hr_Noah_6Director Darren Aronofsky’s “Noah” is being touted as not your grandfather’s Bible movie. That’s true—but the film is also a quintessential example of the kind of biblical story you get, and the kind of biblical “hero” you get, in a secular culture that has lost all connection to what the story means.

Mr. Aronofsky’s Noah, played by Russell Crowe, isn’t merely a warts-and-all version of the “righteous man” from the Book of Genesis, who at God’s command builds an ark that saves his family, along with the world’s birds and beasts, from the flood that is God’s punishment of a human race that has grown corrupt. In Genesis, Noah has his faults, as when he shames himself in front of his sons by passing out drunk and naked after the flood has subsided and they have left the ark.

But Mr. Aronofsky’s Noah is a homicidal monster, part religious fanatic, part Zero Population Growth progenitor. In Mr. Aronofsky’s twist on the Bible, Noah is determined to exterminate his own offspring as well as the rest of mankind, all supposedly in God’s name.

This Noah ruthlessly abandons a young woman—the girlfriend of his teenage son—to be trampled to death by a mob. He then takes it upon himself to murder his newborn granddaughters in their mother’s arms. An all-is-forgiven ending, with Patti Smith singing “Mercy Is” on the soundtrack, does little to mitigate Noah’s general repulsiveness.

All filmmakers of biblical subjects take fictional liberties with their material—as do the makers of biblical plays, novels, operas, paintings and sculptures. Biblical narratives, as literary critic Erich Auerbach observed, are notoriously skimpy with information about their characters’ thoughts, feelings and motivations. Filmmakers step in to supply complex and often conflicted human beings—Judas, King David, among others—out of the bare outlines the Bible provides.

Like other adapters of Bible stories, Mr. Aronofsky has drawn on extra-biblical sources: the apocryphal Book of Enoch, in this case, and likely Gnostic texts that present the biblical God as evil. Throughout “Noah,” God is referred to simply as the “Creator”—a title that calls to mind the “demiurge,” the sinister lesser divinity who, according to the Gnostic cosmology, fashioned the material world.

The liberties that Mr. Aronofsky has taken, however, run counter to nearly every religious interpretation of Noah ever made, from the commentary by Philo of Alexandria, a Jewish contemporary of Jesus, to Dino de Laurentiis’s 1966 movie spectacle, “The Bible: In the Beginning,” with John Huston portraying Noah as a genial patriarch who swats the animals on their behinds to keep them moving into the ark.

In Philo’s view, and in the rabbinical writings that followed, the story of Noah signified God’s continued solicitude for the human race despite its past depravity, and his willingness to start afresh. In Genesis, Noah’s three sons are grown men with wives and, later, numerous children. God honors Noah by making a covenant never again to destroy the planet with water, offering the rainbow as a sign of that covenant.

In Jewish thought, Noah is a precursor to Abraham, another righteous man with whom God makes a covenant promising countless offspring. In Islam, Noah is one of the earliest prophets.

Early Christian writers used this theme of God’s reward for human faithfulness as an allegory of Christian salvation, with the window of the ark symbolizing the wound in Christ’s side from which had poured his redemptive blood. The story of Noah was thus an inspiring story of a world begun anew. It was a favorite theme of medieval mystery plays, which embellished the tale with humor: Noah’s wife was often portrayed as a comical battle-ax who had to be dragged into the ark by her husband and sons.

Benjamin Britten turned one of those plays into his 1957 opera, ” Noye’s Fludde.” Michaelangelo painted scenes from the Noah story onto the ceiling of the Sistine Chapel. Other artists—from Jan Breughel the Elder in the 17th century to the American primitivist Edward Hicks in the 19th and Salvador Dali in the 20th—delighted in portraying the ark and its pairs of animals.

It is the themes of faithfulness and optimism that give the biblical Noah story coherence. Without them you have—as with Mr. Aronofsky’s two-and-a-half-hour movie—a vast and dreary expanse of time, space and meaning to fill. The director strives his frenetic best. He gives us giant fantasy creatures that look like Transformers, except that they’re made of rocks. He gives us, as a substitute for religion, the creeds of animal rights and environmentalism, in which the gravest sins are eating meat and mining. He gives us knifings, arsons and impressive computer-generated battles.

But as a determined secularist in a determinedly secular world, he can’t give us the one thing that the Noah story once stood for: hope.

Ms. Allen is the author of “The Human Christ: The Search for the Historical Jesus” (Free Press, 1998).