Pope Clement IV (d. 1268)
Pope Clement IV (Latin: Clemens IV; c. 23 November 1190 – 29 November 1268), born Gui Foucois (Latin: Guido Falcodius; French: Guy de Foulques or Guy Foulques) and also known as Guy le Gros (French for "Guy the Fat"; Italian: Guido il Grosso), was bishop of Le Puy (1257–1260), archbishop of Narbonne (1259–1261), cardinal of Sabina (1261–1265), 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.