Greek Trinity

The Christian doctrine of Holy Trinity comes not from the bible, but from the development of the religion in the third and forth centuries AD. A notable influence was the school of Neoplatonism founded by Plotinus, who held that the cosmos emerged from the One, the Intelligence, and the Soul. The influential Christian bishop, Synesius of Cyrene, was a devoted student of the great neoplatonist Hypatia of Alexandria. It is thought that Synesius did not live long enough to hear of her gruesome death at the hands of a Christian mob. In a hymn, he writes:

I sing to Thee, Unity, I sing to Thee, Trinity;
Thou art One being Three, art Three being One;
and the intelligible segment holds what has been divided still indivisible.