To speak on the Christian understanding of the Trinitarian nature of God is not a small task.
Any attempt to summarise or “put it in a nutshell” will always be inadequate.
The fact that the word “Trinity” (a somewhat technical term, in my opinion) does not exist in the old or new testament adds to the difficulty of this subject, and alienates those who cannot go beyond that fact.
Combine this with the clear Jewish teaching from the Old testament, that there is only one God, and everything now seems weak and suspicious, even to some professing Christians.
But, to be truly Christian in faith, we must believe in the Father, the Son and the Holy Spirit.
The Christian God, whom we love, trust and obey, is one God, and He is Father, Son and Spirit.
The disciples (Peter, James, John etc.) in the gospels, had no problem believing Jesus was a man, a real man, and then in faith to believe he was God’s chosen, anointed one, the promised son of David, the true prophet like Moses, and the Lamb who takes away the sin of the world, but to believe that Jesus is God’s son, and is God, is the step of faith that required eye witnesses of the resurrection, and direct teaching from eye witnesses.
Hence the importance of Thomas’s insistence on touching the wounds of the risen Jesus, and his proclamation “my Lord and my God”. As well, the start of John’s Gospel “In the beginning was the word, and the word was with God and the word WAS God. (The word became flesh and dwelt among us, therefore Jesus was the word and WAS God)
So now we have a Father and a Son. If the Son is God, and the Father is God, then we already have two persons and one God. But the New testament also goes on to declare the Holy Spirit is the Spirit of God, and the Spirit is God.
2 Corinthians 3:17 (NIV) Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom.
So, very briefly, I have shown a small number of verses that attribute deity to Father, Son and Holy Spirit. There are many other verses.
The Father, Son and Holy Spirit are referred to together in a number of verses, for example at the end of Matthew’s Gospel Jesus commands his disciples to baptise us in the name of the Father and of the Son and of the Holy Spirit.
Because 'three persons yet one God' is such a confronting truth, the early church included that understanding in the earliest “creeds”. Creeds were not prayers, but rather should be considered statements of faith, even as bare minimum statements of faith, or as, “non-negotiables”. If you look at the apostle’s creed, for example, the Trinitarian understanding of God is there.
The Apostles' Creed
I believe in God, the Father almighty,
creator of heaven and earth.
I believe in Jesus Christ, his only Son, our Lord,
who was conceived by the Holy Spirit,
born of the Virgin Mary,
suffered under Pontius Pilate,
was crucified, died, and was buried;
he descended to the dead.
On the third day he rose again;
he ascended into heaven,
he is seated at the right hand of the Father,
and he will come to judge the living and the dead.
I believe in the Holy Spirit,
the holy catholic Church,
the communion of saints,
the forgiveness of sins,
the resurrection of the body,
and the life everlasting.
How we “mathematically” or “logically” explain or fail to explain this understanding does not make or break this truth.
Black holes and relativity existed well before we knew they existed, and certainly before we could ever explain them.
But suggesting that God is some sort of theoretical complex equation to be nutted out by gifted minds would reduce God to something less than He is. He is certainly far beyond us, and any understanding we have is completely subject to his willingness to reveal himself to us.
His revelation is what determines our understating. In other words, believing in Father, Son and Holy Spirit, three persons, one God, is what we have been given by him, in his coming to us as Son, Jesus, who taught us about the Holy Father, and promised us his Holy Spirit.
We believe this because God has revealed himself this way.
The word “trinity” is simply a word we have given to summarise our Christian understanding of this revelation.
Some people find comfort in some easier explanations such as water being present as ice, steam and liquid, three states, one chemical. Some talk of each human being made up of body, mind and spirit, but I do not think this is at all a satisfactory understanding.
Personally, I find it easier to look at a husband and wife.
God uses marriage to make two separate people one body.
In the perfect marriage, the husband and wife are truly one in purpose and will.
To know the wife, is to also know the husband, so unified are they in this perfect marriage. Of course the only perfect marriage is Christ and the church, but here is another mysterious truth of Christianity which I will side step for now.
And if there is no actual comparison or model, in all creation, of "trinity" (which in reality there is not) that also does not disprove the truth of God being a Triune God. God, in actual fact, has nothing to be compared to, he is above and beyond his creation, all we have is what he reveals, and he has revealed himself as Father Son and Holy Spirit.
In my understanding of trinity, I certainly believe that the Father, Son and Spirit, are in perfect unity regarding all of the Father’s will, plan and purpose for all creation, for all eternity, and that, to me, redefines the understanding of one God. Notice I have put the Father as first in this order of three Person’s, one God.
Add to this a rich understanding of the loving perfect unity of Father, Son and Spirit: how the Father honour’s the Son, and the Son (Jesus) honours his Father, and how the Father and the Son honour the Holy Spirit, all serving one another and also serving and graciously ruling over all creation, and over all history, being one in plan and purpose to bring creation to its ultimate goal (another topic). And we too are greatly blessed and encouraged in our lives as individuals, but also as members of families, and members of church families, and members of God’s family, and participants in God’s ultimate and perfect plan for all creation.
But whether or not I can understand the Trinitarian nature of God, or whether it “suits me” or not, I am still left with the eyewitness accounts of the gospels and the strong teachings of the new testament, as well as the consistent teaching of the early church fathers who put together the creeds.
So, I actively choose to align myself, as a Christian, to this teaching and understanding, and my spirit and my conscience are at peace. I encourage all who profess to love Jesus, to believe that God is one, Father, Son and Holy Spirit. Amen