“Trinitas Unitas” (Latin) = “three in One” = “three persons in One God” and “Unitas Trinitas” = One God in three persons”. (from the Athanasian Creed, developed in the west though the Latin theology of Tertullian and Augustine. more below)
The doctrine of the Trinity began with Scriptural verses and content.
1. The first truth is that there is only One God. (Mark 12:29, Deut. 6:4-5; 1 Timothy 2:5; 1 Corinthians 8:6; Isaiah chapters 40-48)
2. Secondly, there are texts which show us there are three persons in the One God: The Father, the Son, and the Holy Spirit.
Matthew 28:19 – “baptizing them in the name of the Father, and the Son, and the Holy Spirit”
2 Corinthians 13:14 – “The love of God” (the Father), & “the grace of our Lord Jesus Christ, & “the fellowship of the Holy Spirit”
Matthew 3:16-17 (voice of the Father from heaven, the Holy Spirit coming down in the form of a dove, Jesus Christ the eternal Son of God being baptized.)
1 Peter 1:2 [ “foreknowledge of God the Father”, & “sanctifying work of the Spirit”, & “to obey Jesus Christ” (The Son)]
Ephesians 4:4-6 (“one Spirit”, & “One Lord”, & “One God and Father”)
I Corinthians 12:4-6 (“same Spirit”, & “same Lord” & “same God”)
3. Thirdly, there are passages that clearly teach the Deity of Christ:
Mark 14:60-64; Matthew 2:1-12; Luke 1:34-35; John 1:1-5; 1:14, 5:17-18; 8:24; 8:56-58; 10:30-38; 18:1-6; 19:1-7; 20:28; Hebrews 1:3, 6, 8; Colossians 1:15-20; Philippians 2:5-8; Romans 9:5; and many others. (see more verses in the books recommended below.)
4. Fourthly, there are clear verses in Scripture that show that there is a personal relationship and interaction between the persons in the Trinity, and this is the reason for the “person” category. (“The Father loves the Son”, “the Father sends the Son”, “The Son loves the Father”, “the Father sends the Son”; “the Spirit testifies to the Son”, “do not grieve the Holy Spirit”; “the Son prays to the Father”; etc. The Greeks called this concept “hypostasis” (‘υποστασις ) [the Cappodocian fathers * see about hypostasis below] and in Latin it was “persona”.
* “The Cappadocians worked to bring these semi-Arians back to the orthodox cause. In their writings they made extensive use of the (now orthodox) formula “one substance (ousia) in three persons (hypostaseis)”.”
5. Fifth: there are clear verses on the Deity of the Holy Spirit: Genesis 1:2; Acts 5:3-5
So in church history, the doctrine of the Trinity was “fleshed out” by wrestling with all these verses together in a harmonized way that does not contradict one another.
In the first video below –
Todd Friel of “Wretched TV/radio” takes the hilarious video of Lutheran Satire on the Trinity and breaks it down.
“Trinitas Unitas” (Latin) = “three in One” = “three persons in One God” and “Unitas Trinitas” = One God in three persons” (Latin word “trinitas” to describe the three persons from Matthew 28:19, 2 Corinthians 13:14, Matthew 3:16-17 is first used by Theophilus of Antioch, 180 AD; developed more by Tertullian 200 AD, developed further by Augustine (died in 430 AD), Athanasian Creed (5th or Sixth Century).
The Athanasian Creed: “The most likely time frame is in the late fifth or early sixth century AD – at least 100 years after Athanasius. The theology of the creed is firmly rooted in the Augustinian tradition, using exact terminology of Augustine’s On the Trinity(published 415 AD).”
It is very important to help others understand the distinction between nature/substance/essence vs. person; and that these are 2 different categories.
Some good books that are helpful in getting a grasp on the doctrine of the Trinity: