Opinion by Jeffrey Weiss, Special to CNN

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(CNN) - Pope Francis surprised Israeli and Palestinian leaders last month when he invited them to a special prayer ceremony at the Vatican this Sunday - not least because religion has often been the source, not the salve, of the region's conflicts.

Still, Pope Francis offered his "home" - the Vatican - as the perfect place to plea for some divine assistance, and Israeli President Shimon Peres and Palestinian Authority President Mahmoud Abbas dutifully agreed to attend.

"The Pope has placed it in this perspective: Prayer is like a force for peace,” Vatican Secretary of State Archbishop Pietro Parolin told Vatican Radio.

"We hope that there, where human efforts have so far failed, the Lord offers to all the wisdom and fortitude to carry out a real peace plan."

But Sunday's special ceremony at the Vatican raises an interesting question: When Francis, Peres and Abbas bow their heads in prayer, will they be talking to the same God?

After all, Jews, Christians and Muslims all trace their faiths back to a fellow named Abraham, whom they all claim was chosen for special treatment by the Almighty.

Not academic

The “same God” question is one theologians have hammered at for as long as there have been enough religions for the query to make sense.

The question is hardly academic, though. In fact, a number of politicians, religious leaders and scholars have expressed hope in recent years that a convincing answer on the God question might dampen the violence committed in His name.

Yale Divinity School theologian Miroslav Volf recently edited a book titled “Do We Worship the Same God? Jews, Christians, and Muslims in Dialogue.”

In the introduction, Volf explained why the title question matters:

"To ask: ‘Do we have a common God?’ is, among other things, to worry: ‘Can we live together?’ That’s why whether or not a given community worships the same god as does another community has always been a crucial cultural and political question and not just a theological one."

On the other hand, there’s CNN Belief Blog contributor and Boston University religion professor Stephen Prothero.

His book on this subject is titled “God Is Not One: The Eight Rival Religions That Run The World.”

Prothero writes:

“For more than a generation we have followed scholars and sages down the rabbit hole into a fantasy world where all gods are one … In fact this naive theological groupthink – call it Godthink – has made the world more dangerous by blinding us to the clash of religions that threaten us worldwide.”

In the world of politics, President George W. Bush asserted the unity side of the argument more than once in the years after the 9/11 attacks - often as a way to deflect accusations that America was at war with Islam.

Bush told Al Arabiya television, “I believe there is a universal God. I believe the God that the Muslim prays to is the same God that I pray to. After all, we all came from Abraham. I believe in that universality.”

Pope Francis invites Israeli, Palestinian leaders to Vatican peace talks

Pope John Paul II drew from the same rhetorical well several times.

“We believe in the same God, the one God, the living God, the God who created the world and brings his creatures to their perfection,” he first said in a speech to Muslims in Morocco in 1985.

Looking for a more recent example? Consider the plight of Vatican envoy to Malaysia.

Shortly after he arrived there last year, Archbishop Joseph Marino said that is was fine by him that Christian translations of the Bible into Malay use the word “Allah” for “God.”

“Allah” is, of course, the Arabic word for God and is found in the Quran. The Christian translators explained that since most Malaysians are Muslim, it’s the word they’re most comfortable with and therefore the best choice for the translation.

But many Muslim authorities in Malaysia were furious. They say Christians are slipping in the familiar word as a way to convert Muslims. And conversion of Muslims is all but illegal in Malaysia.

There’s a lawsuit ongoing about the translations. Marino had to apologize for pushing into Malaysian politics.

Points of disagreement

So what do the “Abrahamic” religions disagree about?

Among other things: the purpose of humanity, the relationship of God and humanity, sin, forgiveness, salvation, the afterlife, Jesus, Muhammad, the calendar, and the religious importance of Abraham himself.

Plus the nature of God.

Any summary will leave out enormous nuance. Internal divisions within religions have fueled some of the worst examples of human violence. Consider the long and frequently bloody history of troubles between Catholics and Protestants or the growing death toll of Muslim-on-Muslim attacks.

But there are common elements about God widely accepted in each tradition.

Judaism

Start with Judaism, since it came first and established roots that carried into the other two.

Jewish tradition teaches that there is one and only one God, creator of everything, and He established physical and moral laws. As Judaism’s preeminent prayer says: “The Lord our God, the Lord is one.”

This God walks and talks directly with His creations – for a while.

Eventually, He chooses one particular nomad (Abraham) to father a mighty nation that God sets up as an example to other nations.

This God likes the smell of burning meat and demands other extremely specific physical offerings as evidence of obedience and repentance. And He gives His chosen people a particular set of laws – but doesn’t mind discussion and even argument about those laws.

A famous rabbinic saying implies that every word in Judaism’s sacred texts can be understood in 70 correct (but related) ways. And human reasoning can even trump divine intention. (No kidding. It’s in the Talmud)

This God judges His people every year. Tradition says he’s willing to accept imperfection, as long as it comes with repentance.

He’s big on obedience, not so much on faith. He’s not nearly as attentive to the behaviors of non-Jews. (There’s a famous Jewish joke with the punch line “Would you mind choosing somebody else once in a while?”)

Tradition holds that there’s a World To Come after death where moral accounts will somehow be settled. But this God is vague on details.

Christianity

The most obvious differences in the Christian God are the traditional teachings about the Trinity and Jesus. God is three separate persons who are also one. How? Christianity says the Trinity is a “mystery” of faith.

According to Christian tradition, God begets a son who is somehow also Him but not Him to atone for Original Sin. He sacrifices that son though a brutal death and thus achieves humanity's salvation.

But the son, who also is God, rises from the dead. And that sacrifice redeems eternally all who accept and believe in it. Faith, not behavior, is the essential measure of salvation.

This God is willing to vastly expand what it means to be among His “chosen people.” He’s also willing to cancel many of the laws that had applied to that chosen group for this expanded membership.

Orthodox Jews say that God prohibits them from eating a cheeseburger; Christians say God has no problem with them wolfing down Big Macs.

Unlike the Jewish God, whose instructions are almost all about this world, the Christian God is focused more on eternal salvation: heaven and hell.

Finally, for this God, much of the Jewish scriptures (which are all God’s word) are actually about foreshadowing Jesus. Including Abraham.

Islam

The Muslim God is a bit more like the Jewish God.

There is no Trinity in Muslim tradition. Jesus was a prophet, but no more divine than other prophets.

God has never has had anything like physical attributes and has no gender. (Some Muslim commentators say that the noun “Allah” is masculine, but only in the way that all nouns in some languages include gender.)

Muslim tradition holds that God wants one thing from humans: Submission. The word “Islam” is defined as “submission to the will of God.”

For Muslims, all true prophets in Jewish and Christian traditions were actually Muslim because they knew to submit correctly to God. Differences between Muslim, Jewish and Christian interpretations of God are due to errors that crept into the other two faiths, Islam teaches.

The Muslim God, like the other two, initially demanded that Abraham sacrifice a son. But the Muslim God wanted Abraham’s son Ishmael, not Isaac, who Jewish tradition holds was offered as a the sacrifice.

The Muslim God also designated, from before the world began, a perfect man to be his final prophet: Muhammad. God’s perfect truths are found only in the Quran and in the sayings of Muhammad, the hadiths.

And the Muslim God, like the Christian God but unlike the Jewish God, will welcome believers to paradise and condemn many non-Muslims - exactly which ones is a matter of much discussion - to eternal torment.

Final answer

So do Christians Muslims, and Jews, really all worship the same God?

In two major volumes on the subject recently published by scholars from various faiths and traditions, including Volf’s, the most inclusive response from these scholars is basically: Yes, and it’s our God.

This is not a new way of answering the question.

In 1076, Pope Gregory VII wrote this to a Muslim leader: “We believe in and confess one God, admittedly, in a different way…”

But like many other religious leaders on all sides of the argument, Gregory insisted that his version of the Almighty is the one whom the others are unknowingly and incompletely worshiping.

A less exclusivist set of religions might shrug off the differences. But all three claim to have the only “True Faith.”

So do all three faiths actually worship the same deity, whether they call him God or Allah or Adonai?

God only knows.

Jeffrey Weiss is an award-winning religion reporter in Dallas.The views expressed in this column belong to Weiss. A version of this story first ran in September 2013.

CNN's Daniel Burke contributed to this article.