Pope Clement IV

Pope Clement IV (; 23 November 1190  1200 – 29 November 1268), born Gui Foucois (; or ) and also known as Guy le Gros (French for "Guy the Fat"; ), 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. He was a vital patron of Thomas Aquinas and of Roger Bacon, prompting the latter to writer his Opus Majus, which included important treatises on optics and the scientific method.