St. Peter Damian, a man of vehemence in all his actions who was brought up in the hard school of poverty, found that he had the vocation of a reformer. He exercised it in the first place against himself as one of the hermits of Fontavellana in about 1035, but he did not remain for long hidden in his cell: his colleagues soon made him their abbot (1043). In 1057, Stephen IX made him Cardinal Bishop of Ostia. By his preaching and writings he was one of the valuable collaborators of the eleventh century popes in their great work of reform. Pope Leo XII declared him a Doctor of the Church in 1823. His feast is celebrated on February 23 according to the Extraordinary Form of the Roman Rite.