Bacon, Roger (between 1214 and 1220?–1292)

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(between 1214 and 1220?1292)

Roger Bacon, English philosopher and scientist, known as Doctor Mirabilis, was probably born between 1214 and 1220 and died in 1292, probably at Oxford. Bacon wrote in 1267 that he had learned the alphabet some forty years before and that his once wealthy brother had been ruined by his support of King Henry III during the barons' revolt. He studied arts at Oxford and then at Paris, where as regent master (c. 1237) he was among the first to lecture on the forbidden books of Aristotle when the ban was lifted. Here he wrote his Summa Grammatica, Summulae Dialectices, Summa de Sophismatibus et Distinctionibus, his Quaestiones on Aristotle's Physics, Metaphysics, and De Sensu et Sensibili, and on the pseudo-Aristotelian De Plantis and Liber de Causis ; he also wrote commentaries, now lost, on De Anima, De Generatione et Corruptione, De Caelo et Mundo, and De Animalibus.

These early lectures reveal a philosopher, immature but of unusual ability, conversant with the new literature of Aristotle and his Arabic commentators. They are of some historical interest, since Bacon was representative of the new breed of masters at Paris who prided themselves on being pure Aristotelians. In fact, however, like Avicenna and Gundissalinus before them, they were still strongly influenced by other traditions (especially Neoplatonism) that dominated such apocryphal works as the Liber de Causis and, in Bacon's case, the popular Secret of Secrets. This latter work, thought to be Aristotle's esoteric instructions to Alexander the Great, is a study in kingcraft which, in addition to advocating a sound, practical philosophy, gives much astrological advice and hints at the magical virtues of herbs and gems and the occult properties of numbers. From his glosses on the book, it seems that Bacon was most impressed by its vision of a universal science of great practical import that included all the secrets of nature. This unified science, revealed by God to the Hebrews, who passed it on through the Chaldeans and Egyptians to Aristotle, was concealed in figurative and enigmatic language but might be rediscovered by one morally worthy and mentally qualified to receive it. Where the pagans failed, Bacon held, a Christian might succeed. Therefore, around 1247 he left Paris, where he had been pursuing a mastership in theology, and returned to Oxford, where Adam Marsh, Robert Grosseteste's Franciscan associate, introduced him to that great man's work. For two decades, Bacon writes, he studied languages and the sciences, training assistants, cultivating the fellowship of savants, and spending more than £2,000 on "secret books," instruments, and tables.

Sometime during the latter half of this period he must have joined the Franciscans, to whom Grosseteste bequeathed his library. Neither his impoverished brother nor the mendicant friars could provide the experimental equipment Bacon longed to have; nor did the majority of the friars share his views on the importance of his work. Resenting the preference shown to the more orthodox theologians, Bacon became embittered and vented his spite in cutting and often unjust criticisms of some of the best minds of the age. Worse, his childlike credulity with regard to the apocalyptic literature of the times led him to side with the extremist followers of Joachim of Floris. This made his views suspect; he was sent to Paris and forbidden to circulate his writings outside the order. But Pope Clement IV, learning of Bacon's proposed encyclopedia of unified science in the service of theology and unaware that the work was largely in the planning stage, wrote for a secret copy on June 22, 1266. Hoping for papal aid to complete the project, Bacon, in the short space of eighteen months, composed as a preliminary draft his Opus Maius (synopsized and implemented by the Opus Minus and Opus Tertium, the latter rich in biographical detail). With the Opus Maius, Bacon sent the pope a copy of his Multiplicatio Specierum, a concave lens "made at great expense," and "a precious map of the world." Unfortunately, Clement died in November 1268, before the last of the opera arrived.

Bacon probably returned to Oxford; he completed his Communia Mathematica and Communia Naturalium (two of his most mature works) and wrote Greek and Hebrew grammars and his Compendium Studii Philosophiae. The last, intended as a general introduction to his principal writings, degenerated into an emotional diatribe against the evils of the age; these were, according to Bacon, especially manifest in the universities where the two teaching orders (Dominicans and Franciscans) were neglecting his favorite subjects. It also revealed a revival of Joachite interests (Bacon referred to the ridicule his "logical proof" of the imminence of the Antichrist provoked among the friars).

According to the Chronicle of the Twenty-four Generals, written in 1370, the Franciscan minister general, Jerome of Ascoli (later Pope Nicholas IV), imprisoned him for "suspected novelties." This account has been questioned, primarily because nothing could be found in Bacon's scientific or astrological views that had not been endorsed by many reputable theologians of the day, such as Albertus Magnus. More likely, it was a political move to silence the irascible friar, whose caustic views on the morals of the secular masters would do little to ease the strained relations between them and the friars (whose orthodoxy had been seriously compromised by the fanatical Joachite fringe). At any rate, Bacon's confinement could hardly have been rigorous or long enough to inhibit his penchant for frank expression; in 1292 he was writing in the Compendium Studii Theologiae on his favorite topics with all his old verve and biting invective. He died, however, before this work was completed.


The strength and the weakness of Bacon's erratic genius are nowhere more apparent than in the Opus Maius, his most characteristic and distinctive work. Both a plea and a plan for educational reform along the study lines pursued by Bacon himself, it is divided into seven partsthe causes of error, philosophy, the study of languages, mathematics, optics, experimental science, and moral philosophy. The first part descries four barriers blocking the road to truth: submission to unworthy authority (for example, crediting living theologians with a prestige due only to the Church Fathers or the Scriptures), the influence of custom, popular prejudice, and concealment of one's ignorance with a technical show of wisdom. Although by far the greatest portion of the book is devoted to mathematics, optics, and moral philosophy (to which, Bacon claimed, all speculative science should be ordered), Bacon's fame until recently rested on this first part and the relatively short section on experimental science. The belief that experimental science was the keystone of Bacon's reform was in part based on the misleading evidence of Samuel Jebb's 1733 edition of the Opus Maius, which omitted Part VII. By scientia experimentalis, however, Bacon meant any knowledge through experience as opposed to inferential or reasoned knowledge. When he said that nothing can be known with certainty without experience, his use of the term experience was twofold. One aspect of experience is based on sense perception and is called human or philosophical; the other aspect is interior and is derived from an illumination of the mind by God (whom Bacon identified with Aristotle's agent intellect). Thus, although sense perception is necessary to knowledge, certainty cannot be attained without divine illumination. Interior experience admits of seven degrees, beginning with that required for certitude in mathematics or the natural sciences and culminating in such mystical or ecstatic states as St. Paul's vision of heaven.

Bacon devoted the most attention, however, to what humans can know about the wonders of nature by sense perception and the first degree of illumination. From the examples cited in Part VI and throughout the work, Bacon seems to have been less an original experimenter and more a propagandist for scientists such as Peter of Maricourt. His contributions to scientific theory, like his empirical research, were confined largely to optics. With the aid of new source material from Alhazen and Abū-Yūsuf Yaʿqūb ibn Ishāq al-Kindī, he was able to develop significantly many of Grosseteste's views concerning the tides, heat, and double refraction and to give the most mature expression to Grosseteste's theory that light (and all physical force generally) is transmitted in pulses like sound waves. Since this "multiplication of species" requires a medium, Bacon argued, the transmission cannot be instantaneous, even though the time interval is imperceptible. His application of the theory to vision and the working of the eye was one of the most important studies done on this subject during the Middle Ages and became the point of departure for developments in the seventeenth century. Bacon seems to have surpassed his teachers both in his knowledge of convex lenses and parabolic mirrors and in his ability to foresee such applications of science as automobiles, motorboats, and aircraft.

If, by continuing the Oxford tradition begun by Grosseteste, Bacon was in advance of his contemporaries, he was also incredibly naive in some of his other views. His uncritical acceptance of what others claimed to have observed is often in violation of his own canons for avoiding error. Much of his stress on the importance of language studies came from his conviction that all knowledge can be found in the Scriptures and "secret books," whose full meaning God reveals by interior illumination only to those whose lives are pure. He held that because of men's sins, God's scientific revelations were obscured by errorswhich is one reason for testing empirically what the ancient sages say. Bacon seems to have had little use for abstract reasoning or speculation for its own sake. His interest in mathematics and logic, like his interest in astrology and alchemy, was purely practical. If all physical force, like light, is propagated rectilinearly, it is subject to geometric analysis. This, together with his conviction that the movement of the planets influences all terrestrial events except free will itself, was his reason for thinking that mathematics is the key to all natural sciences.

Not only was his faith in astrology unwarranted, but his ideas of theology belonged to a bygone age. Even prior to 1250, the Paris Franciscans, impressed by the Euclidean-Aristotelian ideal of a deductive science, were exploring how far the concepts of theology might be analyzed with greater logical rigor and theological propositions formalized in terms of axioms (first principles of reason and philosophy), postulates (the articles of faith), and theses (theological conclusions). Despite his sporadic attendance at theological lectures, Bacon seems to have had no comprehension of what the avant-garde theologians were doing. Perhaps this, more than any insistence on scientific values or the need for experimentation, brought him into conflict with his educated confreres, who apparently considered him, for all his flashes of brilliance and his scientific lore, something of a crank.

See also Albert the Great; Aristotle; Avicenna; Ethics, History of; Grosseteste, Robert; Joachim of Fiore; Neoplatonism.


Fr. Rogeri Bacon Opera Quaedam Hactenus Inedita, edited by J. S. Brewer (London: Longman, Green, Longman and Roberts, 1859), contains Opus Tertium, Opus Minus, Compendium Studii Philosophiae, and Epistola de Secretis Operibus et de Nullitate Magiae. For supplements to Opus Tertium, see Pierre Duhem, Un Fragment inédit de l'Opus tertium de R. Bacon (Quaracchi: Ad Claras Aquas, 1909), and A. G. Little, Part of the Opus Tertium of Roger Bacon (Aberdeen: University Press, 1912). Also see J. H. Bridges, ed., Opus Majus, 3 vols. (Oxford: Clarendon Press, 18971900; reprinted Frankfurt am Main: Minerva, 1964), Vol. II of which contains Multiplicatio Specierum as an appendix. For the complete text of Part VII, which is incomplete in Bridges, see F. Delorme and E. Massa, Rogeri Baconis Moralis Philosophia (Zürich, 1953).

Other writings by Bacon may be found in F. A. Gasquet, "An Unpublished Fragment of a Work by Roger Bacon," in English Historical Review 12 (1897): 494517, a prefatory letter to the Opus Maius or Opus Minus or both; E. Nolan and S. A. Hirsch, The Greek Grammar of Roger Bacon and a Fragment of His Hebrew Grammar (Cambridge, U.K.: Cambridge University Press, 1902); and H. Rashdall, ed., Fratris Rogeri Bacon Compendium Studii Theologiae (Aberdeen: Typis Academicis, 1911). Most of Bacon's remaining works have been published by R. Steele (with individual volumes by F. M. Delorme, A. G. Little, and E. Withington) in Opera Hactenus Inedita Fratris Rogeri Baconis, 16 fascicles (Oxford: Clarendon Press, 19051940). The Compotus (Fasc. 6), ascribed to Bacon, is, however, the work of Giles of Lessines. See also S. H. Thomson, "An Unnoticed Treatise by Roger Bacon on Time and Motion," in Isis 27 (1937): 219224, and F. M. Delorme, "Le Prologue de R. Bacon à son traité De influentiis agentium," in Antonianum 18 (1943): 8190.

English translations of Bacon's work are R. B. Burke, The "Opus Majus" of Roger Bacon, 2 vols. (Philadelphia: University of Pennsylvania Press, 1928; reprinted, New York, 1962), and T. L. Davis, Roger Bacon's Letter concerning the Marvelous Power of Art and Nature and concerning the Nullity of Magic (Easton, PA: Chemical Publishing, 1923). For a bibliography of Bacon's works, see F. Alessio, "Un seculo di studi su Ruggero Bacone (18481957)," in Rivista critica di storia della filosofia 14 (1959): 81108.

A discussion of the life and works of Roger Bacon appears in the introduction and appendix of A. G. Little, Roger Bacon Essays, Contributed by Various Authors on the Occasion of the Commemoration of the Seventh Centenary of His Birth (Oxford: Clarendon Press, 1914). Also see S. C. Easton, Roger Bacon and His Search for a Universal Science (New York: Columbia University Press, 1952), which contains an extensive and annotated bibliography. For a discussion of Bacon's philosophy, see T. Crowley, Roger Bacon, the Problem of the Soul in His Philosophical Commentaries (Louvain and Dublin: Éditions de l'Institut supérieur de philosophie, 1950), a good account of hylomorphic theory; D. Sharp, Franciscan Philosophy at Oxford (Oxford: Oxford University Press, 1930); and E. Heck, Roger Bacon. Ein mittelalterlicher Versuch einer historischen und systematischen Religionswissenschaft (Bonn, 1957). For Bacon's contributions to science, see Lynn Thorndike, A History of Magic and Experimental Science (New York: Macmillan, 1929), Vol. II, pp. 616691, which minimizes Bacon's contributions (a reaction to earlier exaggerations); and A. C. Crombie, Robert Grosseteste and the Origins of Experimental Science 11001700 (Oxford: Clarendon Press, 1953), pp. 139162, a more balanced account.

Allan B. Wolter, O.F.M. (1967)