God the Holy Spirit is the third person of the Trinity
After Vatican Council II, Pope Paul VI called for “a new study of and devotion to the Holy Spirit, precisely as the indispensable complement to the teaching of the Council” (General Audience of June 6, 1973). It must be affirmed in any study of the Holy Spirit that he is indeed a Person who (as the Nicene Creed states) proceeds from the Father and the Son, and that as the third Person of the Trinity, he is God.
The Holy Spirit is, sadly, not understood by all Christians to be both Person and God. While most Christians can accept God the Father and God the Son as Persons and as God, the Holy Spirit is seen by some as an entity on a different level and is even reduced by some Christian churches to a kind of force that God possesses rather than God himself. But “Christians are baptized in the name of the Father and of the Son and of the Holy Spirit: not in their names, for there is only one God, the almighty Father, his only Son and the Holy Spirit: the Most Holy Trinity” (CCC 233).
The Catholic teaching about the Holy Spirit derives, as Blessed John Paul II pointed out, from “the very source of her faith, Jesus Christ.” Jesus attests to the personal nature of the Holy Spirit: "When the Advocate comes whom I will send you from the Father, the Spirit of truth that proceeds from the Father, he will testify to me” (John 15:26). The Catechism explains that “at work since creation, having previously ‘spoken through the prophets,’ the Spirit will now be with and in the disciples, to teach them and guide them ‘into all the truth.’ The Holy Spirit is thus revealed as another divine person with Jesus and the Father” (CCC 243).
Scripture and Catholic teaching are loaded with references to the Holy Spirit that make clear his nature as person and God and his mission to lead God’s people into the truth. The study called for by Paul VI must take these sources as the ones the Spirit has given us to come to a deeper knowledge of him.