On 9th May, 1897, Pope Leo XIII issued his Encyclical Letter Divinum Illud Munus on the Holy Ghost:
"5. The Church which, already conceived, came forth from the side of the second Adam in His sleep on the Cross, first showed herself before the eyes of men on the great day of Pentecost. On that day the Holy Ghost began to manifest His gifts in the mystic body of Christ, by that miraculous outpouring already foreseen by the prophet Joel (ii., 28-29), for the Paraclete "sat upon the apostles as though new spiritual crowns were placed upon their heads in tongues of fire" (S. Cyril Hier. Catech. 17). Then the apostles "descended from the mountain," as St. John Chrysostom writes, "not bearing in their hands tables of stone like Moses, but carrying the Spirit in their mind, and pouring forth the treasure and the fountain of doctrines and graces" (In Matt. Hom. 1., 2 Cor. iii., 3). Thus was fully accomplished that last promise of Christ to His apostles of sending the Holy Ghost, who was to complete and, as it were, to seal the deposit of doctrine committed to them under His inspiration. "I have yet many things to say to you, but you cannot bear them now; but when He, the Spirit of Truth, shall come, He will teach you all truth" (John xvi., 1213). For He who is the Spirit of Truth, inasmuch as He proceedeth both from the Father, who is the eternally True, and from the Son, who is the substantial Truth, receiveth from each both His essence and the fullness of all truth. This truth He communicates to His Church, guarding her by His all powerful help from ever falling into error, and aiding her to foster daily more and more the germs of divine doctrine and to make them fruitful for the welfare of the peoples. And since the welfare of the peoples, for which the Church was established, absolutely requires that this office should be continued for all time, the Holy Ghost perpetually supplies life and strength to preserve and increase the Church. "I will ask the Father, and He will give you another Paraclete, that He may abide with you for ever, the Spirit of Truth" John xiv., 16, 17)."
"6. By Him the bishops are constituted, and by their ministry are multiplied not only the children, but also the fathers - that is to say, the priests - to rule and feed the Church by that Blood wherewith Christ has redeemed Her. "The Holy Ghost hath placed you bishops to rule the Church of God, which He hath purchased with His own Blood" (Acts xx., 28). And both bishops and priests, by the miraculous gift of the Spirit, have the power of absolving sins, according to those words of Christ to the Apostles: "Receive ye the Holy Ghost; whose sins you shall forgive they are forgiven them, and whose you shall retain they are retained" John xx., 22, 23). That the Church is a divine institution is most clearly proved by the splendour and glory of those gifts and graces with which she is adorned, and whose author and giver is the Holy Ghost. Let it suffice to state that, as Christ is the Head of the Church, so is the Holy Ghost her soul. "What the soul is in our body, that is the Holy Ghost in Christ's body, the Church" (St. Aug., Serm. 187, de Temp.). This being so, no further and fuller "manifestation and revelation of the Divine Spirit" may be imagined or expected; for that which now takes place in the Church is the most perfect possible, and will last until that day when the Church herself, having passed through her militant career, shall be taken up into the joy of the saints triumphing in heaven."