Today we celebrate the feast of the Most Holy Trinity. There is a book by lay Catholic theologian, Frank Sheed, called Theology and Sanity. Early in the book, Sheed gives a very thorough explanation of the doctrine of the Trinity, which has been touted as one of the best explanations available. If you have a mind for philosophy or want to dive deeper into the doctrine, it is well worth the read, but I will summarize his essential points.

The doctrine of the Trinity is something the Church refers to as “a mystery.” We must first understand how the Church defines mystery, which is slightly different from the secular definition. A mystery is something about God which we cannot fully understand, but that does not mean that we cannot know something about it. God wants to be known and loved, so He reveals certain things about Himself to us so that we may understand Him as much as our human limits will allow. We will not understand Him in His fullness until we get to heaven. While here on Earth, we see the mystery with eyes of faith, which allows us to believe completely in the mystery, while still knowing we have limited and finite knowledge regarding it.

God has revealed to us that He is Triune – three persons in one God. Sheed begins his analysis by explaining what we mean by nature and person. Most simply, a person has a nature, but a nature does not have a person. “Nature answers the question of what we are; person answers the question of who we are” (pg. 92). Everything has a nature, but not everything is a person. So, for example, you know the nature of a table – what makes it a table – but you would not ask a table who it is. Similarly, our nature is the source of what makes us a person and is the source of our actions, but our nature does not perform actions; we perform actions. So, there is a distinction between what we are (nature) and who we are (person).

Our human natures are finite, but God’s divine nature is infinite and possessed by three distinct persons. They do not share their infinite nature since sharing implies division. Rather each person of the Trinity possesses the divine infinite nature wholly within His own distinct self. “The Father possesses the whole nature of God as His Own, the Son possesses the whole nature of God as His Own, the Holy Spirit possesses the whole nature of God as His own” (pg. 97). Since nature tells us what something is, then each member of the Trinity is fully God in His own distinct personhood. So, why do we call them one God instead of three gods? Think of three men. The first man cannot think with the second man’s mind. The second man cannot feel with the third man’s heart. While they have similar human natures – what makes them human – there are differences in their persons that make them each unique to themselves. The three persons in God, however, each fully possess the identical same divine nature and can, therefore, each do all the things that have to do with being God.

After explaining how God is three persons with one nature, Sheed moves on to discuss the relationship between the three persons. He tells us that the second person of the Trinity is referred to by two terms: Son and Word. Human language is limited, but God is not. So, each of these words tell us something that is true about Jesus that is lacking in the other word. The term Son tells us that Jesus receives God’s nature from His Father the same way the son of a man is a man. However, we again run into problems with our limited human language. God is infinite and eternal and therefore does not exist in time – though Jesus, in His human nature, did. God is omnipresent. We humans speak in past, present, and future tense. So, it is important to note that there was not a specific point in time when the second person was created and received the divine nature, rather the two have always been. Secondly, Jesus is referred to as the Word of God. Since God the Father is a pure spirit, He does not speak vocal words with a physical body, so His Word is more like a thought or an idea. “It is only God’s revelation that tells us what reason never could, that God, knowing Himself with infinite power, conceives an idea of Himself” (pg. 103). Since God is complete, His idea of Himself is also complete, so both the first and second persons of the Trinity are complete, infinite, and equal, yet distinct from one another.

The third person of the Trinity is the Holy Spirit, who proceeds from the first and the second. The first and the second person, knowing themselves fully, generate a lovingness from that perfect knowledge. All of the terms used to describe the Holy Spirit convey movement, such as wind, breath, and fire. So, this love generated by the Father and Son moves through creation as the Spirit. Again, we find that our limited language boxes the generation of the love into time, however the Council of Florence (1438-45) defined that “the Holy Spirit is from the Father and the Son eternally, and has His essence and subsistence from Father and Son together, and proceeds eternally from both as from one principle and one single spiration.” Together, the Father and the Son breathe the Holy Spirit.

God desires for us to participate in the divine life of the Trinity, which is a continual spiral of knowledge and love of God. “If anyone loves me, he will keep my word, and my Father will love him, and we will come to him and will make our abode with him” (John 14:23). This is precisely what heaven is – our souls being absorbed into the Trinitarian life of knowledge and love of God. Here on Earth, our participation is finite and is subject to human limitations. In heaven, we will be able to participate fully as we see God for who He is, face to face.

To receive articles and reflections like these directly to your inbox, please subscribe.