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A Brief Introduction to the Blessed Trinity

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(Last Updated:  04 Jan 2002 )

The objective of this page is to provide an explanatory introduction to the doctrine of the Blessed Trinity.   The fact that God is three persons in one nature is the central mystery of the Christian faith, but it can be very hard to understand or explain.  This article may be a little disjointed, as it is based on the outline for a presentation I did on the subject.  It draws heavily from Frank Sheed's exposition on the matter in his excellent book Theology and Sanity.  At the end of the article I provide some links for further reading.
Through this article, please bear in mind that "the Trinity" is not some dry theological doctrine, but represents the interior life of God Himself, and since He has gone to the trouble of revealing some of this interior life to us, we ought to do our best to try to understand it as much as we can.

Trinity in Scripture:

[Note that this is a very superficial treatment of what we see of the Trinity in Sacred Scripture.  See the list of further reading below for links to much more detailed treatements of this matter.]

Matthew 28:19 - "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,"

When demonstrating the Trinity there are four points to establish:

1. The Father is God
1 Corinthians 1:3 - "Grace to you and peace from God our Father and the Lord Jesus Christ."

2.  The Son is God
John 20:28 - "Thomas answered him, "My Lord and my God!""
Hebrews 1:8 - "But of the Son he says, "Thy throne, O God, is for ever and ever, the righteous scepter is the scepter of thy kingdom."

3.  The Holy Spirit is God
Acts 5:3-4 - "But Peter said, 'Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back part of the proceeds of the land? 4 While it remained unsold, did it not remain your own? And after it was sold, was it not at your disposal? How is it that you have contrived this deed in your heart? You have not lied to men but to God.'"
2 Corinthians 3:17-18 - "Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 18 And we all, with unveiled face, beholding the glory of the Lord, are being changed into his likeness from one degree of glory to another; for this comes from the Lord who is the Spirit."

4.  There are not three Gods, but one God
Deuteronomy 6:4-5 - "Hear, O Israel: The Lord our God is one Lord; 5 and you shall love the Lord your God with all your heart, and with all your soul, and with all your might." (Note that in the NT, Jesus says the same thing in Mark 12:29).
Isaiah 43:10-11 - "'You are my witnesses,' says the Lord, "and my servant whom I have chosen, that you may know and believe me and understand that I am He.  Before me no god was formed, nor shall there be any after me. 11 I, I am the Lord, and besides me there is no savior.'"

For a bit more about Jesus and his role in the Godhead, have a look at these passages:
Philippians 2:5-11; Colossians 1:15-20; John 17:3-5.

How Can We Explain the Trinity?
It's a mystery, the greatest mystery of our faith, but that doesn't mean we can't explore it.  Some people think a mystery of the faith is like a museum with a big brick wall in front of it so that we will never know what is inside.  Really it is like a museum that we are welcome to wander around in as much as we like, but there are an infinite number of exhibits so we will never finish learning what there is to know.  It is important that we make the effort to have a look around though, because it is important to know God as he is.  That's what we will be doing in heaven (1 John 3:2 - "Beloved, we are Gods children now; it does not yet appear what we shall be, but we know that when he appears we shall be like him, for we shall see him as he is").

If we want to get close to God we should try to know him personally, not just by what he does (Creator, Redeemer, Sanctifier is one way to put it), but by who he is (Father, Son and Holy Spirit).

Here are the basics of the doctrine of the Trinity:
1. In the one divine nature, there are three persons, the Father, the Son, and the Holy Spirit.
2. No one of the persons is either of the others, each is wholly himself.
3. The Father is God, the Son is God, the Holy Spirit is God.
4. They are not three Gods but one God.

Some Background - God is Existence
A key truth about God's nature is that He is existence.  Everything in the universe is dependent upon something else for its existence.  We each have the possibility of not existing.  But for anything to exist at all, there must be something that is not dependent on something else for existence.  This something is God.  God cannot not-exist; God is existence.  Figuring this out was one of the greatest achievements of the Greek philosophers of the 5th century BC.  But a good thousand years before that, the Jews knew it too - but only because God told them:
God said to Moses, "I AM WHO I AM." And he said, "Say this to the people of Israel, I AM has sent me to you." (Ex 3:14).

Some More Background: Person and Nature
We have to be able to distinguish between person and nature.  Put simply, our nature determines what we are; person describes who we are.

The Trinity is a Revealed Doctrine
God is a pure spirit, and a better understanding of the Trinity comes from thinking about the fact that it is God's nature to exist, and about the actions of spirit: knowing and loving.  We should also remember that the inner life of God is not something we could have figured out for ourselves apart from Revelation.

The Second Person
Perhaps the biggest clue is found at the start of John's Gospel: "In the beginning was the Word, and the Word was with God, and the Word was God".  Now, God is pure spirit, so a word produced by God would be more like a thought or an idea.  So what idea produced in God's mind could possibly be God?  The idea that God has of himself.

When God thinks of himself, this thought must be perfect, because God is perfect, so whatever is in the Father must be in this idea of himself, and must be exactly the same as it is in himself.  Otherwise God would have an inadequate idea of himself, which wouldn't make sense.

Here's how Frank Sheed puts it:

The next step is really important: the Father knows and loves, so his idea of himself knows and loves.  In other words, the idea is a person.  The thinker and the thought are distinct, but they are of the same nature.  The idea, or word, of God, is the Son.  God has always been thinking, so he has always been Fathering the eternal Son.

So the Second Person proceeds from the First by way of a word, or by way of knowledge.  The other primary operation of a pure spirit is love.

The Third Person
Between the two infinite persons of the Father and the Son, there is an infinite love.  Since in their mutual love they give everything they have, then the love between them is perfect, so that love produces an eternal person as well, the Holy Spirit.

Again, here's how Sheed puts it:

So one way to think of the three persons of the Trinity is as Existence in the Person of the Father, as Knowledge in the person of the Son, as Lovingness in the Person of the Holy Spirit.  Or you can think of the nature of God as perfect Thinker, perfect Idea or Word, and perfect Love.  The inner life of the Trinity consists of the infinite interflow of knowing and loving among three persons who have the same nature and are one God.

That's enough for now, I think.  There's a whole lot to try and get your head around when you think about the Trinity.

Further Reading

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