In His discourse at the Last Supper our Blessed Lord mentioned the three Persons by name, and He clearly spoke of the doctrine of the Holy Trinity to the apostles just before He ascended into heaven. The texts of Sacred Scripture containing these words of Christ have been given in this lesson. There was also a. external manifestation of the Holy Trinity at the time of Our Lord's baptism by St. John in the river Jordan. On that occasion it was God the Son in His human nature who was baptized, while God the Holy Ghost descended on Him in the form of a dove and God the Father announced from heaven: "This is my beloved Son, in whom I am well pleased" (Matthew 3:17).
Hence, according to Catholic belief, there are three divine Persons but only one divine nature. All three Persons are perfectly equal to each other, because all possess the same divine nature with all its infinite perfections. From all eternity the Son proceeds from the Father as the Word, the product of the intellectual act whereby the Father understands the divine nature, and the Holy Ghost proceeds from the Father and the Son as the product of the act of love of these two Persons for the divine goodness. All the actions of God outside of those whereby the second and third Persons proceed are acts of the three Persons operating together through the one divine nature. However, certain works performed by all three Persons are appropriated or attributed to particular Persons as if they individually performed them for example, the work of creation to the Father, the work of producing the human nature of Christ to the Holy Ghost (Luke 1:35); but only the Second Person became incarnate.
Although the doctrine of the Blessed Trinity is a supernatural mystery A truth which we cannot discover by reason nor understand in the present life we believe it because it has been made known to us by God who can neither deceive nor be deceived. Even in natural things there are many mysteries which We accept on the testimony of our fellow men. We believe what the astronomers tell us about the stars and the planets, although we cannot prove these truths ourselves. Not even the most learned scientist understands fully the nature of the force we call electricity; yet we all know that there is such a force and we unhesitatingly accept the information that scientists give us about it. How much more willing should we be to believe the marvelous truth which God Himself has made known to us that He is one in nature and three in Persons even though we cannot perceive this truth by our own reason nor understand how each divine Person can be identical with the divine nature, yet really distinct from the other two Persons!
On the first Sunday after Pentecost the Church celebrates a feast in honor of the Most Blessed Trinity. Moreover, on Sundays outside of the Christmas, Lenten and Easter seasons the Preface of the Holy Trinity is recited or chanted in the Mass. One of the favored devotions of the Catholic Church is the Doxology the prayer: "Glory be to the Father and to the Son, and to the Holy Ghost. As it was in the beginning, is now, and ever shall be, world without end Amen." This Doxology is frequently repeated in the official prayers of the Church, particularly in the Divine Office which priests and the members of religious orders recite every day. And whenever we make the Sign of the Cross we profess our faith in the mystery of the Most Blessed Trinity.
RESOLUTION: Whenever you recite the Doxology or make the Sign of the Cross, try to remember that you are expressing your faith in the most profound mystery of the Catholic religion, the mystery of the Most Blessed Trinity.