“And when Jesus was baptised, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, “This is my beloved Son, with whom I am well pleased.”” (Matthew 3:16–17)
“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,” (Matthew 28:19)
“The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” (2 Corinthians 13:14)
“For through him we both have access in one Spirit to the Father. So then you are no longer strangers and aliens, but you are fellow citizens with the saints and members of the household of God,” (Ephesians 2:18–19)
The distinctive belief of Christianity is that God is a Trinity: one in essence and three in persons. Turn to Islam or to Judaism and you find a denial of this, and discover Jesus is either a prophet (Islam) or an executed blasphemer (Judaism). Christianity alone claims deity for Christ, and holds to a concept of the one God which allows for that one God to also be three persons. “That’s logical impossible” you might cry. “We know” would be the answer from two millennia of theologians.
So how did we get here? How did we get to the place where we hold to something we know passes all understanding? The simple answer is that in the Bible we find Jesus spoken of in terms which can only be used of God. He is put alongside the Father and the Spirit. He is called the Son of God. He forgives sins, and can both lay down his life at the crucifixion and take it up again at Easter. He stills storms, and shows mastery over creation.
For the first Christians, flabbergasted at what they saw, they no doubt thought back to those times in the Old Testament where God appeared to his people. They might have dwelt on the fact that in Genesis 1 we read “let us make man in our image”.
This doctrine of the Trinity, then, was not the result of speculation or theologians talking late into the evening. It was a result of reading the Scriptures, and making sense of what was seen. Again and again in the Old Testament the “word of the LORD” came to the prophets, and in one instance the word of the LORD came to Abram and “he brought him outside and said...” (Genesis 15:5). How could a word take someone outside? Well, the Apostle John realised that this “word” took flesh and dwelt among us (John 1:1-14). The New Testament simply clarified what was in the old. Jesus was seen in the ancient pages, and was understood to be God.
As our heads gently swim, perhaps I might put it this way: we believe in the Trinity, because the Father acts like God, Jesus acts like God and the Spirit acts like God. Yet we know that God is One (Deuteronomy 6:4). Quite how it works, we leave to God. That it works is clear in the pages of the Bible.