Pietro Riario (1445 - 1474), was a son of Paolo and Pope Sixtus IVs' sister, Bianca Della Rovere. Sixtus IV, who nominated him in 1471 a bishop of Treviso and cardinal, archbishop of Florence in 1473. He was a humanist known for his patronage of literature and the arts. Sixtus IV, born Francesco della Rovere (July 21, 1414 – August 12, 1484) was Pope from 1471 to 1484. ... Humanism is a broad category of active ethical philosophies that affirm the dignity and worth of all people, based on the ability to determine right and wrong by appeal to universal human qualities—particularly rationalism. ...