The Acts of the Apostles emphasizes the Holy Spirit's role in the spreading of the Gospel and in charisms such as prophecy and speaking in tongues. But while St. Paul was a primary actor in the spread of the Gospel and he recognized the importance of charisms, his emphasis was different.
When St. Paul spoke of the fruit of the Holy Spirit, he spoke not of conversions or charisms, but of love, joy, peace, patience, gentleness, self-control, etc. For Paul, a faithful Jew, the Holy Spirit made it possible for God's people to live up to the precepts of the Mosaic Law.
With his covenant, God had built a bridge to humanity. The most important part of the covenant was the Law. The psalmist prayed, "Happy are those whose way is blameless, who walk in the Law of the Lord" (Psalm 119.1). The Psalms and other Old Testament writings are replete with praises of the glory of God's Law.
But Paul could not but notice that no one is without sin, that none are able to walk faithfully in the Law. Israel was congenitally unfaithful. It possessed the Law, but did not live it.
This is the major theme of the early chapters of Paul's letter to the Romans - not simply that the Jews were unable to live up to the Law, but that it actually led them to sin. While the Law itself is holy because it is God's Law, the attempt to live out the Law is not only impossible, it is "the ministry of death" (2 Corinthians 3.7).
Even at the moment that Moses brought the Law down from Sinai, Israel was engaged in idol worship. God responded to that infidelity by giving Israel more and more laws to follow. But instead of eliminating sin, knowledge of the Law led to an increase in sin. "The very commandment which promised life proved to be death to (Israel)" (Romans 7.10).
It is little wonder that Paul met serious difficulties when he proclaimed the Gospel in local synagogues on his travels.
Paul maintained that God's purpose in introducing the Law was to increase the power of sin in the world. Why would God do such a thing? He did it so that God's power could be revealed definitively through Christ's cross and resurrection. He did it so that we would know that we cannot achieve salvation without God's constant help.
The answer to sin is not Law, but "the law of the Spirit of life in Christ Jesus" (Romans 8.2). The New Law given through Jesus the Messiah is not a better set of commands. Nor is the New Law the replacement of laws with love.
The fulfillment of the covenant, rather, is the Holy Spirit dwelling within us. In the Old Testament, God stood by his people; now he actually lives within them.
God sent his Son "so that the just requirement of the Law might be fulfilled in us, who walk not according to the flesh but according to the Spirit" (Romans 8.4). The Holy Spirit is the life of God within us enabling us to fulfill the Law.
Christian moral living is based on this fundamental truth. The effectiveness of the sacraments and the virtues of faith, hope and charity all hang on the power of the Spirit animating our lives. Without the Holy Spirit, we are lost; with the Spirit, our lives are transformed.
The Catechism of the Catholic Church says God's love poured into our hearts through the Holy Spirit enables us to act out of love rather than out of a fear of the consequences of not obeying the Law. The New Law is a law of freedom because it enables us to act prompted by charity rather than by performing prescribed rituals. We have become friends of Christ, even heirs to the kingdom and children of God by adoption (n. 1972).
Thanks to the outpouring of the Holy Spirit, God's people are capable of walking in the Law of the Lord. Happiness is possible. So are joy and peace and love. We receive the Holy Spirit through Baptism and through all the sacraments.
But we need to pray for a fresh outpouring on ourselves and on all God's people. This is the way that sin and death are conquered and God's reign comes alive in our world.