The Holy Spirit is the third person of the Holy Trinity.  He reigns with Our Father and Jesus Christ.  This belief was expressed from the earliest days of the Church in the Apostles Creed.  It professes faith in the Holy Trinity — Father, Son (Jesus) and the Holy Spirit.  It states the following about the Holy Spirit:

“I believe in the Holy Spirit, the holy Catholic Church and the communion of saints, …”
Apostles Creed

This Creed was revised and expanded at the Council of Nicene (325 A.D.) and was called the Nicene Creed.  It is the same prayer we use today.  It states the following about the Holy Spirit:

“We believe in the Holy Spirit, the Lord, the giver of life who proceeds from the Father and Son.  With the Father and the Son he is worshiped and glorified.  He has spoken through the Prophets.”
Nicene Creed

A copy of both the Apostles Creed and the Nicene Creed are found on the Vatican website.  Here is a link to the “home” page on the Vatican website.

The Holy Spirit and Jesus have a joint mission in the world.  The Catechism of the Catholic Church (CCC) states:

“The One whom the Father has sent into our hearts, the Spirit of his Son, is truly God.  Consubstantial with the Father and the Son, the Spirit is inseparable from them, in both the inner life of the Trinity and his gift of love for the world.  In adoring the Holy Trinity, life-giving, consubstantial, and indivisible, the Church’s faith also professes the distinction of persons.  When the Father sends his Word, he always sends his Breath.  In their joint mission, the Son and the Holy Spirit are distinct but inseparable.  To be sure, it is Christ who is seen, the visible image of the invisible God, but it is the Spirit who reveals him.”
CCC 689

“Jesus is Christ, “anointed,” because the Spirit is his anointing, and everything that occurs from the Incarnation on derives from this fullness.  When Christ is finally glorified, he can in turn send the Spirit from his place with the Father to those who believe in him: he communicates to them his glory, that is, the Holy Spirit who glorifies him.  From that time on, this joint mission will be manifested in the children adopted by the Father in the Body of his Son: the mission of the Spirit of adoption is to unite them to Christ and make them live in him . . .”
CCC 690

The Catechism of the Catholic Church provides the following response:

“No one comprehends the thoughts of God except the Spirit of God.”  Now God’s Spirit, who reveals God, makes known to us Christ, his Word, his living Utterance, but the Spirit does not speak of himself.  The Spirit who “has spoken through the prophets” makes us hear the Father’s Word, but we do not hear the Spirit himself.  We know him only in the movement by which he reveals the Word to us and disposes us to welcome him in faith.  The Spirit of truth who “unveils” Christ to us “will not speak on his own.”  Such properly divine self-effacement explains why “the world cannot receive (him), because it neither sees him nor knows him,” while those who believe in Christ know the Spirit because he dwells with them.”
CCC 687

“The Church, a communion living in the faith of the apostles which she transmits, is the place where we know the Holy Spirit:

• in the Scriptures he inspired;
• in the Tradition, to which the Church Fathers are always timely witnesses;
• in the Church’s Magisterium, which he assists;
• in the sacramental liturgy, through its words and symbols, in which the Holy Spirit puts us into communion with Christ;
• in prayer, wherein he intercedes for us;
• in the charisms and ministries by which the Church is built up;
• in the signs of apostolic and missionary life;
• in the witness of saints through whom he manifests his holiness and continues the work of salvation.”
  – CCC 688

On the following pages, we will explore further the works, signs and symbols of the Holy Spirit and how His actions influence and affect our daily lives.