Above all guard for me this great deposit of faith for which I live and fight, which I want to take with me as a companion, and which makes me bear all evils and despise all pleasures:
I mean the profession of faith in the Father and the Son and the Holy Spirit.
I entrust it to you today. By it I am soon going to plunge you into water and raise you up from it. I give it to you as the companion and patron of your whole life.
I give you but one divinity and power, existing one in three, and containing the three in a distinct way. Divinity without disparity of substance or nature, without superior degree that raises up or inferior degree that casts down… the infinite co-naturality of three infinites.
Each person considered in himself is entirely God… the three considered together… I have not even begun to think of unity when the Trinity bathes me in its splendor.
I have not even begun to think of the Trinity when unity grasps me.
~St. Gregory of Nazianzus (325-389) – A Doctor of the Church whose theological work continues to influence modern theologians.
Catholic Catechism, paragraph 256