424 THE HOLY SPIRIT.
cially that piety may increase and be inflamed towards the Holy Ghost, to whom especially all of us owe the grace of following the paths of truth and virtue, for, as St. Basil said, "Who denieth that the dispensations concerning man, which have been made by the great God and our Saviour Jesus Christ, according to the goodness of God, have been fulfilled through the grace of the Spirit?" *
Before We enter upon this subject, it will be both desir- able and useful to say a few words about the mystery of the Blessed Trinity. This dogma is called by the Doctors of the Church "the substance of the New Testament," that is to say, the greatest of all mysteries, since it is the fountain and origin of them all. In order to know and contemplate this mystery, the angels were created in heaven and men upon earth. In order to teach more fully this mystery, which was but foreshadowed in the Old Testament, God Himself came down from the angels unto men: No man hath seen God at any titne; the only begotten Son, who is in the bosom of the Father, He hath declared Him? Who- soever then writes or speaks of the Trinity must keep before His eyes the prudent warning of the Angelic Doctor: "When we speak of the Trinity, we must do so with cau- tion and modesty, for, as St. Augustine saith, nowhere else are more dangerous errors made, or is research more difficult, or discovery more fruitful" ^ The danger that arises is lest the divine persons be confounded one with the other in faith or worship, or lest the one nature in them be separated: for "This is the Catholc faith, that we should adore one God in Trinity and Trinity in Unity." Therefore Our predecessor Innocent XII. absolutely refused the petition of those who desired a special festival in honor of God the Father. For, although the separate mysteries connected with the Incarnate Word are celebrated on cer- tain fixed days, yet there is no special feast on which the Word is honored according to His divine nature alone.
1 Of the Holy Ghost, c. xvi., v. 39. => John i. 18.
' Summ. Th. la., q. xxxi. De Tiin. 1. i., c. 3.
