(Canto 13, line 58)
This is Pier della Vigna (c. 1190- 1249), jurist and poet of the Sicilian school. He was of a modest family background and studied law in Bologna. In 1221, he was employed as a secretary to Emperor Frederick II. From 1230 he became one of Frederick's favorites and from 1246 prothonotary and royal governor in Sicily. He was by now one of Frederick's most trusted advisers. About the two keys, ancient commentator Buti explained that one is for consenting, that is to open, the other for denying, that is to close. Compare also Isaiah 22:22 for keys as symbols of power. In 1248, after Frederick's defeats at Parma and Bologna, Pier started losing his trust, and in 1249, he was suspected of a coup (but may have been innocent), was arrested in Cremona and thrown in jail at Santa Miniato al Tedesco, where both of his eyes were blinded with irons. The same year he committed suicide in prison - according to one account this occurred in Pisa.