The Holy Trinity is the most important mystery of our Catholic faith. Why? The Holy Trinity is the mystery of God Himself. When we ask questions like “Who is God?” or “What is God?”, the answer is “The Holy Trinity.” But for most of us, that doesn’t answer the question. It just gives us even more questions. The reason we so often get that answer, though, is because even after 2000 years, the Holy Trinity is still a mystery.

So, what is the Holy Trinity? The Athanasian Creed can help us begin to understand this mystery of our faith. The Athanasian Creed is nearly as old as the Nicene Creed. Many Catholics don’t know about it, though, because we don’t regularly say it at Mass. Another source that we can turn to is St. Thomas Aquinas’s Summa theologiae, but it can be challenging to understand for someone who hasn’t spent a lot of time reading philosophy. I will do my best to use these two works to help shine some light on the mystery of the Holy Trinity.

First, we believe that there is one, and only one, God. Second, we believe that in God, there are three distinct persons: the Father, the Son, and the Holy Spirit. Third, we believe that each of the three persons is equal in infinity, in power, in glory, in majesty, and in eternity. This means that we believe that the Father is God, the Son is God, and the Holy Spirit is God, but that there is only one God, not three.

If this is the case, then what is the difference between the three persons? Why is it not three Fathers, three Sons, or three Holy Spirits? This is the part that can get complicated. The Father is “the unbegotten.” This means that He has no source, no origin. The Son is “the begotten.” This means that his origin is in the Father, but it does not imply that He was made or created. There was never a time that the Son did not exist. He is eternal, just like the Father. The Holy Spirit is the one who “proceeds from the Father and the Son.” This means that He comes from the Father, but not in the same way as the Son.

St. Thomas Aquinas tries to explain this in a number of ways, but the simplest for me to grasp is to say that there are two “processions” in God. One of these processions has a name, “the Word”, who is the begotten Son of the Father. The other is called the “procession of love”, who is the Holy Spirit. The Word is the Image of the Father, who reveals the Father and shows us the path back to Him. The Holy Spirit is the Love of the Father through the Son extended to us, who seeks to move our wills toward the Father and the Son.

If all of this gives you a headache, then all you need to know is this: there is one God who is Father, Son and Holy Spirit. This is the Holy Trinity. Athanasius writes, “the Catholic Faith is this: that we worship one God in Trinity, and Trinity in Unity.”

Fr. Matt