We Christians are monotheists, meaning we believe in one God. This is a belief we share with Jews and Moslems, as well as some other religious systems. However, there is a big difference. We say God is one but also three. God is one, but the Son and the Spirit are also God. For Jews and Moslems this is either nonsense or blasphemy, and they often claim that we are polytheists. However, we are simply being faithful to God’s revelation to us as expressed in the Old and New testament.
Others, even some Christians, would say that this belief in the Trinity is a result of pagan religion or philosophy influencing the simple message of love of God and neighbor. In other words, the fatherhood of God and the brotherhood of man. Still other critics will say that this belief was imposed on the Church by power-hungry bishops or emperors, but once again we say that we are being faithful to the one God who as revealed Himself to us as Trinity.
It is true that we don’t find the word “Trinity” in the New Testament. However, we certainly see the lived reality of the Trinity in the New Testament. For example, in St. Paul’s second letter to the Corinthians he writes: “The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” (2 Cor 13:14) as a blessing at the end of the letter. We see quite clearly the persone of the Trinity here. Or at Christ’s baptism:
“And when Jesus was baptized, he went up immediately from the water, and behold, the heavens were opened, and he saw the Spirit of God descending like a dove, and alighting on him; and lo, a voice from heaven, saying, “This is my beloved Son, with whom I am well pleased.” (Mt 3:16-17)
Here again we see the Father, the Son and the Holy Spirit revealing themselves. Or at the Transfiguration:
“And after six days Jesus took with him Peter and James and John his brother and led them up a high mountain apart. And he was transfigured before them, and his face shone like the sun, and his garments became white as light. And behold, there appeared to them Moses and Eli’jah, talking with him. And Peter said to Jesus, “Lord, it is well that we are here; if you wish, I will make three booths here, one for you and one for Moses and one for Eli’jah.” He was still speaking, when lo, a bright cloud overshadowed them, and a voice from the cloud said, “This is my beloved Son, with whom I am well pleased; listen to him.” (Mt 17:1-5)
The Father speaks, the Son is transfigured, and the Holy Spirit is there dazzling light surrounding Christ’s person and overshadowing the whole mountain. Finally, at the end of St. Matthew’s Gospel Christ says:
“And Jesus came and said to them, “All authority in heaven and on earth has been given to me. 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, teaching them to observe all that I have commanded you; and lo, I am with you always, to the close of the age.” (Mt 28:18-20)
Here, after the resurrection, Christ is telling the disciples that the belief in the Holy Trinity is the basis of Christian faith. So, we Christians believe that the New Testament clearly teaches the doctrine of the Trinity.
But what about the Old Testament? Certainly, when the Jews read the Bible they could not find any mention of the Trinity here, and frankly the Jews consider this interpretation of the Bible to be totally wrong. Now it has to be said that the Trinity is not present in the Old Testament. However, from the earliest days of the Church the Christians found hints about the Trinity even in the Old Testament. And we must remember that when the Apostles went out to preach, the only Bible they had was the Old Testament and they found the Trinity in that book.