The Catchism of the Catholic Church affirms that in their worship of Allah, Muslims “together with us…adore the one, merciful God, mankind's judge on the last day” (paragraph 841, citing the Lumen Gentium of 1964). This is somewhat at odds with the views that current Pope Benedict expressed of Islam in his 2006 Regensburg lecture. Since that time, and the furor his words provoked all over the planet, the Pope/theologian has scrubbed his analysis.

It is certainly tempting, and maybe a normal reaction, to equate the Allah of Islam with the Jehovah of the Jewish and Christian Scriptures. After all, both personalities are single God-Creators who hold providential control over all. This alone makes the comparison substantial at first blush. As far as I can tell that is good enough for most—and the question is settled. The “God” of Christianity and “Allah” of Islam must be the same. Any differences are…sectarian quibbling.

Really? Are Christianity and Islam really that similar? Does history bear that out? When I consider the cultures spawned by each faith I see a huge clash of worldviews. I see huge differences between Moses and Mohammed, or Jesus and Mohammed. More than that, after the first blush has passed, it appears that the definitions behind the titles reveal very different entities. Below are 10 contrasts between Allah and the Jehovah of the Old and New Testaments. I refer where I can to statements in the Qur’an.

1. Allah has no essential nature by which he acts: what he does is good because he does it. Jehovah is essentially good: he does what he does because it is his nature to do good and not evil. (see Sura 6:12).
2. Allah weighs the good deeds against the bad, Jehovah demands total holiness. (Sura 11:114…the good deeds cancel out bad ones; overlooks evil deeds for martyrs, 3:195).
3. Allah looks for external compliance (confession), Jehovah looks for a change of heart. Verses in the Koran that speak of salvation emphasize “good deeds” (5:9, 7:42, 18:30). Islam is not about “knowing God” but about compliance to him (“islam” means “submission”).
4. Allah has not revealed himself in any personal way, but only has revealed his will. Of the 99 names for Allah, none is personal, none is “Father.” Jehovah is revealed to be known in the Christian Scriptures, and is called Father.
5. The name “Allah” is not found in the Christian Bible. Muslims claim that “Allah” is not just a generic name for God, but is his personal name. This is at odds with God’s claim in Exodus 3, but also striking since the word “Allah” never occurs in the Old or New Testaments.
6. The names “Yahweh” and “Elohim” are not found in the Koran. But Yahweh is the personal name by which God identified himself (Ex. 3).
7. Allah is not associated with Jerusalem in the Koran as Yahweh is in the Old Testament. It is the “City of David” by which Jehovah would send his promised one (messiah). It is the Zion often mentioned throughout the Old Testament. None of these designations find their way into the Koran. In fact, the Koran never mentions Jerusalem, yet Muslims claim it as their holy city.
8. Allah does not make any promises to Israel, but Jehovah promises the land (Palestine) to his people Israel.
9. Allah is not called the God of chosen Israel, as he is in the Bible. In the Koran the Jew and Christian are to be rejected (Sura 5:51). His name “The God of Abraham, Isaac, and Jacob” is the name he said he would be remembered by for all generations (Ex. 3:15)—but this title is not associated with Allah in the Koran. Remember that “Jacob” is later called “Israel” by God.
10. Allah never personally reveals himself, Jehovah has. Jehovah is known because he became a man and revealed himself. Allah is only known by description (the deeds he has done). He has no knowable essence or character. In Christianity we know both who God is and what we are because God has revealed himself. Christ is the exact image of God. This very idea is Islam’s greatest sin—but it is the greatest truth of Christian theology. The most important ideas of each faith distinguish them from each other.

True, Allah and Jehovah are both described as maximal creator-Gods. But the problem with equating them just because they are in the same theistic category is to fail to recognize one feature of their descriptions: they are persons.  If I describe Bob with all of the characteristics of John—it is true that I have described two men (right category), but I have failed at the level of identity. It does not follow that Allah and Jehovah are identical just because they are both maximal creator-Gods.

Theoretically, the idea of Allah and Jehovah could both be wrong. But they cannot both be right. And they cannot be one in the same.