Liz Lev, an art historian at Duquesne University in Rome, says the authors are focusing too closely on the details and missing the big picture.
"If we stop looking for secret hidden meaning … [the 'Creation of Adam' panel] is showing us probably the most inspiring image of what it means to be a human being. We see an activation of the potential of man."
How about the fresco of Adam, Eve and the serpent in the garden? Most depictions of the Garden of Eden show an apple tree, but not on the Sistine ceiling. Blech and Doliner believe Michelangelo was inspired by Jewish texts that say the forbidden fruit is actually a fig.
"I think this is one of these powerful proofs that not only did Michelangelo know Jewish texts, but he felt it important to incorporate the ideas of these texts into some of these frescoes," said Blech.
Perhaps Michelangelo was inspired by another artist. Almost a century before Michelangelo finished the ceiling, another great fresco painter named Masolino da Panicale painted Adam and Eve beneath a fig tree in the Brancacci chapel in Michelangelo's hometown Florence.
Schuyler found a different reference to Jewish mysticism in the temptation panel and published her findings in an article titled "Michelangelo's Serpent With Two Tails." She believes the serpent is really Lilith, Adam's first wife. She points out that Adam and this female serpent look like twins, which is how Lilith is described in Kabbalah.
The authors take Michelangelo's purported interest in Jewish tradition one step further and claim that Michelangelo painted the figures from the Old Testament to urge the church to embrace the Jewish community.
A cleaning of the frescoes in the 1980s revealed details that had been obscured for centuries. Doliner and Blech believe that some are secret messages. They point to the yellow circle on Aminidab, who Christians believe is an ancestor of Christ.
"This is one of the most important indications of Michelangelo's true feelings about the Jews, and a major idea he wanted to get across throughout the entire chapel," said Blech.
The yellow marking is also known as the badge of shame, which Jews were required to wear by law. It dates back 300 years before Michelangelo's day, and can be likened to the yellow Star of David from Nazi Germany.
The authors interpret this image as a condemnation of the church's attitude toward the Jewish community. Doliner says the artist was asking: "This is one of the ancestors of Christ, the Lord of your religion. And this is how you treat the people of your Lord?"
Other experts, such as Barbara Wisch, an art historian at SUNY Cortland, believe that Michelangelo was simply echoing the anti-Semitism of his day and that he painted the badge of shame on Aminidab to mark him as an outsider.
Wisch acknowledges that it is hard to know exactly how Michelangelo felt about the Jews because he rarely mentioned them in his writing, but said, "By marking one ancestor with the contemporary Jewish badge, it's as if time is telescoped and he is marked as being a Jew, with all the stereotypes and evil, wicked connotations that go with being a Jew."