As difficult as it is to describe what exactly the Holy Spirit is, we can draw a pretty good idea, especially with the help of the Scriptures, of what the Holy Spirit does, both in terms of the Trinity itself and in the life of the Church.
In the Trinity, the Spirit is what is shared, common between the Father and the Son – he is the unity between them, the “fruitfulneess of their act of giving,” and by this, “they are One” (Ratzinger 109).
It is in Scripture that we can come to a fuller idea of what the Spirit does and how the Spirit works in the life of the Church. John’s gospel gives a telling image of the Holy Spirit: “the Spirit is the breath of the Son.” While Jesus is alive, the Spirit resides in Jesus alone, but when the Son ascends, this makes possible the pouring out of the Spirit which occurs at Pentecost. This feast is often referred to as the “birth of the Church” because the Spirit is indeed what gave life to the Church. While Jesus was on this earth, there was no need for the Spirit, but after he ascended, he gave his Spirit so that it may draw us to Him. Since the Spirit is the breath of the Son, then when we receive the Spirit, we are led to the Son, and then through the Son to the Father.
The Spirit leads us in this eternal “process of discovery” of the Word, which leads us to the Father. It is inseparable from the Father and the Son, for “Every spirit which confesses that Jesus Christ has come in the flesh is of God, and very spirit which does not confess Jesus is not of God” (1 Jn 4:2), and they are all Love, The Spirit is the “architect” which places the Son at the head of the Church, and pours His life into the life of the Church: through the sacraments and all liturgical life. The Spirit is present in Scripture, carrying and interpreting the message, and in all prayer and contemplation. We may even say the Spirit is the breath of any prayer, for our prayer goes to Christ and to the Father.
In the modern imagination, the individual tends to focus on itself, and interpreting everything in light of its own knowledge and experience. The Spirit, however, guides us to look towards Christ, and to our Father. The Spirit moves us and works through us by the gifts it gives us, and we are to recognize that these come from God. The Holy Spirit is the life of the Church and how we can individually see God working in our lives. Being receptive to these gifts and through the Spirit learning to direct our gaze to God is to be open to the transforming power of God in our lives.