BACON, ROGER

(b. England, c. 1214 or 1220; d. Oxford, England, c. 1292), mathematics, astronomy, natural philosophy. For the original article on Bacon see DSB, vol. 1.

Bacon has long been recognized as a key intellectual figure in the Middle Ages, but interpretations of his role have varied. The previous DSB article on Roger Bacon by

A. C. Crombie and John North will remain a classic and should be consulted. It is particularly important for the account of Bacon’s mathematics and astronomy. Since 1970, however, there have been significant new editions and studies of Bacon’s works on grammar, logic, natural philosophy, astrology, experimental science, and moral philosophy. There has been a real advance in the production of good quality Latin texts with accurate matching geometric diagrams. And so, step by step, scholarship is on the way toward a more critical appreciation of all of the achievements of Bacon as a philosopher, scientist, and moral philosopher/theologian. The only major alteration to the chronology of Bacon is the realization that he returned from Paris to Oxford around 1280.

In 1859, William Whewell set the tone for modern accounts of “Roger Bacon and the Sciences” (Whewell, 1859). He viewed Bacon as an advocate of experiment ahead of his time. Robert Adamson in 1876 considered Bacon a philosopher of science. In the 1900s, Lynn Thorndike (1914, 1916) and Pierre Duhem (Bacon, 1909) asserted that the role of observation in Bacon’s science was minimal and added nothing to the science. A. C. Crombie in his Robert Grosseteste and the Origins of Modern Science (1953) argued that the qualitative aspects of modern science originated at Oxford in the early thirteenth century. This interpretation was not universally accepted.

The present entry brings the scholarship up to date and gives an overview of Bacon’s program of research especially in the light of new textual discoveries and new studies. Much of the recent scholarship has emphasized that Bacon must be seen in the context of his own times and the scientific concerns of those times. To avoid anachronism one should interpret Bacon as a medieval scientist and not as an early modern or modern scientist.

The most significant advances in Bacon scholarship since 1970 have been the following: the discovery of the missing section of Opus maius on signs (De signis). The study of this and related logical texts has led to a better understanding of Bacon’s philosophy of language and semiotics. One has also gained a better understanding of his applications of learning to theology, a more precise knowledge of his understanding of mathematics, the first reliable text of his major work on natural philosophy, De multiplicatione specierum (On the multiplication of species), the first reliable text of the Perspectiva, a better understanding of the sources of the scientia experimentalis, a better knowledge of his moral philosophy.

Life and Works. Bacon remarks in the Opus tertium that around 1267 to 1268 he had devoted forty years to study since he had first learned the alphabet and that no other scholar worked some much in the arts and sciences as he had done. Some scholars use this text to argue that Bacon was speaking about his elementary education and was born c. 1220. Others hold that he was born c. 1214.

With the exception of the logical works, the Aristotelian Quaestiones are found in manuscript, Amiens MS Bibl. Mun. 406. They include two sets of questions on the Physica and the questions on the Metaphysica of Aristotle, the questions on the Liber de causis, the pseudo-Aristotelian De vegetabilibus. A second version of the questions on the Physica has recently been found in Philadelphia MS Free Library, Lewis Europe, ff. 77ra-85rb. It led to new critical research.

The early logical works consist of the Summa gram-matica, Summa de sophismatibus et distinctionibus and the Summulae dialectics (=Summulae super totam logicam). These works show that Bacon was indebted to the teaching of logic at Oxford and Paris in the 1230s and 1240s, especially to Robert Kilwardby. They received much critical study in recent years and show that Bacon was a mature philosopher of logic who was representative of terminist and premodist grammar.

Scholars have long held that Bacon was a pioneer in introducing the study of Aristotle as interpreted by Aver-roës and Avicenna to the University of Paris c. 1240. Recent research has shown that two Erfurt manuscripts

(Stadtbibliothek Q. 290 and Q. 312) once ascribed to Walter Burley (fourteenth century) belong to the first half of the thirteenth century. The editor of the questions on the Physica attributed these to Richard Rufus of Cornwall, a contemporary and opponent of Bacon. This research alters the accepted view of Bacon as the first to teach Aristotle at Paris (see Richard Rufus of Cornwall, 2003).

It has been demonstrated that already in the 1240s, Bacon confronted and reviewed some of the major issues concerning Latin Averroism that would become a vital part of philosophical discussion at Paris in the 1260s and 1270s. One can conclude that by 1248 Bacon ceased being a master of arts at Paris, became an independent scholar, and returned to England. He was back in Paris in 1251.

When Bacon joined the Franciscan order about 1256, he expected that it would support his scholarly work. Instead, he entered a ten-year period of enforced absence from teaching. He had been attracted to the order by the philosophical, theological and scientific example of Robert Grosseteste and Adam Marsh. He had personally known Adam Marsh and may have seen Robert Grosseteste.

Roger Bacon and Science. The Opus minus, minus, tertium, the related foundational work in philosophy of nature, De multiplictione specierum, and the work on burning mirrors, De speculum comburentibus, together with an optical lens, were sent to the pope c. 1267 to 1268. They were seen as a preamble to a major work on philosophy. Together with these in the 1260s, he produced the Communia naturalium, Communia mathematica, Epistola de secretis operibus naturae et the nullitate magiae. The Compendium studii philosophiae can be dated to about 1271. This is largely a work of polemic on the state of studies in Paris. The edition of the important work in medieval politics and statecraft in Latin translation from the Arabic, the Secretum secretorum, was completed at Oxford about 1280. The Compendium studii theologiae is usually dated to c. 1292.

One must bear in mind that Bacon in the 1260s is writing as an individual author for a patron, Pope Clement IV. Although a onetime master of arts, he was no longer a teaching master at the university. Still, much of his polemic is centered on the struggles in the arts and theology at Paris. The pope instructed Bacon in 1266 to ignore the rules of his order and to send him his remedies about a matter of some importance. What does this mean?

Bacon offered a structural critique of the scholastic practice in the universities. He favored language study and science over Sentence Method, and advocated training in mathematics and the sciences as requirements for students in theology. Bacon’s later works on languages and sciences were written in the specific historical and political context of the Mongol invasion of Europe, the sack of Baghdad in 1258, and the geopolitical situation of a Europe hemmed in by both the Mongols and Islam. His sense of world geography was aided by the travel reports of William of Roebruck. Bacon offered a criticism of the Latin Averroism/radical Aristotelianism of the schools.

The overall division of the Opus maius is Stoic: language study, natural philosophy/mathematics, and morals. The general context is theological: the arts and sciences leading to human well-being in this world and the next. Part One examines the causes of error in education and is critical of some theological limits on science. These causes are: belief in unworthy authority, long custom, uncritical popular opinion, and concealment of academic ignorance in a display of rhetorical wisdom. Part Two contains the pre-Cartesian view of truth and wisdom as a result of a universal revelation to the Hebrews that was transmitted through the Greeks, Romans, and Islam to medieval Christianity. Part Three deals with language study, grammar, semantics, and semiotics. Bacon’s semiotics is now seen as very important for medieval logic. His account of semiotics, De Signis, was discovered in 1978 (Fredborg, Nielsen, Pinborg, 1978). Bacon’s proposals were radical. He advocated language training in Hebrew and Greek. He wrote Hebrew and Greek grammars. Bacon’s ontology pointed toward the priority of the individual and the realist/nominalist issues in medieval thought.

Parts Four, Five, and Six of the Opus maius present the main themes of Bacon’s contribution to scientific education. In addition, one should add the scientific works mentioned above. It is important to see Bacon’s main contribution to science as one who advocated scientific education in an arts faculty that was dedicated to the linguistic arts. Bacon had a very wide reading knowledge of most of the newly translated work from Greek, Jewish, and Islamic philosophy and science. His major claim to fame in science is that he was the first Latin thinker to comprehend and write on most of the ancient sources of Optics. In brief, he initiated the tradition of Optics/Perspectiva in the Latin world. This tradition would be formulated as teaching text by both John Pecham and Witelo of Silesia, his contemporaries, and would be taken up by the tradition leading to both Johannes Kepler and René Descartes. In his Perspectiva(Opus maius, Part Five) and De scientia experimentali(Opus maius, Part Six), he outlined a sketch for a scientific method, one that takes Optics as the model for an experimental science. In fact, Bacon and his contemporaries succeeded in the endeavor to have Perspectiva added to the four traditional quadrivium university subjects: arithmetic, geometry, astronomy, and music.

Opus maius, Part Four, deals with mathematics and the applications of mathematics. Bacon presented reasons for a reduction of logic to mathematics and saw mathematics as the key to an understanding of nature. Clearly, he was proclaiming the usefulness of mathematics for knowledge. He was not doing mathematical theory. Following his abbreviation of the De multiplicatione specierum which shows how mathematics might be applied to physics, he dealt with the application of astronomy/astrology to human affairs, the uses of mathematics in religious rites as in chronology, music, symbolism, calendar reform, geographical knowledge, and a resume of astrology. It used to be thought that Bacon was a Platonist in his view of the absolute priority of mathematics. That view has been seriously qualified. He did not reduce physics to mathematics. His explicit work on mathematics, the Communia mathematica, was not an exercise in mathematics: it was a presentation of the common notions that are important for a variety of mathematical practices. Bacon himself acknowledged those who were better mathematicians, namely, John of London, Pierre de Maricourt, and Campanus of Novara (Molland in Bacon, 1997). In general, Bacon was more interested in what mathematics can provide about knowledge of the world as an aid to missionary activity. He sent a map of the world to the pope.

Bacon was very interested in the applications of astronomy/astrology to human events. Although committed to a doctrine of freedom of the will, he held to a deterministic notion of causation in nature based on the Islamic authority on astrology, Abu Ma’ Shar (Albumassar) and on the De radiis of al-Kindi. And because he held to a doctrine of universal radiation in nature, he had to account for the influence of the heavens on the human body and hence on the human mind. Much of the polemic in his later works consisted of a justification of this interest in the face of traditional theological objections. He was also interested in alchemy. It was his determined interest in both of these areas that led to disagreement with his superiors in the Franciscan order, specifically, Bonaventure.

The Philosophy of Nature. Bacon’s treatise De multiplicatione specierum written before 1267 is closely related to the study of light, vision and perception in the Perspectiva. David C. Lindberg (1983a) noted that Bacon took Grosseteste’s physics of light, a development of al-Kindi’s universal radiation of force, out of its metaphysical background. He developed a universal doctrine of physical causation.

The use of species in this account is not that of Porphyry’s logic or the perceptual notion of likeness. It is “the force or power by which any object acts on its surroundings” (Lindberg, 1983a, p. Lv). It denotes “al-Kindi’s universal force, radiating from everything in the world to produce effects” (Lindberg, 1983a, p. Lv). As Bacon himself noted, “species [force, power] is the first effect of an agent. ... the agent sends forth a species into the matter of the recipient, so that, through the species first produced, it can bring forth out of the potentiality of matter [of the recipient] the complete effect that it intends” (Lindberg, 1983a, pp. 6–7). This was a universal theory of natural causation as the background for Bacon’s philosophy of vision and perception. Most importantly, species is a uni-vocal product of the agent. The first immediate effect of any natural action is definite, specific, and uniform. This production is not the imparting of an external form. The species is educed from the active potency of the matter (Lindberg, 1983a, p. 13).

This was a first attempt in the Latin world to provide separate domains for material and spiritual being. Natural causation occurs naturally according to regular processes or laws of nature. There is no spiritual being in the medium as was commonly taught by other Scholastic philosophers. No, for Bacon, universal causation was corporeal and material, and matter itself in not just pure potentiality but was rather something positive in itself. Hence, the general philosophy of nature prepared the theoretical ground for the specific application of mathematics to matters of vision and perception.

Perspectiva. Bacon, in his Perspectiva and related works, presented his model for a careful and detailed application of mathematics to the study of nature and mind. In imitation of the De aspectibus of Alhacen (Ibn al-Haytham), he provided an application of geometry to vision that within the terms of reference of his times was partly successful.

Bacon’s approach to vision and perception, however, was not an exercise in contemporary mathematical optics.

It should be seen as the sketch of a philosophy of perception and mind. These topics constitute Part One and a section of Part Two. The text then opens onto a consideration of direct, reflected and refracted vision, and ends with the application of geometrical models for moral and religious considerations.

Part One and Part Two, distinction one and two deal with the structure of the eye, problems of vision and visual errors. The aim is psychological and epistemological, that is, to set out the conditions for certifiable or verifiable and certain perception. The theory of the eye is taken from the Galenic tradition handed on by Constantine the African’s translation of Hunyan ibn Isaq and from Avicenna and Ibn al-Haytham. For this tradition, vision occurs when the crystalline humor is altered by the intromission of visual species from the object. Vision is completed when the species proceeds through the vitreous humor to the optic nerve and through this to the common nerve. It is here that a common visual judgment is made. Bacon followed Ibn al-Haytham and imposed a geometrical model on the eye. Using this model, Bacon was able to give a geometrical account of radiation through the eye. How then does one avoid confusion in vision and gain verifiable clarity? For Bacon, the perpendicular ray was primary; the other rays were treated as cases of indirect vision. Yet, the rays were refracted in the rear surface of the crystalline humor.

Bacon was concerned with optical illusions, whether inverted images, magnification, vision of distant objects, the moon illusion, and such matters. He attempted to solve in a rational and experimental manner the puzzles found in Ptolemy, Ibn al-Haytham, and others. Still, he was a child of his sources. These do not provide him with the more advanced data and mathematical method that would be characteristic of the seventeenth century. Rather, Bacon provided a functional qualitative geometry of the eye and vision. He was committed to an intromission theory of vision but he combined it with an extramission theory of vision that avoided the anthropomorphisms of earlier theories. He used the extramission theory mainly to emphasize the active role of the eye in vision.

In Parts Two and Three, he was to a certain extent successful in applying geometry to problems of direct, reflected, and refracted vision. He moved the study of these matters to a new level. The geometrical arguments were worked out with careful diagrams and various appeals are made to experimental conditions. What are these conditions? Some of them are simple thought experiments or even reports of experiments (actual or imaginary) from earlier writers. It seems clear, however, that Bacon himself did experimental work with pinhole images, lenses, and discrete observations. This did not lead to a pure geometrization of nature and he inevitably fell back on physical, perceptual, and metaphysical arguments. One might argue that he lacked the notion of infinity that is present in modern geometry.

Bacon introduced another important item for science. He refers to the laws of reflection and refraction as leges communes nature. For Bacon in his account of nature in Communia naturalium and the later works in general, a general law of nature governed universal force. This universal law of nature is imposed on a world of Aristotelian natures. This notion would have a significant future in experimental science.

Bacon ended Part Three with an account of how a better understanding of the phenomena of nature could lead to a more accurate knowledge of natural phenomena mentioned in scripture. He found in visual phenomena significant metaphors and analogies for use in moral and religious teaching. Direct evidence of Bacon’s influence here in making science available for an educated public is seen in the use of his work by Pierre de Limoges in his influential work De oculo morali(On the moral eye), written in Paris between 1275 and 1289. MS Paris, BN Lat. 7434 owned by Pierre de Limoges contains an early copy of Bacon’s Perspectiva. All of this suggests Pierre de Limoges as a very early reader of Bacon’s works.

De scientia experimentali. Presupposing the Perspectiva, Bacon in De scientia experimentali and in related works on the halo and on burning mirrors situated this new scientific practice as a desired area of study in the medieval university. Starting from Aristotle’s account of empeiria(experience), Bacon argued that logical argument alone is not sufficient for the verification of things. Even arguments that have their origins in experience will need to be verified by means of an intuition of the things in the world. He distinguished natural scientific argument from moral and religious mystical intuition, although he did allow for the notion of a revealed intuition in science.

His aim was to provide a method for science, one that was analogous to the use of logic to test validity in arguments. This new practical method consisted of a combination of mathematics and detailed experiential descriptions of discrete phenomena in nature. It would be distinguished from the conjurations of magic and from religious belief. It would also be different from philosophy of nature and from broad optical knowledge. These two areas are important for broad theory, but according to Bacon, they do not provide access to minute, detailed experiments. Nevertheless, for his description of the first example of an experimental science, the study of the rainbow, Bacon was dependent on Aristotle, Seneca, and Avicenna.

His own important contribution is to be found in his calculation of the measured value of forty-two degrees for the maximum elevation of the rainbow. This was probably done with an astrolabe, and in this, Bacon advocated the skillful mathematical use of instruments for an experimental science. That Bacon had mathematical competence in this field can be seen in his account of the Halo(Duhem edition of Opus tertium) and in his complex arguments in De speculis comburentibus. Bacon took up Grosseteste’s theory of refraction and tried to work out the difficulties. Important here is his emphasis on the role of individual drops of water for the process of reflection and refraction. A correct account of the rainbow would appear some forty years after Bacon in the De iride of Theodoric of Freiberg.

A second task for experimental science was the discovery by experience alone of instruments (armillary sphere), new medical cures, chemical discovery, and military technologies. An important item here is the discovery of magnetism. It would seem that Bacon was reporting on the actual experimental work of Magister Petrus Peregrinus, author of De magnete, who is lauded in the Opus tertium as the only worthwhile experimentalist at Paris. Bacon has been lauded down the centuries for his medical learning, but recent scholarship limited the number of works attributed to Bacon. Still, it is important here to note that he did draw on medical practice to set out rules and procedures that, in a nonscholastic manner, would lead to a more experimental approach to nature. The third task was that of the prognostication of the future on the basis of astronomical or astrological knowledge.

The conclusion to the De scientia experimentali is important. Bacon presented the ideal of the philosophical chancellor who will organize science and its technological products for the benefit of the Res publica Christiana. In this, he was influenced by the important Mirror of Princes from the Islamic World, the Sirr-al-‘asrar (Secretum secretorum, Steele ed. [1909–1940, Vol. 5]). Stewart C. Easton proposed that this work was the guiding vision for Bacon’s reform of science. Steven Williams argued (1994) that Bacon completed the edition of this work after his return to Oxford c. 1280. Still, there is much cross-reference between this work and Bacon’s writings in the 1260s.

David C. Lindberg has given a succinct summary of Bacon’s model for an experimental science (Bacon, 1997). He saw four main aspects. First, Bacon’s theories of perspectiva were not his own creation. He took the best available materials from Greek and Islamic scholars and produced his own synthesis. Second, there is much evidence that Bacon himself did mathematical work and experiments with visual phenomena such as pinhole images and the measurement of the visual field. Third, as seen above, Bacon correctly calculated the maximum degree of elevation for the rainbow. Fourth, the experiments in Bacon, especially in the Perspectiva, served theoretically significant functions. It supplied observational data that required explanation in terms of a given optical theory. The usual role of experiment in Bacon is to “confirm, refute or challenge theoretical claims” (Bacon, 1997, p. 271).

One might have expected Bacon to have given equal treatment to astronomy, but in this field he was a child of his time. He reported on the accounts of Aristotle, Ptolemy, and Alfraganus (Steele ed., Vol. 4). He discussed the pros and cons in a scholastic manner but did not advance the field in the manner that he did for Perspectiva. Bacon’s Moralis philosophia (Opus maius, VII) concerns philosophy of religion, social philosophy, a theory of the virtues, an astrological sociology of religion and cultures, and an account of argument and rhetoric.

Roger Bacon had an immediate influence on early fourteenth-century philosophers such as John Duns Scotus and William of Ockham especially in terms of the role of the doctrine of species in epistemology, and in matters relating to semantics and semiotics (see Tachau, 1998). He would also seem to have been read by members of the Merton School. It was in the late Middle Ages that Roger Bacon came to be seen as a hero for English medicine. Reduced to a figure of comedy in the late sixteenth century, his manuscripts were recovered by John Dee and Sir Kenelm Digby. His scientific works were first published in the early seventeenth century as a result of the Rosicrucian interest in science. The Opus maius was first published in 1733. Roger Bacon’s works began to be studied with the new historical interest in medieval texts in the nineteenth and early twentieth centuries.

SUPPLEMENTARY BIBLIOGRAPHY

WORKS BY BACON

Opera quaedam hactenus inedita (=Opus tertium, Opus minus, Compendium studii philosophiae, Epistola de secretis operibus Artis et Naturae, et de nullitate Magiae). Edited by John S. Brewer. London, 1859. Reprint, Nendeln, Lichtenstein: Kraus Reprint, 1965.

The Greek Grammar of Roger Bacon and a Fragment of His Hebrew Grammar. Edited by Edmund Nolan and Samuel A.

Hirsch. Cambridge, U.K.: Cambridge University Press, 1902.

Un fragment inédit de l’Opus tertium de Roger Bacon. Edited by Pierre Duhem. Florence, Italy: Quarrachi, 1909.

Opera hactenus inedita Rogeri Baconi(Vols. 1–16). Edited by Robert Steele, Ferdinand M. Delorme, Andrew Little, et al. Oxford: Clarendon Press, 1909–1940.

Fr. Rogeri Bacon Compendium Studii Theologiae. Edited by Hastings Rashdall. Aberdeen, U.K.: Aberdeen University Press, 1911.

Roger Bacon Essays. Collected and edited by A. G. Little. Oxford: Clarendon Press, 1914. These essays, some on Bacon’s science, are still valuable.

“Les Summulae dialectics de Roger Bacon.”Archives d’Histoire Doctrinale et Litteraire du Moyen Age53. Edited by Alain de Libera (1986): 139–289; 54 (1987): 171–278.

Roger Bacon and the Sciences: Commemorative Essays. Edited by Jeremiah Hackett. New York: Brill, 1997. (Studien und Texte zur Geistesgeschichte des Mittelalters, Band LVII): Woodward & Howe on Geography/Cartography; Van Deusen on Music; Molland on Mathematics; Hackett on Astrology; Lindberg on Light, Vision and Universal Radiation of Force; Newman on Alchemy; Hackett on scientia experimentalis; Getz on Roger Bacon and Medicine; Williams on the Secretum secretorum.

Roger Bacon and Aristotelianism. Edited by Jeremiah Hackett. Vivarium 35 (September 1997): 129–320. This special edition of the journal is a study of the place of Bacon in the reception of Aristotle. See papers by Marmo, Trifogli, Donati, Wood, Noone, Long, Hackett.

OTHER SOURCES

Adamson, Robert. Roger Bacon: The Philosophy of Science in the Middle Ages. Manchester, U.K.: J.E. Cornish, 1876.

Bagliani, A. Paravicini. “Ruggero Bacone, autore del De ratardatione accidentium senectutis?” in Studi Medievali, 3rd ser., 28 (1987): 707–728.

Ebbesen, Sten. “The Dead Man Is Alive.” Synthese40 (January 1979): 43–70.

Fredborg, K. M., Lauge Nielsen, and Jan Pinborg, eds. “An Unedited Part of Roger Bacon’s Opus Maius: De signis.” Traditio 34 (1978): 75–136.

Hedwig, Klaus. “Roger Bacon’s Scientia experimentalis.” In Philosophen des Mittelalters, edited by Theo Kobush. Darmstadt, Germany: Primus, 2000.

Lindberg, David C. Theories of Vision from Al-Kindi to Kepler. Chicago: University of Chicago Press, 1978.

———, ed. De multiplicatione specierum and De speculis comburentibus. Oxford: Clarendon Press, 1983a.

———.Studies in the History of Medieval Optics, London: Variorum Reprints, 1983b.

———. Perspectiva. Oxford: Clarendon Press, 1996.

“Lines of Influence in Thirteenth Century Optics: Bacon, Witelo, and Pecham.” Speculum46 (January 1971): 66–83.

Maloney, Thomas S. “The Semiotics of Roger Bacon,” Medieval Studies 45 (1983): 120–154.

———. “The Extreme Realism of Roger Bacon.” Review of Metaphysics 38 (June 1985): 807–837.

———, ed. Compendium studii theologiae. Leiden, Netherlands: Brill, 1988.

Massa, Eugenio, ed. Rogeri Baconis Moralis Philosophia. Zürich: Thesaurus Mundi, 1953.

Matthews, Gareth B. “A Medieval Theory of Vision.” In Studies in Perception: Interrelations in the History of Philosophy and Science, edited by Peter K. Machamer and Robert G. Turnbull. Columbus: Ohio State University Press, 1978.

Molland, A. G. “Roger Bacon as Magician.” Traditio 50 (1974): 445–460.

———. “Roger Bacon and the Hermetic Tradition in Medieval Science.”Vivarium 31 (1983): 140–160.

———. “Roger Bacon’s Appropriation of Past Mathematics.” In Tradition, Transmission, Transformation: Proceedings of Two Conferences on Pre-Modern Science Held at the University of Oklahoma, edited by F. Jamil Ragep, Sally P. Ragep, and Steven Livesey. Leiden, Netherlands: Brill, 1996.

———. “Roger Bacon’s De laudibus mathematicae: A Preliminary Study.” In Texts and Contexts in Ancient and Medieval Science: Studies on the Occasion of John E. Murdoch’s Seventieth Birthday, edited by E. Sylla and M. McVaugh. Leiden, Netherlands: Brill, 1997.

Newman, William R. “The Alchemy of Roger Bacon and the Tres espistolae Attributed to Him,” in Comprendre et maitriser la nature au moyen age: mélanges d’hisgtoire offerts a Guy Beaujouan, Geneva: Droz, 1994.

Richard Rufus of Cornwall, In Physicam Aristotelis, edited by Rega Wood. Auctores Britannici medii aevi, 16. Oxford: Oxford University Press for The British Academy, 2003.

“Roger Bacon and the Reception of Aristotle in the Thirteenth Century: An Introduction to His Criticism of Averroes.” In Albertus Magnus and the Beginnings of the Medieval Reception of Aristotle in the Latin West, edited by Ludger Honnefelder, Rega Wood, Mechthild Dreyer, et al. Münster, Germany: Aschendorff Verlag, 2005.

Tachau, Katherine H. Vision and Certitude in the Age of Ockham: Optics, Epistemology and the Foundations of Semantics 1250–1350. Leiden, Netherlands: Brill, 1988.

Thorndike, Lynn. “Roger Bacon and Experimental Method in the Middle Ages.” Philosophical Review23 (1914): 271–298.

———. “The True Roger Bacon I,” and “The True Roger Bacon II.” The American Historical Review 21 (1916): 237–257, 468–480.

Whewell, William. History of the Inductive Sciences from the Earliest Times to the Present Times, Vol. 1. New York, 1859.

Williams, Steven J. “Roger Bacon and His Edition of the Pseudo-Aristotelian.” Secretum secretorum, Speculum69 (1994): 57–73.

Jeremiah, Hackett