St. Athanasius is said to have written the Athanasius Creed, which is the most profound explanation of the Church’s teaching on the Holy Trinity. It states:
And the Catholic Faith is this, that we worship one God in Trinity and Trinity in Unity. Neither confounding the Persons, nor dividing the Substance. For there is one Person of the Father, another of the Son, and another of the Holy Ghost. But the Godhead of the Father, of the Son and of the Holy Ghost is all One, the Glory Equal, the Majesty Co-Eternal. Such as the Father is, such is the Son, and such is the Holy Ghost. The Father Uncreate, the Son Uncreate, and the Holy Ghost Uncreate. The Father Incomprehensible, the Son Incomprehensible, and the Holy Ghost Incomprehensible. The Father Eternal, the Son Eternal, and the Holy Ghost Eternal and yet they are not Three Eternals but One Eternal. Read more here.St. Athanasius died in 373 and was declared a Doctor of the Church.
St Gregory Nazianzen, a contemporary and fellow Doctor of the Church, once wrote of him, "When I praise Athanasius, virtue itself is my theme: for I name every virtue as often as I mention him who was possessed of all virtues. He was the true pillar of the Church. His life and conduct were the rule of bishops, and his doctrine the rule of the orthodox faith."
St. Athanasius of Alexandria pray for us…