✟ The Unity and Trinity of God ✟
The Doctrine of the Triune God
Revealed Truth (Defined Dogma)

In God there are three Persons; the Father, the Son and the Holy Spirit.
Each of the three Persons possesses the one (numerical) Divine Essence.

Lay Catechist Notes/Associated Doctrines
    Among the "strict mysteries" of our faith, none are more unknowable by reason alone than the mystery of the Trinity of Persons in God. God has to be a society of persons in order to manifest true love - this makes perfect sense. A God comprised of a single person would never be able to actualize any form of love other than self love, which is not true love. But truth this is; that the true God is comprised of three individual and unique persons (the Father, the Son, and the Holy Spirit) that all share the same Divine Essence.

    Associated Catholic Doctrine(s):
    1. "The Trinity of God can only be known through Divine Revelation." (sententia fidei proxima)
Divine Revelation (Scriptural Proof)
  • 26And he said: Let us make man to our image and likeness: and let him have dominion over the fishes of the sea, and the fowls of the air, and the beasts, and the whole earth, and every creeping creature that moveth upon the earth. 27And God created man to his own image: to the image of God he created him: male and female he created them. (Genesis 1:26-27)
  • 19Going therefore, teach ye all nations; baptizing them in the name of the Father, and of the Son, and of the Holy Ghost. (Matthew 28:19)
Catechism of the Catholic Church
  • 234 The mystery of the Most Holy Trinity is the central mystery of Christian faith and life. It is the mystery of God in Himself. It is therefore the source of all the other mysteries of faith, the light that enlightens them. It is the most fundamental and essential teaching in the "hierarchy of the truths of faith". The whole history of salvation is identical with the history of the way and the means by which the one true God, Father, Son and Holy Spirit, reveals himself to men "and reconciles and unites with himself those who turn away from sin".
  • 237 The Trinity is a mystery of faith in the strict sense, one of the "mysteries that are hidden in God, which can never be known unless they are revealed by God". To be sure, God has left traces of his Trinitarian being in his work of creation and in his Revelation throughout the Old Testament. But his inmost Being as Holy Trinity is a mystery that is inaccessible to reason alone or even to Israel's faith before the Incarnation of God's Son and the sending of the Holy Spirit.
  • 244 The eternal origin of the Holy Spirit is revealed in his mission in time. The Spirit is sent to the apostles and to the Church both by the Father in the name of the Son, and by the Son in person, once he had returned to the Father. The sending of the person of the Spirit after Jesus' glorification reveals in its fullness the mystery of the Holy Trinity.
  • 249 From the beginning, the revealed truth of the Holy Trinity has been at the very root of the Church's living faith, principally by means of Baptism. It finds its expression in the rule of baptismal faith, formulated in the preaching, catechesis and prayer of the Church. Such formulations are already found in the apostolic writings, such as this salutation taken up in the Eucharistic liturgy: "The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all."
  • 253 The Trinity is One. We do not confess three Gods, but one God in three persons, the "consubstantial Trinity". The divine persons do not share the one divinity among themselves but each of them is God whole and entire: "The Father is that which the Son is, the Son that which the Father is, the Father and the Son that which the Holy Spirit is, i.e. by nature one God." In the words of the Fourth Lateran Council (1215), "Each of the persons is that supreme reality, viz., the divine substance, essence or nature."
Ecumenical Council Documents
  • 2nd General Council of Constantinople (553)
    • Anathemas against the "Three Chapters":
      • "1. If anyone will not confess that the Father, Son and holy Spirit have one nature or substance, that they have one power and authority, that there is a consubstantial Trinity, one Deity to be adored in three subsistences or persons: let him be anathema. There is only one God and Father, from whom all things come, and one Lord, Jesus Christ, through whom all things are, and one holy Spirit, in "whom all things are."
      • "10. If anyone does not confess his belief that our lord Jesus Christ, who was crucified in his human flesh, is truly God and the Lord of glory and one of the members of the holy Trinity: let him be anathema."
    • "It tells us how to believe in the name of the Father and of the Son and of the holy Spirit: believing also, of course, that the Father, the Son and the holy Spirit have a single Godhead and power and substance, a dignity deserving the same honour and a co-eternal sovereignty, in three most perfect hypostases, or three perfect persons."

  • 3rd General Council of Constantinople (680)
    • "Following the five holy and universal synods and the holy and accepted fathers, and defining in unison, it professes our lord Jesus Christ our true God, one of the holy Trinity, which is of one same being and is the source of life, to be perfect in divinity and perfect in humanity, the same truly God and truly man, of a rational soul and a body; consubstantial with the Father as regards his divinity, and the same consubstantial with us as regards his humanity, like us in all respects except for sin; begotten before the ages from the Father as regards his divinity, and in the last days the same for us and for our salvation from the holy Spirit and the virgin Mary, who is properly and truly called mother of God, as regards his humanity; one and the same Christ, Son, Lord, only-begotten, acknowledged in two natures which undergo no confusion, no change, no separation, no division; at no point was the difference between the natures taken away through the union, but rather the property of both natures is preserved and comes together into a single subsistent being [in unam personam et in unam subsistentiam concurrente]; he is not parted or divided into two persons, but is one and the same only-begotten Son, Word of God, lord Jesus Christ, just as the prophets taught from the beginning about him, and as Jesus the Christ himself instructed us, and as the creed of the holy fathers handed it down to us."

  • 4th General Council of the Lateran (1215)
    • 1 - Confession of Faith
      • "We firmly believe and simply confess that there is only one true God, eternal and immeasurable, almighty, unchangeable, incomprehensible and ineffable, Father, Son and holy Spirit, three persons but one absolutely simple essence, substance or nature."
      • "This holy Trinity, which is undivided according to its common essence but distinct according to the properties of its persons, gave the teaching of salvation to the human race through Moses and the holy prophets and his other servants, according to the most appropriate disposition of the times."

  • General Council of Florence (1431)
    • "Whoever wills to be saved, before all things it is necessary that he holds the catholic faith. Unless a person keeps this faith whole and undefiled, without doubt he shall perish eternally. The catholic faith is this, that we worship one God in the Trinity, and the Trinity in unity, neither confounding the persons nor dividing the substance. For there is one person of the Father, another of the Son, and another of the holy Spirit.But the Godhead of the Father, of the Son and of the holy Spirit is one, the glory equal, and the majesty co-eternal.
Fathers and Doctors of the Church Documents
  • De Fide (378) - Of Faith - Ambrose
    • "8. If, then, God is One, one is the name, one is the power, of the Trinity. Christ Himself, indeed, saith: "Go ye, baptize the nations in the name of the Father, and of the Son, and of the Holy Spirit." In the name, mark you, not in the names."
    • 9. Moreover, Christ Himself saith: "I and the Father are One." "One," said He, that there be no separation of power and nature; but again, "We are," that you may recognize Father and Son, forasmuch as the perfect Father is believed to have begotten the perfect Son, and the Father and the Son are One, not by confusion of Person, but by unity of nature."
    • "10. We say, then, that there is one God, not two or three Gods, this being the error into which the impious heresy of the Arians doth run with its blasphemies. For it says that there are three Gods, in that it divides the Godhead of the Trinity; whereas the Lord, in saying, "Go, baptize the nations in the name of the Father and of the Son and of the Holy Spirit," hath shown that the Trinity is of one power. We confess Father, Son, and Spirit, understanding in a perfect Trinity both fulness of Divinity and unity of power."

  • De Civitate Dei (Book 11) (426) - City of God - Augustine
    • Chapter 10: Of the Simple and Unchangeable Trinity, Father, Son, and Holy Ghost, One God, in Whom Substance and Quality are Identical.
      • "There is, accordingly, a good which is alone simple, and therefore alone unchangeable, and this is God. By this Good have all others been created, but not simple, and therefore not unchangeable. Created, I say—that is, made, not begotten. For that which is begotten of the simple Good is simple as itself, and the same as itself. These two we call the Father and the Son; and both together with the Holy Spirit are one God; and to this Spirit the epithet Holy is in Scripture, as it were, appropriated. And He is another than the Father and the Son, for He is neither the Father nor the Son. I say another, not another thing, because He is equally with them the simple Good, unchangeable and co-eternal. And this Trinity is one God; and none the less simple because a Trinity."

  • De Civitate Dei (Book 13) (426) - City of God - Augustine
    • Chapter 24: How We Must Understand that Breathing of God by Which The First Man Was Made a Living Soul, And that Also by Which the Lord Conveyed His Spirit to His Disciples When He Said, Receive the Holy Ghost.
      • "Wherefore, when our Lord breathed on His disciples, and said, Receive the Holy Ghost, He certainly wished it to be understood that the Holy Ghost was not only the Spirit of the Father, but of the only begotten Son Himself. For the same Spirit is, indeed, the Spirit of the Father and of the Son, making with them the trinity of Father, Son, and Spirit, not a creature, but the Creator. For neither was that material breath which proceeded from the mouth of His flesh the very substance and nature of the Holy Spirit, but rather the intimation, as I said, that the Holy Spirit was common to the Father and to the Son; for they have not each a separate Spirit, but both one and the same."

  • Summa Theologica - Most Holy Trinity (1265) - The Highest Study of God - Thomas Aquinas
    • "Whether the Son Is Other Than the Father?"
      • On the contrary, Augustine [*Fulgentius, De Fide ad Petrum i.] says: "There is one essence of the Father and Son and Holy Ghost, in which the Father is not one thing, the Son another, and the Holy Ghost another; although the Father is one person, the Son another, and the Holy Ghost another."
      • "Thus, to avoid the error of Arius we must shun the use of the terms diversity and difference in God, lest we take away the unity of essence: we may, however, use the term "distinction" on account of the relative opposition. Hence whenever we find terms of "diversity" or "difference" of Persons used in an authentic work, these terms of "diversity" or "difference" are taken to mean "distinction." But lest thesimplicity and singleness of the divine essence be taken away, the terms "separation" and "division," which belong to the parts of a whole, are to be avoided: and lest quality be taken away, we avoid the use of the term "disparity": and lest we remove similitude, we avoid the terms "alien" and "discrepant." For Ambrose says (De Fide i) that "in the Father and the Son there is no discrepancy, but one Godhead": and according to Hilary, as quoted above, "in God there is nothing alien, nothing separable."