Pope Clement IV, born Gui Foucois and also known as Guy le Gros, was bishop of Le Puy, archbishop of Narbonne, cardinal of Sabina, and head of the Catholic Church from 5 February 1265 until his death. His election as pope occurred at a conclave held at Perugia that lasted four months while cardinals argued over whether to call in Charles I of Anjou, the youngest brother of Louis IX of France, to carry on the papal war against the Hohenstaufens. Pope Clement was a patron of Thomas Aquinas and of Roger Bacon, encouraging Bacon in the writing of his Opus Majus, which included important treatises on optics and the scientific method.