The claim that Christianity is not monotheistic would engender the longest most useless monologue from any Christian-with-a-capital-C or Christian theologian So don’t claim that. Unless you have the patience. The Creed has always been: credo in unum Deum.
But it is a mistake to equate that with the groundbreaking monotheism of the Jews: in those early times the Jews were absolutely unique among all the polytheistic religions, because of this single god, with an unpronounceable name. The thigh is : that is true monotheism.
Jesus’ words caused a great panic among the Jews, when he said, unequivocally, that he was God. Actually that alone would not have precluded monotheism. The problem was, he went on to talk about Abba, his Father-God, exactly as the Jews did. So, this presented a conundrum – a logical impossible duality. Of course, when he then finally introduced one more wrinkle, the Holy Spirt, he stuck the logical world, including the Christian faith that ensued, with a long explanation, which still confuses people today.
Let me apologize for my first paragraph. In no way is my intent to dismiss those who, in their devotion to the understanding of the mysteries of faith, have created the explanation of “three-in-one”. I only seek to admonish them, with love, to open their minds to a grander possibility.
In fact, the actual words of Jesus went far beyond three. He told us that we are all a part of one body, his body, the body of God. So, instead of three-in-one is should be All-in-One. I take that expression from Dr. Bronner, an Essene, maker of the soap that appears in all health-conscious stores. Read the bottle some time!
So, it is actually much better than monotheism , and beyond the simplicity of polytheism. Actually – and here is more heresy – it is very thoroughly explained in the Vedanta: that there is no separation between the individual and the universe. That’s a poor explanation of one of the deepest theologies known, but the idea is key: that we are all one and that One is what we call God.