The painting that the chronicler Vasari describes is of course the famous School of Athens, which Raphael completed in 1509, just as Michelangelo was bringing the ceiling of the Sistine Chapel to life. It is a work that is full of clues to hidden reading. The figure of Plato, situated at the center of the composition, is in fact a faithful rendering of his revered Leonardo da Vinci. But Raphael also places himself in the scene. He is the figure gazing directly at the viewer from the right-hand side of the painting, next to Zoroaster, Ptolemy, and a group of astrologers. Raphael’s presence in the scene was not a secret, and was achieved, according to Vasari, “with the help of a looking-glass.”⁴ But Raphael added one more small mystery.⁵

Very close to where Raphael appears as an astrologer, we see Euclid,⁶ the great mathematician and father of geometry, though here Raphael gives him the face of his great mentor, Bramante. He is shown bent over a slate on which he demonstrates his theorems to a group of students. There, on the gold-edged neck of his tunic, incorporated within the design of the brocade, one can pick out four letters: RVSM.

Nowadays we know it to be the painter’s signature, and while it may not seem remarkable to us, at the time it was quite an act of daring. Why? Because no painter in the service of the church in the sixteenth century was permitted to sign his work. Not one. The ecclesiastical authorities whose job it was to commission work enforced this rule with a great zeal, claiming that it was to ensure that the artist not fall prey to the sin of pride.

The curious signature RVSM turned out to be simply an acronym for Raphaël Vrbinas Sua Manu ([Made by] the hand of Raphael Urbino). This discovery left me wondering. What did all this tell us about the great Raphael?

Suddenly, it became clear. The Pearl’s creator had an innate opposition to rules. He was a rebel. Someone who, for some reason that I now felt impelled to discover, liked to leave pathways to his ideas by the means he knew best—painting.