One

48. How does the Church express her trinitarian faith?
249-256
266
The Church expresses her trinitarian faith by professing a belief in the oneness of God in whom there are three Persons: Father, Son, and Holy Spirit. The three divine Persons are only one God because each of them equally possesses the fullness of the one and indivisible divine nature. They are really distinct from each other by reason of the relations which place them in correspondence to each other. The Father generates the Son; the Son is generated by the Father; the Holy Spirit proceeds from the Father and the Son.

Holy Spirit

47. Who is the Holy Spirit revealed to us by Jesus Christ?
243-248
The Holy Spirit is the third Person of the Most Blessed Trinity. He is God, one and equal with the Father and the Son. He “proceeds from the Father” (John 15:26) who is the principle without a principle and the origin of all trinitarian life. He proceeds also from the Son (Filioque) by the eternal Gift which the Father makes of him to the Son. Sent by the Father and the Incarnate Son, the Holy Spirit guides the Church “to know all truth” (John 16:13).

Father

46. What did Jesus Christ reveal to us about the mystery of the Father?
240-242 

Jesus Christ revealed to us that God is “Father”, not only insofar as he created the universe and the mankind, but above all because he eternally generated in his bosom the Son who is his Word, “ the radiance of the glory of God and the very stamp of his nature” (Hebrews 1:3).

Source

45. Can the mystery of the Most Holy Trinity be known by the light of human reason alone?
237 

God has left some traces of his trinitarian being in creation and in the Old Testament but his inmost being as the Holy Trinity is a mystery which is inaccessible to reason alone or even to Israel’s faith before the Incarnation of the Son of God and the sending of the Holy Spirit. This mystery was revealed by Jesus Christ and it is the source of all the other mysteries.

Family

44. What is the central mystery of Christian faith and life?
232-237 

The central mystery of Christian faith and life is the mystery of the Most Blessed Trinity. Christians are baptized in the name of the Father and of the Son and of the Holy Spirit.

unity and true dignity of all human beings

43. What does it mean to believe in only one God?
222-227
229

To believe in the one and only God involves coming to know his greatness and majesty. It involves living in thanksgiving and trusting always in him, even in adversity. It involves knowing the unity and true dignity of all human beings, created in his image. It involves making good use of the things which he has created.

Love

42. In what way does God reveal that he is love?
218-221

God revealed himself to Israel as the One who has a stronger love than that of parents for their children or of husbands and wives for their spouses. God in himself “is love” (1 John 4: 8.16), who gives himself completely and gratuitously, who “so loved the world that he gave his only Son so that the world might be saved through him” (John 3:16-17). By sending his Son and the Holy Spirit, God reveals that he himself is an eternal exchange of love.