It is well known that Islam and Judaism reject the Christian faith that God is three persons. What is less known are the objections to that faith.
Ibn Taymiyyah (d. AD 1328) set out a number of objections in the 14th century. One interesting objection he makes is that the New Testament does not teach the Trinity. You cannot find the words “The Trinity” on any page of the New or Old Testaments.
That is true. However, most Christians, and most Jews as well, believe that one can state the words of God’s revelation in other words, at least sometimes, even though care is required. Thus, if the New Testament teaches that the Son is also God and that the Holy Spirit is God, and that there is only one God, then the New Testament teaches the Holy Trinity. The “Holy Trinity” would be a way of concisely summing up the New Testament teaching on God in himself.
Well, this is what the New Testament does teach. For instance, “In the beginning was the Word, and the Word was with (the) God, and the Word was God” Jn 1:1. This amazing text “destroys all heresies” as Leo the Great teaches. Here, we see both a differentiation between the Word and the God, and also an identity between the Word and God. Since the Gospel is true, and since truth cannot contradict truth, we must find a way to reconcile this tension. The Tradition, guided by the Spirit, teaches us: The differentiation indicates we are dealing with two persons, the Word and the God; the identity indicates we are dealing with one nature or essence.