I want to start by underlining the greatness and the complexity of this subject.
Greatness, because there is no other subject in the entire universe that demands and deserves our attention, our reflection, than God himself. To begin to scratch the surface of what God is like is to taste the stuff that eternal life is made of. It is therefore desperately sad that too often we neglect this important aspect of what God is like. And I hold my hand up as someone very guilty of not giving this the thought it deserves, not emphasising it in my daily life as I should.
This greatness brings with it Complexity. When we look at this matter we are gazing into the very nature, the make-up of God himself. If this God made the vast universe that mega-brains like Stephen Hawking have to spend their whole lives trying to fathom, no wonder there are things we can't understand and fathom about this God himself. Loose ends we can't tie, and nor should we. The only way we can know anything about God is by what he has revealed about himself. So, I make some apologies that this has to be short (even shorter now), but in another sense I make no apologies for remaining silent on answering questions about which God himself has also kept silent.
The word "Trinity" doesn't appear in the Bible, but the truth it describes is all over the Bible. It means tri-unity. Three in one. It's all about God's "three-in-oneness".
What do we mean by saying that God is three in one?
Appropriately, there are three very clear things that the Bible teaches about this, three things we must believe and if necessary hold in (apparent) tension when we're getting to grips with God being three in one.
God is three persons, the Bible makes it very clear in numerous places. God the Father, God the Son and God the Holy Spirit.
But are these perhaps just different names for the one person? Is it that sometimes God is called Father, sometimes Son, Sometimes Spirit, depending on what he's doing or how he's acting? No, God is three persons, that is, three distinct persons:
God the Father is not God the Son, nor is he God the Holy Spirit.
God the Son is not God the Father, nor is he God the Spirit.
God the Spirit is not God the Father, nor is he God the Son.
We see this in several ways. Read especially John's Gospel. In the Bible we find the Son talking to the Father, the Father sending the Son, the Sons ending the Spirit. They act distinctly and relate to one another as distinct persons.
The Father is fully God. That is obvious from all over the Bible.
The Son also is fully God. John 1:1 talking of the Son says:
In the beginning was the Word, and the Word was with God, and the Word was God.
Do you notice? He is distinct (with God) but also fully God himself (the word was God).
Likewise the Spirit is fully God. There are many places were this is obvious. Here's one:
For who knows a person's thoughts except the spirit of that person, which is in him? So also no one comprehends the thoughts of God except the Spirit of God.
1 Corinthians 2:11
Just like the spirit of a person knows what they're thinking, so does the Spirit of God. The Holy Spirit is as much God as your spirit is you. One and the same.
Each person is fully God. And so we cannot accept any teaching that tries to say that any one person of the Godhead is somehow less God than the others. There are some versions of 'Christianity' that teach that the Son is not fully God, he was created to be a part of God, or a vehicle for God to show himself in. And the same with the Spirit, some say that he isn't God but is just the best of all the created beings. To hold a biblical picture of God we must believe that the Father, the Son and the Holy Spirit are each full God.
If we were just left with just these two first statements then we'd have an easy solution to this supposed mystery of the trinity. Three persons. Each God. Easy. Three Gods.
However, the Bible doesn't allow for Tri-theism, but for one God who is trinity, tri-unity. That's where point three is really crucial. There are three distinct persons, each fully God, and…
'I am the LORD, and there is no other, besides me there is no God'
One God and one God only, who does not share his glory with other minor gods. One God who demands our worship and our honour, our attention, our lives. One God who can save us. One God who will judge us.
That is, the three persons of the Godhead are distinct persons but they are one being.
And it is here that all illustrations to try and explain this break down, all analogies have their danger, because none are able to perfectly display this amazing reality. The three-in-oneness of God. One God, three persons.
So, as Matthew 28:19 says (emphasis added):
'Go therefore and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit'.
As I finish, a final thought or two.
If we neglect this truth, this doctrine, if we fail to emphasise and teach and love this reality of what God is like, we will eventually open the door to the many false versions of Christianity, who all fall down on this issue of the three-in-oneness of God.
By neglect and under-emphasis we risk losing something that Christians have died for, one of the most wonderful mysteries that Christ allows us to have a glimpse of, if not in our generation then the next one.
And also, our vision of God himself will remain far to small and puny, too domesticated and neatly packaged, defined by our wisdom and not his word.
In the Bible God's three-in-oneness is often explained in terms of how each person is at work in history and in people's lives to rescue and change sinners like us. God's three-in-oneness as revealed to us in the Bible is a cause for awe and wonder and joy and worship. Let's not lose that or take it for granted.