Bacon was born near Ilchester in Somerset. His family appears to have been well-off, but, during the stormy reign of Henry III of England, their property was despoiled and several members of the family were driven into exile.
Roger Bacon studied at Oxford, lectured on Aristotle and later became a Franciscan friar and a professor at Oxford. He probably took orders in 1233, and crossed over to France to study at the university of Paris, then the centre of intellectual life in Europe. The two great orders, Franciscans and Dominicans, were not long-established, and had begun to take the lead in theological discussion. Alexander of Hales led the Franciscans, while the rival order rejoiced in Albertus Magnus and Thomas Aquinas. Bacon's abilities were soon recognised, and he enjoyed the friendship of such eminent men as Adam de Marisco and Robert Grosseteste, bishop of Lincoln. In the course of his teaching and research, he performed and described various experiments.
The scientific training Bacon had received, mainly from the study of the Arab writers, showed him the defects in existing academic debate. Aristotle was known only through poor translations; none of the professors would learn Greek. The same was true of Scripture. Physical science was not carried out by experiment in the Aristotelian way, but by arguments based on tradition. Bacon withdrew from the scholastic routine and devoted himself to languages and experimental research. The only teacher whom he respected was a certain Petrus de Maharncuria Picardus, or "of Picardie", probably identical with a certain mathematician, Petrus Peregrinus of Picardie, who is perhaps the author of a MS. treatise, De Magnete, contained in the Bibliotheque Imperiale at Paris. The contrast between the obscurity of such a man and the fame enjoyed by the fluent young doctors roused Bacon's indignation. In the Opus Minus and Opus Tertium he pours forth a violent tirade against Alexander of Hales, and another professor, who, he says, acquired his learning by teaching others, and adopted a dogmatic tone, which caused him to be received at Paris with applause as the equal of Aristotle, Avicenna, or Averroes.
Bacon met the Cardinal Guy le Gros de Foulques, who became interested in his ideas and asked him to produce a comprehensive treatise. Bacon, being constrained by a rule of the Franciscan order against publishing works out of the order without special permission, initially hesitated. The cardinal became Pope Clement IV and urged Bacon to ignore the prohibition and write the book in secret. Bacon complied and sent his work, the Opus Majus, to the pope in 1267. It was followed in the same year by the Opus Minus, a summary of the main thoughts from the first work. In 1268, he sent a third work, the Opus Tertium to the pope, who died the same year. Bacon fell out of favor, and was in fact later imprisoned by the Franciscan order, presumably because of some of his controversial teachings and aggressive style.
In his writings, Bacon calls for a reform of theological study. Less emphasis should be placed on minor philosophical distinctions as in scholasticism, but instead the bible itself should return to the center of attention and theologians should thoroughly study the languages in which their original sources were composed. He was fluent in several languages and lamented the corruption of the holy texts and the works of the Greek philosophers by numerous mistranslations and misinterpretations. Furthermore, he urged all theologians to study all sciences closely, and to add them to the normal university curriculum.
He rejected the blind following of prior authorities, both in theological and scientific study. His Opus Majus contains treatments of mathematics and optics, alchemy and the manufacture of gunpowder, the positions and sizes of the celestial bodies, and anticipates later inventions such as microscopes, telescopes, spectacles, flying machines and steam ships. Bacon studied astrology and believed that the celestial bodies had an influence on the fate and mind of humans. He also wrote a criticism of the Julian calendar which was then still in use.
He was intimately acquainted with the philosophical and scientific insights of the Arabic world, which was the most advanced civilization at the time. He was an enthusiastic proponent and practician of the experimental method of acquiring knowledge about the world. He planned to publish a comprehensive encyclopedia, but only fragments ever appeared.