the Church, dependent for our divine life upon the Spirit, much as a natural embryo depends for all its life and functioning upon its mother.

In heaven we hope to enjoy in the exercise of our native human capacities a great awareness of the divine persons with whom we will be sharing our entire lives, including our lives as the particular human individuals we are. But even now we have some experience of the three divine persons with us. It varies from the experience we all have at times of God’s closeness in our prayers and our daily work to the experience of a martyr like St. Stephen (see Acts 7.55–56) or a mystic like St. John of the Cross.