1. The name: Trinity, meaning and history of:
No one is sure exactly when it was first used because some texts may have been lost. But the earliest surviving use of the term was by Theophilus of Antioch around 170 AD:
In like manner also the three days which were before the luminaries, are types of the Trinity [Τριάδος], of God, and His Word, and His wisdom. And the fourth is the type of man, who needs light, that so there may be God, the Word, wisdom, man [To Autolycus 2:15].
The name is from the Latin word trinitas, which means “three” or “triad.” The Greek equivalent is triados.
2. The Catechism on the Trinity and the place in our Faith:
The Church expresses her trinitarian faith by professing a belief in the oneness of God in whom there are three Persons: Father, Son, and Holy Spirit.
The three divine Persons are only one God because each of them equally possesses the fullness of the one and indivisible divine nature.
They are really distinct from each other by reason of the relations which place them in correspondence to each other.
The Father generates the Son; the Son is generated by the Father; the Holy Spirit proceeds from the Father and the Son [CCCC 48].
The central mystery of Christian faith and life is the mystery of the Most Blessed Trinity.
Christians are baptized in the name of the Father and of the Son and of the Holy Spirit [CCCC 44].
3. Proof of the Trinity:
God has left some traces of his trinitarian being in creation and in the Old Testament but his inmost being as the Holy Trinity is a mystery which is inaccessible to reason alone or even to Israel’s faith before the Incarnation of the Son of God and the sending of the Holy Spirit.
This mystery was revealed by Jesus Christ and it is the source of all the other mysteries [CCCC 45].
4. Proof that the Father is God, the Son is God and the Spirit is God:
Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort [2 Co. 1:3].
There is . . . one God and Father of us all, who is above all and through all and in all [Eph. 4:4-6].
In the beginning was the Word, and the Word was with God, and the Word was God.
And the Word became flesh and dwelt among us, full of grace and truth; we have beheld his glory, glory as of the only Son from the Father [Jn. 1:1, 14].
Then [Jesus] said to Thomas, “Put your finger here, and see my hands; and put out your hand, and place it in my side; do not be faithless, but believing.”
Thomas answered him, “My Lord and my God!” [Jn. 20:27-28].
While they were worshiping the Lord and fasting, the Holy Spirit said, “Set apart for me Barnabas and Saul for the work to which I have called them” [Acts 13:2].
But Peter said, “Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back part of the proceeds of the land? . . . You have not lied to men but to God” [Acts 5:3-4].
5. There are only 3 Persons in God: Father, Son, and Holy Spirit. We know about the persons from the words of Christ.
6. They possess equal Power and Majesty.
7. They are co-eternal, and have the same Nature.
8. God is in constant work inside and outside Him. (Work here means “Activity” not Labour)
9. The Work within (Called: OPERA AD INTRA) is Father eternally begetting the Son, and the two Spirating/breathing forth the Holy Spirit or the Holy Spirit proceeding from the Father and Son.
10. The Work outside (OPERA AD EXTRA) is summed up in: CREATION, REDEMPTION, and SANCTIFICATION.
11. The Persons act in perfect unity. Though there are some actions ascribed to PERSONS in God: e.g. the Father Creates, the Son Redeems, and the Holy Spirit Sanctifies. However, the Father does not create without his Son (WORD), the Son does not redeem without His Father, and the Holy Spirit does not sanctify without the Father and the Son.
12. The Action of the Blessed Trinity within is one of Great Power; Power born of Love and Unity. The overflow of this Love and Power gave birth to the three Exterior works of God (Opera Ad extra). God’s Opera ad intra, is the fount from whence flows everything good. God is Love himself, and so every action of God is rooted solely in love
13. The Mystery of the Blessed Trinity does not mean we CANNOT KNOW ANYTHING ABOUT THIS, it means we cannot understand PERFECTLY. For instance WE KNOW there are 3 Persons but cannot UNDERSTAND PERFECTLY what this means.
14. The Blessed Trinity is One in Nature, Power, Existence, Authority, Majesty, and EVERYTHING but their Personhood. They are One in all things but only DISTINCT (Do not use “Different”) in their Person. So, the Father, Son and Spirit are one, but not one and the same person.
This article is partly inspired by on by Jimmy Akin on National Catholic Register. The “General Points” section is from an old post we made on Facebook years back.