Three and a half billion people – more than half of the inhabitants of the Earth – trace their history and/or their faith to Abraham, an old man with an apparently barren wife who became patriarch of a great nation and demonstrated his faith with the near sacrifice of his son, Isaac.According to Jon Levenson, a professor of Jewish Studies at Harvard University, Abraham has served more “as a point of differentiation” among Jews, Christians, and Muslims than as “a node of commonality.”In Inheriting Abraham, Levenson draws on a close reading of the Book of Genesis and texts that are not part of the canon of Scripture in the three religious communities, in a learned, lucid and luminous examination of the distinctive character of Abraham in Judaism, which is best understood, he argues, through a comparison with the patriarch as he appears in “the authoritative literature” of the other two “Abrahamic traditions.” Jews, Christians, and Muslims revere Abraham, of course. And yet, Levenson points out, in the scriptures of all three religions, the “central action” takes place long after Abraham has come and gone.In Judaism, it occurs with God’s gift of the Torah to Moses on Mount Sinai (a covenant that, unlike the Abrahamic covenant, is conditional). For Christians it is the death, resurrection, and ascension of Jesus. And for Muslims it lies with God’s dictation to Muhammad of the Koran, the authoritative guide for human beings. Because believers believe that Abraham foreshadows these events, Levenson suggests, they emphasize different aspects of the Genesis narrative – and ignore others.The most important difference among those who draw on the Abrahamic traditions, Levenson claims, involves the meaning of God’s promise to Abraham’s “descendants.” For Jews, it applies to the progeny of Isaac, the son of Abraham and Sarah, and not to Ishmael, whose mother was Hagar. Those who fail to observe the commandments may be punished, but they can return to God’s favor through genuine repentance and atonement (especially on Yom Kippur).For Christians, the reference to “offspring” pointed the way to Jesus Christ, who in a sense supersedes Isaac and through the Crucifixion brings the blessing of Abraham to believers in God. Since paternity for them is a matter of behavior, born of faith and not of blood, and since in Genesis 12:3 (King James rendering) the Lord pledged that “in thee shall all families of the earth be blessed,” Christians can insist that Abraham, the man of faith, trumped Moses and that, thanks to Jesus, gentiles had “become, as it were, Jews.” In the Koran, Levenson notes, the son Abraham takes to be sacrificed is not named. Early Muslims split evenly between proponents of Isaac and those of Ishmael, and in subsequent centuries there was a pronounced shift toward the son of Hagar. For Muslims, the familial dimension and “chosen nation” are irrelevant to the story of Abraham, who is treated as a faithful, obedient and monotheistic prophet, a prefiguration of Muhammad – and the worthiest people are those who follow the one to the other.These distinctions, Levenson maintains forcefully, should not be confused with the distorting dichotomy, repeated over the centuries, that Jews are tribal and inward-looking while Christians are outward- looking, inclusive and universalistic.Abraham, he indicates, was often deemed “the first of the converts” and serves as inspiration (and a connecting link) to anyone who chooses to become a Jew. Nor is election in the Hebrew Bible the same as salvation in the New Testament.People outside the covenant, Levenson asserts, “are not outside the care and concern of God.”Equally important, far from embracing a natural undifferentiated humanity as an ideal, Christians stress the importance of baptism. They reject the universal Adamic identity, which they associate with a sin-infected human essence, Levenson indicates, in favor of an Abrahamic identity in which individuals attain righteousness in the sight of God based on their faith.By Maimonides’s time, Levenson observes, Jews had overcome the paucity of evidence in Genesis about Abraham’s beliefs and behavior and transformed him into a founder as well as a father, a prophet of the one true God and the keeper of commandments that would not be codified until Moses came down from Mount Sinai. Although Christians and Muslims also cast him in these two roles, Levenson concludes that Abraham has not bridged and cannot bridge communal boundaries because none of the three religions believes that the other two are legitimately Abrahamic.Levenson takes no risk in predicting that a neutral Abraham, “who is beyond text, beyond tradition, and beyond history,” isn’t likely to emerge. And, it seems to me, we shouldn’t want him to. As Inheriting Abraham illustrates, the common origins of Judaism, Christianity and Islam are sources not only of violent disputes but of profound insights into human nature.The writer is the Thomas and Dorothy Litwin Professor of American Studies at Cornell University.