Jesus says, “I have much more to tell you, but you cannot bear it now. When he comes, however, being the Spirit of truth he will guide you to all truth. He will not speak on his own, but will speak only what he hears, and will announce to you the things to come. In doing this he will give glory to me, because he will have received from what he will announce to you. All that the Father has belongs to me. That is why I said that what he will announce to you he will have from me” (Jn.16:12-15).
In the Johannine Gospel passage, Jesus is the speaker. He is talking about the Holy Spirit. And then he speaks of the Father. Clearly, there are three persons, Jesus, Holy Spirit and Father, in this pericope. This Gospel today is the biblical basis of the Dogma of the Holy Trinity. The Catholic Church believes in One God but in Three Divine Persons.
The Trinity is difficult to understand. How is it that there is One but Three Gods? It seems to defy human logic. This Dogma is not born all at once. The philosophical-theological conception of Three Gods but One has developed over the centuries. It was finally approved in the Council of Nicea in 325 Common Era (CE).
Historically, before Nicea, or in pre-Nicene period, Philo of Alexandria (b.25 CE-d.?), a Jewish thinker, first conceives of “God, the One or Being whom he calls Father and of the Logos whom he calls Son” … and of the “Holy Spirit, of whom Philo also speaks” (Urban,1995,50).
In the second century, Ignatius of Antioch (110 CE), Shepherd of Hermas (115 CE) and Justin Martyr (150 CE) — all follow the view that the Father generated his creative Logos, which is present in Jesus, and the Holy Spirit, the inspirer and enlightener … (52).
In the beginning of the third century, Irenaeus of Lyons (200 CE) gives a creedal formula much like the Creed of Nicea. He says: “God the Father, not made, not material, invisible; one God the creator of all things … the Word of God, Son of God, Christ Jesus our Lord … the Holy Spirit through Whom the prophets prophesied …” (53).
For brevity, due to limited space here, let us go now to the Formula of the Creed. As completed in 325 CE, the Nicene Creed reads as follows:
“We believe in one God, the Father almighty, maker of all things, visible and invisible; and in one Lord Jesus Christ, the Son of God, the only begotten from the Father, that is, from the being (ousia) of the Father, God from God, Light from Light, true God from true God, begotten, not made, one in being (homoousios) with the Father, through whom all things were made, those in heaven and those on earth. For us men and for our salvation He came down, and became flesh, was made man, suffered, and rose again on the third day. He ascended to the heavens and shall come again to judge the living and the dead. And in the Holy Spirit” (ND #7).
The Creed, or Nicene Creed, read or recited every Sunday during the Mass is first completely formulated and approved in the Council of Nicea, in which The Holy Trinity is proclaimed as a Dogma of Faith. One cannot be a Catholic without accepting and proclaiming this Dogma.