Q. When was the concept of the Holy Trinity first identified by the Catholic Church and is there biblical support for it?
A. First Identified Use of the Word Trinity
The word trias (of which the Latin trinitas is a translation) is first found in Theophilus of Antioch about A.D. 180. He speaks of “the Trinity of God [the Father], His Word and His Wisdom”. In the next century the word “Trinity” is in general use. The first creed in which it appears is that of Origen’s pupil, Gregory Thaumaturgus. In his Ekthesis tes pisteos composed between 260 and 270 he writes:

“There is therefore nothing created, nothing subject to another in the Trinity: nor is there anything that has been added as though it once had not existed, but had entered afterwards: therefore the Father has never been without the Son, nor the Son without the Spirit: and this same Trinity is immutable and unalterable forever.”

A good explanation of the Holy Trinity by Frank Sheed, a modern theologian is this:

In its barest outline, the doctrine contains four truths: (1) In the one divine Nature, there are three Persons, the Father, the Son and the Holy Ghost. (2) No one of the Persons is either of the others, each is wholly Himself. (3) The Father is God, the Son is God, the Holy Ghost is God. (4) They are not three Gods but one God.

Sheed, F. J. (2011-06-26). Theology for Beginners (p. 34). Angelico Press

Scriptural Support for the Holy Trinity
In Scripture there is no single term by which the Three Divine Persons are denoted together. One of the earliest references to the concept of more than one person in God was Genesis 1:26— Then God said, “Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth, and over all the creatures that move along the ground.” (Notice the plural pronouns “us” and “our” which denote more than one person.)

There are additional numerous scriptural references to the concept of the Holy Trinity as three persons but one God. Following are some, but not all, of those references.

• “Hear, O Israel! The LORD is our God, the LORD is one!” (Deut. 6:4)
• “I am the LORD, and there is no other; Besides Me there is no God.” (Isa. 45:5)
• There is no God but one. (1Cor. 8:4)
• And after being baptized, Jesus went up immediately from the water; and behold, the heavens were opened, and he saw the Spirit of
• God descending as a dove, and coming upon Him, and behold, a voice out of the heavens, saying, “This is My beloved Son, in whom I am well-pleased.” (Matt. 3:16-17)
• “Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit.” (Matt. 28:19)
• Jesus said: “I and the Father are one.” (John 10:30)
• “He who has seen Me has seen the Father.” (John 14:9)
• “He who beholds Me beholds the One who sent Me.” (John 12:45)
• If anyone does not have the Spirit of Christ, he does not belong to Him. (Rom. 8:9)
• “Joseph, son of David, do not be afraid to take Mary as your wife; for that which has been conceived in her is of the Holy Spirit.” (Matt. 1:20)
• And the angel answered and said to her [Mary], “The Holy Spirit will come upon you, and the power of the Most High will overshadoyou; and for that reason the holy offspring shall be called the Son of God.” (Luke 1:35)
• [Jesus speaking to His disciples] “And I will ask the Father, and He will give you another Helper, that He may be with you forever; the Spirit of truth, whom the world cannot receive, because it does not behold Him or know Him, but you know Him because He abides with you, and will be in you.” … “If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him, and make Our abode with him.” (John 14:16-17, 23)