How does the Christian's life of prayer depend on the Holy Spirit?
1. St. Paul teaches that Christians need and receive the special help of the Holy Spirit to pray as they ought: "Likewise the Spirit helps us in our weakness; for we do not know how to pray as we ought, but the Spirit himself intercedes for us with sighs too deep for words. And he who searches the hearts of men knows what is the mind of the Spirit, because the Spirit intercedes for the saints according to the will of God" (Rom 8.26-27).
2. This passage is frequently taken to mean simply that the Spirit causes us to ask as we should and stirs right desires in us. There seems no reason, however, for excluding a more straightforward meaning of the Spirit "himself intercedes for us."
3. We have good grounds for thinking of ourselves as having distinct personal relationships with each of the three divine persons (24-C). The Holy Spirit is the gift given by the Father to those who ask (see Lk 11.13). The General Instruction to the Liturgy of the Hours teaches: "The unity of the Church at prayer is brought about by the Holy Spirit, who is the same in Christ (See Lk 10.21), in the whole Church, and in every baptized person."
According to the promise of Jesus, the Spirit comes and remains (see Jn14.16-18). He is not only with us as a principle, but present in person. The children of God are not left in loneliness like orphans. The Spirit instructs (see Jn 14.26). He defends and guides (see Jn 16.7-14; Gal 5.25). Because of the presence of the Spirit, we have a concrete realization that we are children of God (see Rom 8.16). We cry out to God: "Father!" (see Rom 8.15). The Spirit makes up for our infantile condition by helping us in our weakness (see Rom 8.26-27). He takes a personal interest in our growth in the Christian life (see Eph 4.30).
4. The work of the Spirit in the Christian's life of prayer might be explained as follows. Prayer is the basic act of Christian life. It is normally a work of living faith--in other words, a work of charity. In praying, God's children act toward him according to the divine nature which he has begotten in them through the gift of the Spirit, as St. Paul also teaches: "For all who are led by the Spirit of God are sons of God. For you did not receive the spirit of slavery to fall back into fear, but you have received the spirit of sonship. When we cry, 'Abba! Father!' it is the Spirit himself bearing witness with our spirit that we are children of God" (Rom 8.14-16). However, as undeveloped, embryonic children of God (see 1 Jn 3.2), we are not yet capable of acting fully by ourselves according to the nature we have from the Father; we do not yet "see him as he is," that is, experience the fullness of divine life.
5. The Spirit, who "is the Lord, the giver of life, who proceeds from the Father and the Son," therefore somehow mediates our relationship with them, supplying what we simply cannot supply ourselves, as a pregnant mother mediates her unborn child's relationships with its human father, with other people, and with the world at large, doing for it what it cannot yet do for itself.
6. Prayer is the fundamental category of Christian life, and the Christian's life of prayer depends on the Holy Spirit in the way explained. Therefore, the Christian's entire life is supplemented by the work of the Spirit.
7. Hence, the fact that the whole of Christian life is lived in the Spirit in no way means that the Holy Spirit fulfills any of the Christian's human responsibilities. Rather, just as Jesus' communion as Word with the Spirit is no substitute for his faithful fulfillment as man of his personal vocation, so Christians' life in the Spirit leaves them with undiminished moral responsibility.
Christian Moral Principles --Germain Grisez