Judaism was born and grew up in a world dominated by religions that taught that there were many, usually contending, divinities (polytheism) who manifested themselves in various natural phenomena such as sun, moon, storms, mountains, animals or even individual holy people (paganism) and who could inhabit or be represented by human made images such as statues or paintings (idolatry).
The Jewish Bible rejects all these beliefs, as does the Koran, and asserts that the One God who created the universe is not to be equated in any way with one of God’s creations. Thus there is a dual unbridgeable reality: the one uncreated God and God’s creation.
This chasm holds true even for spiritual entities like souls, angels, and Holy Scriptures that are closer to God than material things but are still not identical with the only One. Thus the Divine can never become incarnate in a person, place or text and worship directed to any person or object is idolatry.
The Hebrew Bible recognizes that other nations have other Gods and the requirement to worship the One imageless God applies only to the people of Israel, and anyone else who joins them. Thus the prophet Micah asserts that even in the Messianic Age “All peoples will walk, each in the name of its God.” (Micah 4:1-5)
Thus religious unity will not be the result of conformity to one universal religion, but will result from the harmony of many different religions, each following its own God, respecting other religions while disagreeing with them.
As the Koran says [5.48] “For every one of you did We appoint a law and a way. If Allah had wanted He could have made you one people, but (He didn’t) that He might test you in what He gave you. Therefore compete with one another to hasten to do virtuous deeds; for all return to Allah (for judgement), so He will let you know that in which you differed.”
Thus Judaism and Islam are pluralistic religions unlike Christianity and Buddhism where their own basic teaching is held to be universally necessary to achieve every individual’s salvation or personal enlightenment.
The Hebrew prophets teach that what is required of every human is to act justly, love mercy and to walk humbly with God (Micah 6:8). This humility means that we do not claim that our religious truth is a universal one that everybody else has to accept. There is a great deal of overlap in the moral and ethical teachings of the world’s religions even though they disagree on specific issues like abortion, eating meat or capital punishment.
Thus there are fundamental differences in theology and philosophy in the world’s religions even though they often have some similar customs, rituals or wisdom sayings. In a future life/world God will let us know the ultimate Divine reality; but in this life/world we can only know how just, loving, merciful and pluralistic we are.