1. Spiritual life needs enlightenment and guidance. This is why Jesus, in founding the Church and sending the Apostles into the world, entrusted them with the task of teaching all the nations, as we read in the Gospel according to Matthew (Mt 28:19-20), but also to "preach the Gospel to the whole creation", as the canonical text of Mark's Gospel says (Mk 16:15). St Paul also speaks of the apostolate as "enlightening everyone" (Eph 3:9).
But this work of the evangelising and teaching Church belongs to the ministry of the Apostles and their successors and, in a different capacity, to all the members of the Church, to continue forever the work of Christ the "one Master" (Mt 23:8), who brought to humanity the fullness of God's revelation. There remains the need for an interior Master, who makes the teaching of Jesus penetrate the spirit and heart of mankind. It is the Holy Spirit, whom Jesus himself calls the "Spirit of truth", and whom he promises as the One who will guide into all truth (cf. Jn 14:17; 16:13). If Jesus said of Himself: "I am the truth" (Jn 14:6), it is this truth of Christ that the Holy Spirit makes known and spreads: "He will not speak of Himself, but will tell all that He has heard . . . he will take of mine and proclaim it to you" (Jn 16:13-14). The Spirit is Light of the soul: "Lumen cordium", as we invoke it in the Pentecost Sequence.
2. The Holy Spirit was Light and inner Master for the Apostles who had to know Christ in depth in order to fulfil their task as his evangelisers. He was and is so for the Church, and, in the Church, for believers of all generations, and especially for theologians and teachers of the Spirit, for catechists and leaders of Christian communities. It has been and is also for all those who, within and outside the visible confines of the Church, wish to follow God's ways with a sincere heart, and through no fault of their own find no one to help them decipher the riddles of the soul and discover the revealed truth. May the Lord grant all our brothers and sisters - millions and indeed billions of men - the grace of recollection and docility to the Holy Spirit in moments that can be decisive in their lives.
For us Christians, the intimate teaching of the Holy Spirit is a joyful certainty, based on Christ's word about the coming of the 'other Paraclete', whom - he said - 'the Father will send in my name. He will teach you all things and bring to your remembrance all that I have spoken to you" (John 14:26). "He will guide you into all truth" (Jn 16:13).
3. As is clear from this text, Jesus does not entrust his word only to the memory of his hearers: this memory will be aided by the Holy Spirit, who will continually revive in the apostles the memory of events and the sense of the mysteries of the Gospel.
In fact, the Holy Spirit guided the Apostles in the transmission of the word and life of Jesus, inspiring both their oral preaching and writings, as well as the writing of the Gospels, as we have seen in the catechesis on the Holy Spirit and Revelation.
But it is still He who gives the readers of Scripture the help to understand the divine meaning included in the text of which He Himself is the inspirer and main author: He alone can make known "the depths of God" (1 Cor 2:10), as they are contained in the sacred text; He who was sent to instruct the disciples on the teachings of their Master (cf. Jn 16:13).
4. Of this intimate teaching of the Holy Spirit the Apostles themselves, the first transmitters of the word of Christ, speak to us. St. John writes: "Now you have the anointing received from the Holy One (Christ) and you are all taught. I have not written to you because you do not know the truth, but because you know it and because no lie comes from the truth" (1 John 2: 20-21). According to the Church Fathers and the majority of modern exegetes, this "anointing" (chrisma) designates the Holy Spirit. Indeed, St John states that those who live according to the Spirit have no need of other teachers: "As for you," he writes, "the anointing you have received from Him abides in you, and you do not need anyone to teach you; but just as His anointing teaches you all things, and is true and does not lie, so stand firm in Him, as He teaches you" (1 John 2: 27).
The Apostle Paul also speaks of an understanding according to the Spirit, which is not the result of human wisdom, but of divine illumination: "The natural man (psychicòs) does not understand the things of the Spirit of God; they are foolishness to him, and he is not able to understand them, because he can judge of them only by the Spirit. The spiritual man (pneumaticòs), on the other hand, judges everything, without being able to be judged by anyone" (1 Cor 2:14-15).
Therefore Christians, having received the Holy Spirit, Christ's anointing, possess within themselves a source of knowledge of the truth, and the Holy Spirit is the sovereign Master who enlightens and guides them.
5. If they are docile and faithful to his divine teaching, the Holy Spirit preserves them from error, making them victorious in the constant conflict between the "spirit of truth" and the "spirit of error" (cf. 1 Jn 4:6). The spirit of error, which does not recognise Christ (cf. 1 Jn 4:3), is spread by the "false prophets", ever present in the world, even in the midst of the Christian people, with an action that is now uncovered and even clamorous, now insidious and creeping. Like Satan, they too sometimes disguise themselves as "angels of light" (cf. 2 Cor 11:14) and present themselves with apparent charisms of prophetic and apocalyptic inspiration. This was already the case in apostolic times. That is why St John warns: "Do not put faith in every inspiration, but test the inspirations, to see if they really come from God, for many false prophets have appeared in the world" (1 John 4:1). The Holy Spirit, as the Second Vatican Council recalled (cf. Lumen gentium, 12), protects the Christian from error by making him discern what is genuine from what is spurious. On the part of the Christian, it will always take good criteria of discernment regarding the things he hears or reads in matters of religion, Holy Scripture, manifestations of the supernatural, etc. Such criteria are conformity to the Gospel, because the Holy Spirit cannot but "take from Christ"; harmony with the teaching of the Church, founded and sent by Christ to preach its truth; the uprightness of the life of the speaker or writer; the fruits of holiness resulting from what is presented or proposed.
6. The Holy Spirit teaches the Christian the truth as the principle of life. It shows the concrete application of Jesus' words in one's life. It makes one discover the relevance of the Gospel and its value for all human situations. It adapts the understanding of the truth to every circumstance, so that this truth does not remain merely abstract and speculative, and frees the Christian from the dangers of duplicity and hypocrisy.
This is why the Holy Spirit enlightens each one personally, to guide him in his behaviour, showing him the way to follow, opening up at least some glimmer of the Father's plan for his life. This is the great grace of light that St Paul asked for the Colossians: "spiritual intelligence", capable of making them understand the divine will. Indeed, he assured them: "We do not cease to pray for you and to ask that you have a full knowledge of his (God's) will with all wisdom and spiritual intelligence, that you may conduct yourselves in a manner worthy of the Lord, to please him in all things, bearing fruit in every good work . . ." (Col 1:9-10). This grace of light is necessary for all of us, to know God's will for us well and to be able to live our personal vocation fully.
There is never a shortage of problems, which sometimes seem insoluble. But the Holy Spirit comes to the aid of difficulties and enlightens. He can reveal the divine solution, as at the Annunciation for the problem of reconciling motherhood with the desire to preserve virginity. Even when it is not a unique mystery such as that of Mary's intervention in the Incarnation of the Word, it can be said that the Holy Spirit possesses an infinite inventiveness, proper to the divine mind, which knows how to unravel the knots of even the most complex and impenetrable human affairs.
7. All this is granted and worked in the soul by the Holy Spirit through his gifts, thanks to which it is possible to practise good discernment not according to the criteria of human wisdom, which is foolishness before God, but of divine wisdom, which may seem foolishness in the eyes of men (cf. 1 Cor 1:18, 25). In reality, only the Spirit "searches all things, even the depths of God" (1 Cor 2:10-11). And if there is opposition between the spirit of the world and the Spirit of God, Paul reminds Christians: "We have not received the spirit of the world, but the Spirit of God to know all things that God has given us" (1 Cor 2:12). Unlike the "natural man", the "spiritual man" (pneumaticòs) is sincerely open to the Holy Spirit, docile and faithful to his inspirations (cf. 1 Cor 2:14-16). Therefore he habitually has the capacity for right judgement under the guidance of divine wisdom.
8. A sign of real contact with the Holy Spirit in discernment is and always will be adherence to revealed truth as proposed by the Magisterium of the Church. The interior Master does not inspire dissension, disobedience, or even unjustified resistance to the pastors and teachers established by Him in the Church (cf. Acts 20:29). It is the authority of the Church, as the Council says in the constitution Lumen gentium, "not to quench the Spirit, but to examine everything and hold fast to what is good (cf. 1 Thess 5:12, 19-21)" (Lumen gentium, 12). This is the line of ecclesial and pastoral wisdom that also comes from the Holy Spirit.
[Pope John Paul II, General Audience 24 April 1991]