CIC 152 One cannot believe in Jesus Christ without sharing in his Spirit. It is the Holy Spirit who reveals to men who Jesus is. For “no one can say ”Jesus is Lord“, except by the Holy Spirit”,1 who “searches everything, even the depths of God. .. No one comprehends the thoughts of God, except the Spirit of God.”2 Only God knows God completely: we believe in the Holy Spirit because he is God.
The Church never ceases to proclaim her faith in one only God: Father, Son and Holy Spirit.

CIC 221 But St. John goes even further when he affirms that “God is love”:3 God’s very being is love. By sending his only Son and the Spirit of Love in the fullness of time, God has revealed his innermost secret:4 God himself is an eternal exchange of love, Father, Son and Holy Spirit, and he has destined us to share in that exchange.

CIC 446 In the Greek translation of the Old Testament, the ineffable Hebrew name YHWH, by which God revealed himself to Moses,5 is rendered as Kyrios, “Lord”. From then on, “Lord” becomes the more usual name by which to indicate the divinity of Israel’s God. The New Testament uses this full sense of the title “Lord” both for the Father and – what is new – for Jesus, who is thereby recognized as God Himself.6

CIC 498 People are sometimes troubled by the silence of St. Mark’s Gospel and the New Testament Epistles about Jesus’ virginal conception. Some might wonder if we were merely dealing with legends or theological constructs not claiming to be history. To this we must respond: Faith in the virginal conception of Jesus met with the lively opposition, mockery or incomprehension of non-believers, Jews and pagans alike;7 so it could hardly have been motivated by pagan mythology or by some adaptation to the ideas of the age. The meaning of this event is accessible only to faith, which understands in it the “connection of these mysteries with one another”8 in the totality of Christ’s mysteries, from his Incarnation to his Passover. St. Ignatius of Antioch already bears witness to this connection: “Mary’s virginity and giving birth, and even the Lord’s death escaped the notice of the prince of this world: these three mysteries worthy of proclamation were accomplished in God’s silence.”9

CIC 598 In her Magisterial teaching of the faith and in the witness of her saints, the Church has never forgotten that “sinners were the authors and the ministers of all the sufferings that the divine Redeemer endured.”10 Taking into account the fact that our sins affect Christ himself,11 the Church does not hesitate to impute to Christians the gravest responsibility for the torments inflicted upon Jesus, a responsibility with which they have all too often burdened the Jews alone:
We must regard as guilty all those who continue to relapse into their sins. Since our sins made the Lord Christ suffer the torment of the cross, those who plunge themselves into disorders and crimes crucify the Son of God anew in their hearts (for he is in them) and hold him up to contempt. And it can be seen that our crime in this case is greater in us than in the Jews. As for them, according to the witness of the Apostle, “None of the rulers of this age understood this; for if they had, they would not have crucified the Lord of glory.” We, however, profess to know him. And when we deny him by our deeds, we in some way seem to lay violent hands on him.12
Nor did demons crucify him; it is you who have crucified him and crucify him still, when you delight in your vices and sins.13

CIC 1027 This mystery of blessed communion with God and all who are in Christ is beyond all understanding and description. Scripture speaks of it in images: life, light, peace, wedding feast, wine of the kingdom, the Father’s house, the heavenly Jerusalem, paradise: “no eye has seen, nor ear heard, nor the heart of man conceived, what God has prepared for those who love him.”14

CIC 1998 This vocation to eternal life is supernatural. It depends entirely on God’s gratuitous initiative, for he alone can reveal and give himself. It surpasses the power of human intellect and will, as that of every other creature.15

CIC 2038 In the work of teaching and applying Christian morality, the Church needs the dedication of pastors, the knowledge of theologians, and the contribution of all Christians and men of good will. Faith and the practice of the Gospel provide each person with an experience of life “in Christ,” who enlightens him and makes him able to evaluate the divine and human realities according to the Spirit of God.16 Thus the Holy Spirit can use the humblest to enlighten the learned and those in the highest positions.

1 I Cor 12:3.
2 I Cor 2:10-11.
3 l Jn 4:8, 16.
4 Cf. I Cor 2:7-16; Eph 3:9-12.
5 Cf. Ex 3:14.
6 Cf. I Cor 2:8.
7 Cf. St. Justin, Dial. 99, 7: PG 6, 708-709; Origen, Contra Celsum 1, 32, 69: PG 11, 720-721; et al.
8 Dei Filius 4: DS 3016.
9 St. Ignatius of Antioch, Ad Eph. 19, 1: AF 11/2 76-80: cf. I Cor 2:8.
10 Roman Catechism I, 5, 11; cf. Heb 12:3.
11 Cf. Mt 25:45; Acts 9:4-5.
12 Roman Catechism I, 5, 11; cf. Heb 6:6; 1 Cor 2:8.
13 St. Francis of Assisi, Admonitio 5, 3.
14 1 Cor 2:9.
15 Cf. 1 Cor 2:7-9.
16 Cf. 1 Cor 2:10-15.