Pope Clement IV (Latin: Clemens IV; 23 November 1190 – 29 November 1268), born Gui Foucois (Latin: Guido Falcodius; French: Guy de Foulques or Guy Foulques)[1] 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 Pope 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 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.