Of all the works Leonardo da Vinci left posterity, only one has been recognized as a self-portrait: a red chalk drawing showing a fierce, lion-headed old patriarch with a furrowed brow and burning eyes. Last week an Italian artist and scholar by the name of Lorenzo Ferri insisted that he had found a second. The face of the Apostle Thaddeus, he said, second from the right in Leonardo's famed Last Supper* is none other than that of the painter himself.
A resemblance between Leonardo and the apostle first struck Ferri in 1937, when he painted a reproduction of the Last Supper for...