On the Holy Trinity (Gregory of Nyssa) To Eustathius. All you who study medicine have, one may say, humanity for your profession: and I think that one who preferred your science to all the serious pursuits of life would form the proper judgment, and not miss the right decision, if it be true that life, the most valued of all things, is a thing to be shunned, and full of pain, if it may not be had with health, and health your art supplies. But in your own case the science is in a notable degree of double efficacy; you enlarge for yourself the bounds of its humanity, since you do not limit the benefit of your art to men's bodies, but take thought also for the cure of troubles of the mind. I may say that those who conceived this causeless hatred for us seemed to be acting very much on the principle of Æsop's fable. Well, what is their charge? But our argument in reply to this is ready and clear.
What, then, is our doctrine? The New Theological Movement. TheCatholicThing.org. Fr. Robert Barron's Word On Fire - Fr. Barron comments on Ross Douthat's "Bad Religion" The Trinity. The doctrine of the Trinity is encapsulated in Matthew 28:19, where Jesus instructs the apostles: "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit.
" The parallelism of the Father, the Son, and the Spirit is not unique to Matthew’s Gospel, but appears elsewhere in the New Testament (e.g., 2 Cor. 13:14, Heb. 9:14), as well as in the writings of the earliest Christians, who clearly understood them in the sense that we do today—that the Father, the Son, and the Spirit are three divine persons who are one divine being (God). The Didache "After the foregoing instructions, baptize in the name of the Father, and of the Son, and of the Holy Spirit, in living [running] water. . . . If you have neither, pour water three times on the head, in the name of the Father, and of the Son, and of the Holy Spirit" (Didache 7:1 [A.D. 70]).
Ignatius of Antioch Justin Martyr Theophilus of Antioch Irenaeus Tertullian Origen Hippolytus Novatian.