The following theological points apply primarily to the Roman Catholic Church, the largest Christian denomination.
A. GOD AS THREE? ************************
The Catholic idea of Trinity breaks God into three separate beings: The Father, the Son and the Holy Ghost (Matthew 28:19).
Contrast this to the Shema, the basis of Jewish belief:
"Hear O Israel, the Lord our God, the Lord is ONE" (Deut. 6:4).
Jews declare the Shema every day, while writing it on doorposts (Mezuzah), and binding it to the hand and head (Tefillin).
This statement of God's One-ness is the first words a Jewish child is taught to say, and the last words uttered before a Jew dies.
In Jewish law, worship of a three-part god is considered idolatry -- one of the three cardinal sins that a Jew should rather give up his life than transgress.
This explains why during the Inquisitions and throughout history, Jews gave up their lives rather than convert.
B. MAN AS GOD? ******************
Roman Catholics believe that God came down to earth in human form, as Jesus said:
"I and the Father are one" (John 10:30).
Judaism says that the Messiah will be born of human parents, and possess normal physical attributes like other people. He will not be a demi-god, and will not possess supernatural qualities. In fact, an individual is alive in every generation with the capacity to step into the role of the Messiah. (see Maimonides - Laws of Kings 11:3)
