Roger Bacon (1214/1220–1292), Master of Arts, contemporary ofRobert Kilwardby, Peter of Spain, and Albert the Great at theUniversity of Paris in the 1240s, was one of the early Masters whotaught Aristotle’s works on natural philosophy and metaphysics.Sometime after 1248–49, he became an independent scholar with aninterest in languages, mastering the known Greek and Arabic texts onthe science of optics. In 1256/57, either at Paris or Oxford, hejoined the Franciscan Order. By 1262 he believed that his universityreputation for advanced learning had suffered. And so, he sought thePatronage of Cardinal Guy le Gros de Foulque, Papal Ambassador toEngland (who later served as Pope Clement IV, 1265–68). On theinstruction of the Pope on June 22, 1266, Bacon quickly wrote“an introductory work,” theOpus maius, and therelated works,Opus minus andOpus tertium. He set outhis own new model for a reform of the system of philosophical,scientific, and theological studies, seeking to incorporate languagestudies and science studies, then unavailable, at the University ofParis.

In this project, he was partly successful. He wrote a new andprovocative text on semiotics, and influenced the addition ofperspectiva to mathematical studies (theQuadrivium) asa required university subject. He succeeded in setting out a model ofan experimental science on the basis of his study of optics. Thelatter was used in his extension of experimental science to includenew medicines and the general health care of the body. He did this ina new context: the application of linguistic and scientific knowledgefor a better understanding of Theology and in the service of theRes publica Christiana. Bonaventure and John Pecham were amonghis first readers. It is clear that with the possible exception of theuses or astrology and alchemy, Bacon shared in Bonaventure’sproject seeking a “reduction” of the sciences to theology.Bacon also found a sympathetic reader and interpreter in the greatsecular scholar of the Sorbonne, Peter of Limoges (d. 1306). He usesBacon’s optics for scientific and moral investigation. Baconthrough the work of Peter of Limoges may have influenced Raymond Lull.Sometime in the late 1270s or early 1280s, Bacon returned to Oxford,where he completed his edition with introduction and notes of theSecretum secretorum, a Latin translation of an Arabic text onthe education of the Prince, the Sirr-al-‘asrar. He believed itto be a work by Aristotle written for Alexander the Great. This workof advice to the Prince points to Bacon’s close connections tothe Papal Court through Pope Clement IV, the French Court throughAlphonse of Poitiers, and the English Court. His contacts with thePapal Curia were mediated by William Bonecor, Ambassador for KingHenry III. Bacon died at Oxford c. 1292.

• 1. Modern Research on Roger Bacon
• 2. Life and Works
• 3. Bacon’s early work on Grammar and Logic
  • 3.1Summa grammatica
  • 3.2Summa de sophismatibus et distinctionibus (SSD)
  • 3.3Sumulae dialectices (SD)
• 4. Bacon as an Aristotelian Commentator
  • 4.1 Roger Bacon and Richard Rufus:In physicam Aristotelis
  • 4.2 Bacon and Grosseteste: Knowledge, Science, and Intuition
  • 4.3 Bacon on Matter
  • 4.4 Bacon on Universals and Individuation
  • 4.5 Bacon’s Realism: On the Way to Late Medieval Nominalism?
  • 4.6 Bacon on Body, Soul and Mind: Early Works
  • 4.7 Bacon on Body, Soul, and Mind: Later Works
• 5. Bacon’s Later Philosophy: Language Study and Science in the Service of both Moral Philosophy and Theology
  • 5.1 Background
  • 5.2Opus maius/Parts One and Two
  • 5.3Opus maius/Part Three: On Language, theDe signis andCompendium Studii philosophiae
  • 5.4Opus maius/Parts Four, Five, and Six: Mathematics and Philosophy of Nature (De multiplicatione specierum,Perspectiva,Scientia Experimentalis)
  • 5.5Opus maius/Part Seven:Moralis philosophia
  • 5.6 Bacon’s political philosophy: theSecretum secretorum
• 6. Conclusion
• Bibliography
  • Primary Sources
  • Secondary Sources
• Academic Tools
• Other Internet Resources
• Related Entries

1. Modern Research on Roger Bacon

There are two modern approaches to Bacon. The first is the study ofthe physical, metaphysical, and related works of Bacon. Discovered in1848 by Victor Cousin in Amiens MS 406, these works were edited byRobert Steele and Ferdinand Delorme [OHI, 1905–1940]. With theexception, however, of some new work on the teaching on the soul,Bacon’s concept of matter, the doctrine ofexperientia/experimentum, and the doctrines of universals andindividuation, the doctrine of the heavens, and alchemy, the contentof these works has remained largely unstudied until the present time.Indeed, one can argue that “critical” scholarly study ofthese works has only just begun. In 2013, Silvia Donati made acritical study of Amiens MS 406. She has presented solid arguments forexcluding three of the eight philosophical commentaries from the canonof Bacon’s works. They are theQuestions on the PhysicsI-IV,Questions on Metaphysics XI, andQuestions onMetaphysics I-IV. These three texts were commonly used in allprevious scholarship. And so, great care must now be taken in readingthe traditional scholarship on early Bacon where these works haveoften been referenced.

The second and better known interpretation of Roger Bacon as ascientist is found in nineteenth and twentieth century writers on thehistory of science and has a solid basis in Bacon’s own work,e.g., the edition of theOpus tertium by J.S. Brewer [OQHI].Bacon’sPerspectiva (1267) [PRSP, 1996] presents a modelfor an experimental science that ushered in a new addition to thetraditionalQuadrivium (arithmetic, geometry, astronomy, music)in the new universities of the Latin West, namely, the study ofoptics. The university teaching text, “The Common Teaching onPerspectiva,” was written by Bacon’s Parisiancolleague,John Pecham. We have critical editions now for the majorscientific works of Bacon. SISMEL at Florence, Italy now houses aRoger Bacon research center. It has plans for future criticaleditions. A new international society for the study of Roger Bacon,The Roger Bacon Research Society has recently beenestablished.

In 1859, William Whewell set the tone for this modern account of“Roger Bacon and the Sciences” (Whewell 1858, p. 245). Heviewed Bacon as an advocate of experimentation ahead of his time. Inthe late nineteenth century, Robert Adamson and many othersinterpreted Bacon as a philosopher of science in the modern sense ofthe term. This understanding of Roger Bacon did not begin in thenineteenth century. Already in the late Renaissance, Francis Bacon hadcharacterized Roger Bacon as an exceptional figure among the schoolmen.^[1] Francis held that Roger Bacon had set aside the scholasticdisputations of his age and engaged in the mechanical understanding ofthe secrets of nature.

In the 1900s, Thorndike [LT1;LT2] and Duhem [LSDM, III, 442] assertedthat the role of observation in Bacon’s science was minimal andadded nothing to his idea of a science. This modern read-back ofmodern experimental method ignored the importance of optics inBacon’s model for a science (Lindberg, 1997). In recent studies(2006, 2012), Jeremiah Hackett has made explicit the manner in whichRoger Bacon served as a foil for Martin Heidegger’s discussionson the originality of modern science as a sign of Modernity. ForHeidegger, Bacon did not achieve the post-Galilean and Post-Cartesiandiscovery of a mathematical projection of nature and the consequentmodern experiment. He claimed that it was false to argue, as many haddone between 1880 and 1940, that Roger Bacon was the source for thepost-Cartesian concept of science. One can argue for the uniqueness ofmodern scientific method without setting aside the longue duree thatled to Kepler. One might note in passing that for Heidegger, Kepler isthe true forefather of modern science. In the post-World War II years,A.C. Crombie (1953) argued that the “qualitative” aspectsof modern science originated at Oxford in the early thirteenthcentury, specifically in the work of Grosseteste and Roger Bacon. Thisinterpretation received a critical response from AlexanderKoyré (1957) and others. Despite their significantly differentphilosophical committments, Heidegger and Koyré both sharedHusserl’s views on the distinctiveness of the modernmathematical projection of nature as a condition for controlledexperimentation. This was seen as a distinctive new phenomenon, amarker of modernity and something quite distinct from ancient andmedieval science. It was argued that Crombie read back some aspects ofmodern scientific method into the works of Grosseteste and Bacon.However, a recent study by Mattia Mantovani has signaled clearconnections between Bacon and Descartes’ approach to vision andperception (Mantovani 2020).

Thomas S. Kuhn (1976), however, maintained that Crombie did identify areal methodological connection between medieval and early modernscience. More recently, M. Schramm (1998) has argued that Bacon playsa significant role in framing the context for the beginnings ofmedieval, Renaissance and early modern notions of laws of nature. Thisdiscusion has now been taken up for research by Giora Hon and YaelRaizman-Kedar. The studies and editorial work of David C. Lindberg onBacon’s natural philosophy, for example, theDemultiplicatione specierum [DMS] andPerspectiva [PRSP](1983–1996) have emphasized the need to read Roger Bacon as amedieval scientist and not as an early modern or modern scientist.Thus, it is as a medieval philosopher, scientist, and theologian thathe must be properly understood. Despite the polarity generated by twoseparate modern traditions of interpretation, it should be noted thatthere is some continuity between the interests of Bacon theAristotelian commentator and Bacon the writer on science.

2. Life and Works

Bacon remarks in theOpus tertium [OQHI], written c. 1267 thathe had devoted forty years to study since he first learned thealphabetum and that no other scholar had worked as much in theArts and Sciences as he. Some scholars use this text to argue thatBacon was writing about his elementary education and therefore thatwas born c. 1220 [Crowley (1950), Easton (1952), Lindberg (DMS,1983)]; others hold that he was writing about his early universityeducation –Alphabetum philosophiae is a term Bacon usesin the chapter from which the following cited text is taken –and thus that he was born c. 1214 [Little (RBE, 1914), Maloney (CSTM,1988), Hackett (2016), Molland (2004)]. The text reads:

I have labored much in sciences and languages, and I have up to nowdevoted forty years [to them] after I first learned thealphabetum; and I was always studious. Apart from two of theseforty years I was always [engaged] in study [or at a place of study],and I had many expenses just as others commonly have... And it isknown that no one worked in so many sciences and languages as I did,nor so much as I did. Indeed, when I was living in the other state oflife [as an Arts Master], people marveled that I survived theabundance of my work. And still, I was just as involved in studiesafterwards, as I had been before. But I did not work all that much,since in the pursuit of Wisdom this was not required. ([OQHI], 65)

Some time after 1248, he set aside the common scholastic ways ofteaching in order to devote time to languages and experimentalconcerns. Thus, we can see the period from c. 1240–48 as thetime during which he lectured at Paris on Aristotle, on Grammar/Logic,and especially on the mathematical subjects of theQuadrivium.And so, depending on the chosen year of birth, the chronology would beas follows: (1) Bacon was born c. 1214, educated at Oxford c.1228–36, Master of Arts at Paris c. 1237–47/8, PrivateScholar 1248–56/7, active again at Oxford c. 1248–51, backin Paris 1251, Franciscan Friar at Paris c. 1256–57 to 1279,returning to Oxford c. 1280, died c. 1292. Or: (2) Bacon was born c.1220, educated at Oxford c. 1234–42; Master of Arts at Paris c.1242–47/8, active again at Oxford c. 1248–51, back inParis 1251, Franciscan Friar at Paris 1256/7 to 1279, returning toOxford c. 1280, died c. 1292. Further precision on the chronology mustawait the critical edition of all the works of Roger Bacon and carefulscientific study of these works in relation to other thirteenthcentury scholars.

The AristotelianQuaestiones are to be found in a singlemanuscript, Amiens MS Bibl. Mun. 406. The materials found in thismanuscript include two sets of questions on thePhysics and twosets of questions on theMetaphysics of Aristotle, thequestions on theLiber de causis, and the Pseudo-AristotelianDe vegetabilibus. As noted above, three of the questions on thePhysics and Metaphysics can now be excluded from Bacon’s canon.A new version of Bacon’s second set of questions on thePhysics inter-textually excerpted by another thirteenth-centuryauthor has recently been identified by Silvia Donati in PhiladelphiaMS Free Library, Lewis Europe, ff. 77ra-85rb (Donati 1997). This is animportant discovery that has enabled scholars for the first time tocarry out a critical-textual study of Bacon’s works onAristotle’sPhysics in the context of the development ofEnglish natural philosophy in the period 1240–1300.

The early logical works consist of theSumma grammatica,Summa de sophismatibus et distinctionibus and theSummulaedialectices [=Summulae super totam logicam]. These worksshow that Bacon is indebted to the teaching of logic at Oxford andParis in the 1230s and 1240s. They have received much critical studyin recent years. They reveal Bacon as a mature philosopher of logicwho is representative of terminist and pre-modist grammar and logic.Bacon’s writings on grammar and logic have a connection with theOxford ascribedLogica cum sit nostra and with the works ofWilliam of Sherwood. The logical works are clearly influenced by theteaching in Paris of Robert Kilwardby. They give evidence of Bacon asa philosopher who connects theLogica modernorum with newlogical and philosophical problems based on the natural philosophy andmetaphysics of Aristotle as commented on by Avicenna and Averroes.

Alain de Libera has argued that theSummulae dialectices istypical of mature works in the philosophy of logic c. 1250 and alittle later. If this is the case, can we exclude the possibility thatBacon continued teaching at some University up to ca. 1256/57? He doessay that he had a reputation as a scholar and teacher up to that time.Scholars have long held that Roger Bacon was a pioneer in theintroduction of the study of Aristotle as interpreted by Averroes andAvicenna to the University of Paris c. 1240. But to this we must addthe name of Solomon Ibn Gebirol (Avicebron). During the past ten yearsor so, research has shown that two Erfurt manuscripts (Amplon. Q. 290and Q. 312) ascribed to Walter Burley (1274/5–1344) by theAmplonius de Berka in the fifteenth century, actually belong to thefirst half of the thirteenth century. Rega Wood, the editor of thePhysics from the Erfurt MS Amplon. Q 290, has attributed thesequestions on thePhysics and most of the other works in thesetwo Erfurt manuscripts to Richard Rufus of Cornwall, a contemporaryand opponent of Roger Bacon [Wood 1997; Wood, IPA, 2003].

Recently, it has also been demonstrated that as Master of Arts atParis during the period of the First Averroism (c. 1240–48),Bacon had confronted and reviewed some of the major issues concerningthe Latin Averroism which eventually produced a major crisis at Parisin the period 1266–77 (Hackett 2005). And, as we will see below,Bacon, in his works from the 1260s, will revisit these topics.

Bacon joined the Franciscan Order about 1256/7; whether he did so atOxford or Paris is not known. At any rate, he was probably in Paris inthe late 1250s and was definitely there in the early 1260s. He hadbeen attracted to the Order by the philosophical, theological, andscientific example of Grosseteste, Adam Marsh, and other EnglishFranciscans. He had personally known Adam Marsh at Oxford c.1248–51. Because of their over-emphasis of a purportedcondemnation of Bacon c. 1278, scholars had tended to ignore or tonedown Bacon’s very real commitment to his Franciscan way of life.The past ten years have seen new work by Amanda Power (2013) andTimothy J. Johnson (2009, 2010, 2013) emphasize the compatibility ofBacon’s concerns c. 1266 with the mission of the FranciscanOrder as presented by Bonaventure and the Franciscan School at Paris.

In answer to the Papal Mandate received in July 1266, Bacon producedsome very significant works. TheOpus maius,Opus minus,and the related foundational work in natural philosophy,Demultiplicatione specierum, the work on burning mirrors,Despeculis comburentibus, together with an optical lens, were sentto the Pope c. 1267–68. They were seen as a preamble to aproposed major work on Philosophy. It remains a question as to whethertheOpus tertium was sent. Together with these works in the1260s, Bacon produced the Preface to the Works for the Pope,Communia naturalium,Communia mathematica,Epistolade secretis operibus naturae et de nullitate magiae.

Amanda Power (2013) has provided a masterful interpretation of the newcontext of Bacon’s post-1266 works for Pope Clement IV. Sheplaces Bacon in a Franciscan context within the wider mission ofChristendom in its relations with other cultures and religions. TheCompendium studii philosophiae can be dated to about 1271. Thislatter is a largely polemical work on the state of studies at Parisand an apology for his scholarly situation. It does, however, containan important section on his theory of language and translation. Hecompleted the edition of the important work on medieval politics andstatecraft, theSecretum secretorum, at Oxford some time after1280. It is clear that by 1266 and later, this important work played amajor role in Bacon’s understanding of the political uses of theexperimental sciences. He also produced an important work on thecalendar, theComputus. TheCompendium studii theologiaeis usually dated c. 1292, but its content does not differ from theconcerns of the work in 1266.

One must bear in mind that Roger Bacon in the 1260s is writing as anindividual author for a patron, Cardinal Guy le Gros de Foulque (PopeClement IV, 1265–68). A onetime Master of Arts, he was no longera teaching Master at the University of Paris. This gave Bacon thefreedom to address both philosophical (Aristotle) and theological(Augustine) issues in a manner denied to teachers in the Faculty ofArts, who were limited for the most part to disputations on the textsof Aristotle. He writes self-consciously as a representative of thetext-based practices of Robert Grosseteste and in opposition to thenew “sentence-methods” of the schools of theology. Hispolemical writings ca. 1267–68 are centered on the struggles inthe Arts and Theology at Paris. The Pope instructed Bacon in 1266 toignore the rules of his Order and to send him his remedies aboutmatters of some importance. It would appear from the context ofBacon’s works for the Pope that the remedies had to do witheducational matters at Paris, which at this time was the foremostuniversity of the Christian commonwealth. The remedies sought mustalso have concerned geo-political matters as well as the exigencies ofChristian missions.

The reception of the life and works of Roger Bacon is complex. Eachgeneration has, as it were, found its own Roger Bacon. Another studyby Amanda Power (2006) has provided a thoughtful account of thecomplex reception of Roger Bacon in England and of the extent to whichthe image of theDoctor Mirabilis is often colored by thechanging controversies of the present down through history.

3. Bacon’s early work on Grammar and Logic

Bacon has a complex notion of grammar. It ranges from the elementaryteaching of Latin through “rational grammar” (linguistics)to a knowledge of the sacred “Wisdom” languages. It isalso connected with a theory of signs and with thevisverborum, including the magical power of spoken language. Onenotices continuity between Bacon’s early works on grammar andlogic and his later works after 1260 on the theory of signs (Designis).

3.1Summa grammatica

In this work, Bacon draws directly from the commentary on Priscian(Priscianus minor) by Robert Kilwardby. This is representativeof early speculative grammar as it developed in Paris during the firsthalf of the thirteenth century. Bacon’s approach to grammar andlogic has a connection with the logic of that of William ofSherwood..

Part one of theSumma Grammatica sets out the rules governingboth common constructions with subject and verb and rules governingfigurative constructions. The latter include specific accounts of thefive figures of construction: antithesis, synthesis, prolepsis,syllepsis, and zeugma. This is borrowed from Kilwardby(Institutiones grammaticae, xvii, 153). In part two, Baconanalyzes the more difficult non-figurative constructions such asimpersonals, gerundives, ablative absolutes, interjections. In a thirdpart, he examines sophisms in terms of their subject-matter and rangesfrom a cursory treatment to more extended treatments typical of adisputed question. In the last section, there is a cursory analysis ofsome short sentences including adverbial constructions [lupus estin fabula] and some liturgical formulae [patris et filii etspiritus sancti, ita missa est]. The latter are problematic due totheir elliptical character. An account of Bacon’s intellectualrelationship to Robert Kilwardby can be found in Irène Rosier(1994).

As noted above, a major feature of this treatment of speculativegrammar is the fact that the reasoning is closely linked to thePhysics of Aristotle (Rosier 1994).^[2] This reasoned grammar is based on the belief that “art imitatesnature to the extent that it can” (Physics II, 219 4a21). Borrowing from Aristotle and Averroes and influenced by RobertKilwardby, Bacon exploits the distinction between the permanent andthe successive as the ground of the grammatical distinction betweenthe noun/pronoun and the verb/adverb. He applies this to thedefinition of grammatical category.

As Irène Rosier-Catach has noted, “The construction ofwords is conceived as a movement. The verb, the pivot of the sentence,signifies action and movement and needs for that reason two terms, aterminus a quo orprincipium and aterminus adquem orterminus (Summa Grammatica 66, 78). On onelevel, physical conceptualization is used to re-define certainnotions. Cases are properties allowing an expression to function as aterm of movement (Summa Grammatica 34); in this way, theaccusative expresses theterminus ad quem. At a second level,Bacon’s conceptualization allows him to state some very generalrules for the combination of categories” (Rosier-Catach 1997,70).

For example, Bacon argues that both the participle and the infinitiveby means of their verbal signification are not sufficiently stable tobe aterminus of motion. This is based on the premise that“nothing which is in motion can come to rest in something inmotion, no motion being able to complete itself in something inmotion.” And, using the principle that “the action is inthe patient as in a subject,” he tackles the issue ofgrammatical agreement. Further, the central principle for theorganization of terms is the notion of dependence(dependencia). Hence, the relation of natural dependencebetween the accident and the subject is reflected in the constructionof the adjective with its substantive.

Grammatical reasoning, then, finds itself wedged between physical andlogical reasoning. This can be seen in the analysis of the expression,est dies. Why one term and not two? What is the function ofdies? In an analysis of motion there are two terms. But inreason, one can see that the one term has two functions that arenecessarily present in every assertion. And whereas Logic requiresthat the subject be different from the predicate, Grammar as apositive science depends on the intellect and will.

The most significant aspect of Bacon’s grammatical analysis isone that will be replicated in his later work on semiotics. This ishisintentionalist analysis. The reasons connected togrammatical analysis cannot be discovered or applied mechanically:they are dependent on the signifying intention of the speaker(intentio proferentis). This kind of analysis is found inRobert Kilwardby and in many similar texts on sophisms. AsRosier-Catach puts it, “The correctness of a statement does notdepend solely on its conformity with therules of grammar butequally on its adequateness with its signifying intention. Sometimesindeed, because the speakerwishes to signify some preciseidea, he may legitimately distance himself from the normalrules” (Rosier-Catach 1997, 73). Still, this freedom is notabsolute; it must be justified linguistically. Even ellipticalexpressions such asita missa est have within them thecapacity to allow further application of formulas such ascantata,dicta, etc. Thus, to quote Rosier, “The rule-governednature of language-functions is to be found not only in the commonusage but also in those ‘authorized’ variations. It isprecisely this principle that Bacon will put to work at the semanticlevel when he conducts his analysis ofSigns [c. 1267].Beyond the ordinary usage of the sign, derivable from its institution,the speaker always has the liberty to use it in thetranslated way, the variation being in the majority of casesexplainable and for this reason comprehensible by the listener. Inother words, language is for man an instrument, a means. Thisvoluntarist/instrumental conception is to be seen likewise in thecontext of Bacon’s treatment of the magical power ofwords” (Rosier-Catach 1997, 73–74).

This imporant aspect of “the magical power of words” hasagain been examined carefully in terms of language study as it relatesto the uses of logic in theology by Rosier-Catach (2004). GraziellaFederici Vescovini (2011) has now presented a magisterial study of theclose connection of philosophy and natural magic in the Middle Ages,accentuating the notion of “the magical power of words” inrelation to Bacon and other medieval philosophers. This magical powerof words, derived from Alkindi, has a connection with Bacon’stheory of communication in part five of theMoralisphilosophia.

Bacon’s Logic (1240s):

• Summa de sophismatibus et distinctionibus (SSD)
• Summula super totam logicam (=Sumulaedialectices) (SD)

The late Jan Pinborg has described the terminist logic found in Baconand his contemporaries as “semantical analysis of a naturallanguage, viz. Latin, built on Aristotelian logic, especially theSophistici elenchi and thePeri hermeneias, and onthe development of grammar. This analysis stressed the truth value ofpropositions analyzed and its conditions, and therefore displayed whatcan be calleda contextual approach; that is, it was based onthe actual function and reference of the term in the proposition to beanalyzed. A given word could be used differently, or according todifferentsuppositions, and the rules for these differentuses helped to avoid ambiguities. The doctrine of supposition wasintended to solve both the relatively trivial ambiguities which arosefrom confusion of linguistic levels (man is white, man is a species,man is a noun) and ambiguities involved in quantification (ordistribution) theory. These problems were primarily solved in terms ofreference, since differentsuppositiones picked out differentranges of individuals.”(Jan Pinborg 1979)

One can see therefore why Bacon, through his concern with the centralrole of applied logic in guarding against ambiguity, saw the analysisof equivocation as central to the analysis of language. Against thegrowing Modist tendency to understand parts of grammar as indicativeof the objective constituents of things in the world, Bacon stressesthe importance of equivocation analysis. Since the imposition ofnames, the constant change in language use, and especially the ongoingimplicit shift of meaning in language are all important for a theoryof meaning, Bacon demands contextual language analysis. Here, onemight speak of Bacon’s “pragmatic” approach tolanguage theory.

3.2Summa de sophismatibus et distinctionibus (SSD)

Alain De Libera has provided a very precise summary of Bacon’splace in the history of logic and especially of the two early worksjust listed. He remarks:

TheSSD belongs to a literary genre found in Paris during thefirst half of the thirteenth century, theDistinctionessophismatum. It compares with theTractatus dedistinctionibus communibus in sophismatibus accidentibusattributed to Matthew of Orleans, theDistinctiones‘notandum’, theAbstractiones of HervaeusSophista, the tracts onDistinctiones sophismatum as well as‘anonymous’ treatises described by De Rijk and Braakhuis.Briefly, thedistinctiones have the task of listing the rulesto be used in the practice of sophisms and setting out the context,while thesyncategoremata set out the logical conditions forthe proper use of syncategorematic words. (De Libera 1997,105–106)

Generally, the SSD deals with problems of universal quantification, asfor example the uses of the wordomnis (’all’).Bacon pays close attention to words that present philosophicaldifficulties, such as ‘infinite’, ‘whole’, and‘negation’. The common logical topics are covered. Still,Bacon shows some originality in his treatment of‘inclusion’ or ‘scope’ in quantification. Healso develops the outline of what will become his own contribution inthe 1260s, i.e., his analysis of a “production of speech”.Bacon develops this analysis to deal with sentences such as‘Every animal is either rational or irrational’. Here, hiscontemporaries invoked a theory of natural sense to account for theprovision of semantic information on the basis of the order of thepresentation of the terms. But Bacon insists that one must take intoaccount (a) the signifying intention of the speaker, (b) thelinguistic expression, and (c) the sense that the listener provides.Bacon presents two basic positions: an expression must have parts thatenable the hearer to make an interpretation that will correspond withthe intention of the speaker. Thus, the actual expression alone isnecessary but not sufficient for an account of the meaning. Alinguistic analysis that involves speaker/hearer/expression is alsorequired.

The expression of the proposition alone is accidental and thuscontains only a relative sense. Further, the linear order of theexpression does not provide the listener with enough information aboutthe logical form. Knowledge of the logical form requires reference tothe mental proposition. This implies that every mental proposition,for both speaker and listener, is aninterpretation. Themeaning of any statement is a function of the understanding. Thispresentation of the speech act prepared the ground for Bacon’smature theory in his post-1260 works, theDe signis (DS),Compendium studii philosophiae (CSP), andCompendiumstudii theologiae (CST).

3.3Summulae dialectices (SD)

De Libera has placed this work at Oxford c. 1250, but notes thepresence of Parisian teachings in the text. The title given in theSeville MS,Summulae super totam logicam, provides a bettersense of the nature of the work. To summarize De Libera, this is themature work of a practiced teacher, not the work of a beginner. It isahead of other works of the 1240s in the skillful manner in which itexamines Aristotle and other newly translated works in philosophy andscience. The work is important for two new semantic positions: (1) thedoctrine of univocal appellation and (2) the doctrine of “emptyclasses” in predication. For Bacon, a word cannot be applied ina univocal manner to both an entity and a non-entity. This positionwill provide Bacon with a basis for his attack on Richard Rufus ofCornwall in his works after 1260, and especially in theCompendiumstudii theologiae (1292). This attack was not targeted at Rufusalone; it is written in opposition to the common teaching of the timeat Paris, according to which a word has a natural meaning and oncethat meaning is given, it remains a constant. For example, the term‘Caesar’ can cover both the once living Caesar and the nowdead Caesar. Bacon rejects this on the grounds that for him, terms areimposed on “present things” and there is nothing in commonbetween an entity and a non-entity or between the past, present, andfuture. Hence, Bacon is opposed to the notion of “habitualbeing”. Thus, terms have present appellation and their referenceto the past and future must be accidental. For Bacon, name andsignification are imposed on the present object, and these are openedto past and present on the basis of verbal tense. One might call it“supposition through itself for present things”. Anotherimportant aspect of SD is the complex theory of determination found inthe composition and division of the propositional sense.

The theory of imposition is fundamental to Bacon’s approach(Rosier & de Libéra 1986; Rosier 1994, 123–156).This allows for explicit and tacit changes of imposition of meaning incommunication and points to the need for linguistic analysis andcareful study of context in order to be strict about univocal meaning.Likewise, an interest in overcoming equivocation and ambiguity figuresthroughout Bacon’s logical works. Words can, indeed, be extended‘metaphorically’ to cover non-existing things. In thiswork of Bacon, one finds a combination of influences from both theOxford terminist logic and the Parisian pre-modist grammar of the1240s.

The reader can easily see that this treatment of “all oflogic” corresponds to a large extent to what is found in many‘modern’ logic books prior to the treatment of predicatelogic. It would be useful to show the extent to which Bacon’s SDprovides a template for later works on the totality of logic, such astheSumma Logica of William of Ockham and subsequent texts upto modern times.

4. Bacon as an Aristotelian Commentator

4.1 Roger Bacon and Richard Rufus:In physicam Aristotelis

Richard Rufus and Roger Bacon were two of the earliest Teachers ofAristotle’s natural philosophy and metaphysics at Paris, c.1235–50. The recent publication of Richard Rufus ofCornwall’sIn Physicam Aristotelis has made availablewhat is certainly a very important text for an understanding of theinfluence of Aristotle’sPhysics on the early traditionof English natural philosophy in the thirteenth century (IPA 2003).Richard Rouse has dated the text of thesePhysics questions“on the early side of the middle of the century” (Wood,IPA Introduction, 33). Silvia Donati and Cecilia Trifogli have mappedout the complex tradition of named and ‘anonymous’commentaries on Aristotle’sPhysics in 13th centuryEngland. (Del Punta, Donati & Trifogli 1996; Trifogli 1997, Donati1997; Trifogli 2000). As noted above, Rega Wood ascribes the text toRichard Rufus of Cornwall (died c. 1260). She claims that“Richard Rufus was the earliest Western teacher of the newAristotle whom we know.” He taught Aristotelian physics andmetaphysics as a Master of Arts at the University of Paris before1238. In the apparatus of the edition, Wood notes that these commentson Aristotle’sPhysics were later taken up by Roger Baconin hisQuestiones on Aristotle’sPhysics, and as aresult, she sees Roger Bacon as Richard Rufus’s successor as aParisian teacher of Aristotle’s natural philosophy. As evidencefor the influence of Rufus on Roger Bacon, Wood presents a discussionof three topics: (1) projectile motion, (2) the place of Heaven, and(3) the beginning of the world (IPA, 12–28).

4.2 Bacon and Grosseteste: Knowledge, Science and Intuition

Bacon holds that scientific knowledge is twofold: first, there is the“imperfect and confused knowledge” by which the mind isinclined to the love of the good and of truth. This implicit knowledgeis innate. Second, there is explicit rational knowledge. One part ofthis has to do with the knowledge of the principles of science; theother is the knowledge of conclusions. This latter is completeknowledge though it is not exhaustive. Bacon’s account of sense,memory, and experience is more extensive than that found inGrosseteste’sCommentary and reflects his own reading ofAvicenna, the medical tradition, and works on optics. Bacondistinguishesexperientia fromexperimentum. Experience(experientia) is the distinct knowledge of singular things, andall animals have this distinct knowledge of singulars. But not allanimals haveexperimentum, that is, a science of principlesbased on experience. As he puts it, “experience is the distinctreception of singulars under some aspect of universality, as is statedin the text [of Aristotle], but only the universal is grasped by theintellect.” Therefore, only humans and not other animals haveexperience [experimentum] ([OHI, XI] 16). Many animals have animage (imaginatio) of singular things and live by innate artand industry, naturally knowing how to adapt to changing weatherconditions. Human art, however, is acquired and is a science ofprinciples based on experience (experimentum principium).

One can express Bacon’s position as follows:experimentumis the universal source for our discovery of scientific principles.Scientific knowledge, once established, proceeds by demonstration.Experientia designates the simple perception of singulars. Onlyin a very loose sense can it be used of scientific knowledge.Sometimes, however, these two terms about experience are usedinterchangeably. In this account, Bacon has not yet come to his laternotion of ascientia experimentalis, and the experimentalverification (certificatio) of the conclusions of demonstrativeknowledge (ca. 1267). He is dealing only with experience as the sourceof the principles of our knowledge of art and science.]

In other words, at this stage, Bacon is mainly concerned withAristotle’s definition of experience in theMetaphysicsandPosterior Analytics, although one already notices that herelates the Aristotelian subject matter to the discussion inAlhacen’sPerspectiva. Nevertheless, it is also importantto note that these Aristotelian concerns withExperimentumare repeated in 1267 at the beginning ofOpus majus, Part Sixon exprimental science, and thus, Aristotle’sMetaphysics,Posterior Analytics andMeteorologytogether with theOptics of Ibn al-Haytham will form thenecessary philosophical background for Bacon’s laterc. 1266notions of the experimental sciences.

4.3 Bacon on Matter

In the later (post 1260)Communia naturalium, Bacon gives sixmeanings for the concept of matter. (1) Matter is the subject ofaction as when we say that wood is the matter for the action of thecarpenter. (2) In the proper sense of the term, matter is that which,with form, constitutes the composite, as in the case of every createdsubstance. (3) Matter is the subject of generation and corruption andhas the property of being an incomplete and imperfect thing in potencyto being a complete thing. (4) Matter is the subject of alterationsince it receives contrary accidents. (5) Matter can be considered asan individual in relation to the universal, the latter being foundedin its individual as in a material principle. (6) Matter is the namefor that which is gross, as when we say that earth has more matterthan fire (Sharp 1930, 127–151).

Form has a certain priority to matter as the end of generation and asthe perfection of the material principle. It is the principle ofaction and of knowledge. In general, for Bacon, matter is not a merepotency. It is an incomplete something (substance) and so for himmatter and form are two incomplete substances that integrate to makeoneindividual substance. In this one has a notion of matteras in some sense a positive thing. It is not a nullity. One way toplace Bacon’s position on matter is to situate it between thematerial monism of David of Dinant and the position of Aquinas thatmatter is a pure potentiality. For Bacon, matter as a being of essence(esse essentiae) has being in itself. For Aquinas, form alonegives being. But for Bacon the being of essence and existence belongtogether. Matter, therefore, can be a principle of division. Unlike amonist position, Bacon stresses the plurality of matters. The relationof universal and particular with respect to matter and form in Baconis complex. One notes the influence of Avicenna.

In both early and later works, Bacon objects to the idea that matteris one in number in all things. The background to this issue arises inthe 1240s to 1270s of theFons vitae of Avicebron (SolomonIbn Gebirol) and from Franciscan discussions at Paris on the nature ofthe unity of matter. Bacon holds that matter “is not numericallyone, but in itself and from itself it is numerically distinct innumerically different beings.” Still, he does not object to alogical unity of matter. For example, matter as potentiality is theoriginal source of the being of contingent things. This is thenon-being of the creature in contrast with the being of the Creator.Matter properly speaking is prime matter. This must be distinguishedfrom both natural matter and from artificial matterThus, Bacon willspeak of the matter of both corporeal and spiritual beings, and henceof “spiritual matter,” a concept that Aquinas found to becontradictory.

In his later works, and specifically in his works on naturalphilosophy, Bacon presents nature as an active agent. The form or thespecies is the first effect of any natural agent. The power of thespecies educes the emergence of the thing from the potency of matter.It does not simply produce a form/species and impose it on the matter.Matter has anactive potency, and this is actualized due tothe action of the natural external agent. See Michela Pereira,“Remarks on materia natualis”.

4.4 Bacon on Universals and Individuation

Bacon has two distinct treatments of universals and individuation: hisearly works (1240s) and later in theCommunia naturalium(1260s-70s).

In the works from the 1240s, Bacon distinguishes therealuniversal from themental universal. Hence, theuniversal as the ultimate basis of predication is not the species asmental intention. Universals in the primary sense as the basis ofscientific objectivity are extra-mental. Bacon’s presentation ofthis issue is complex. Certainly, he is not a complete Platonist inregard to universals. To the objection that since form is individuatedthrough its matter and whatever exists in things must exist in matteras individuated, but the universal is not such a thing, he repliesthat a universal is either in the mind or in things; if it is not inthe former, it has to be in the latter. A universal arises from commonmatter and common form and so has no need of being immediatelyindividuated: “And because the common matter and common formexist along with the proper matter and form of individuals, theuniversal is present in this way in singulars” ([OHI, X]242–243 = TTUM, 36). Hence, one cannot split apart the commonmatter from the particular matter or the common form from theparticular form of a particular individual.

In one question, Bacon rejects the view that universals areconstituted only by the mind. He holds that the universal in and ofitself is prior to the knowledge process: “This follows becausea universal is nothing other than a nature in which singulars of thesame (nature) agree; but particulars agree in this manner in a commonnature predicable of them, without any act of the mind” ([OHI,X], 242–243 = TTUM, 36). This sounds Platonic, but in fact forBacon there are no Platonic universals in a separate world; rather,real universals do exist, but they are found only in and withindividual things. There is a mutual interpenetration of common formand matter and proper form and matter such that there is just oneindividual, and so the common nature is realized in this or thatindividual. Bacon’s answer to the possibility of a universalbeing present in a singular is stated as follows:

Only three kinds of being are imaginable: either [being] in and ofitself, [being] in the mind, or [being] in things, but a universal isnot something that has being in and of itself and stands on its own,because then it would be a Platonic idea; neither [does it have being]in the mind, as we have seen… Again, a universal is a commonnature in which particulars agree; but Socrates and Plato and [others]of this sort cannot agree in a common nature which is in them unlessthe nature [be] in some way duplicated in them, because a universal isnothing other than a common nature extended into particulars andexisting in them as duplicated, in which all things truly exist. Andthus, without them [the particulars] there can be nouniversals…. ([OHI, VII, 243–244 = TTUM, 37)

For Bacon, there are two kinds of particular, the determinate here andnow particular and the indeterminate particular.

Bacon treats the problem of individuation both in the early Parisianlectures and the laterCommunia naturalium. This has givenrise to the issue of Bacon’s realism or his proto-nominalism.Itis addressed in the next section.

4.5 Bacon’s Realism: On the Way to Late Medieval Nominalism?

In the light of the foregoing, a key issue arises in his early works:even if Bacon disclaims being a Platonist with regard to universals,he is clearly a strong external realist. This realism is continued intheCommunia naturalium [OHI, 2–4] but with certainimportant qualifications. This polemical account of the discussion ofAristotle in the 1260s is understood by Bacon as an aid for the studyof theology. And now, it is clear that for Bacon, in the intention andexecution of nature,the individual has definite ontologicalpriority over genera and species. His account becomes an attackon contemporary positions influenced by Albertus Magnus that wouldsubordinate the individual to the universal. Species and genera arethere for the sake of the production of the individual. He states,“In no other field are the authorities in suchdisagreement.” Even Aristotle seems to contradict himself. Baconfinds a correct answer in theMetaphysics of Avicenna:

There are two kinds of nature, universal and particular, Avicennateaches in the sixth book of [his]Metaphysics.

Bacon adds,

Universal [nature] is the governing force of the universe [and is]diffused among the substances of the heavens [and] throughout all thebodies in the world; it is [that] in which all bodies agree andthrough which all are maintained at a certain general level ofperfection and well being. This universal nature is the corporealnature that is designated in the second genus, which is [that of]body, and this nature excludes all incompatible things which areabhorrent to the whole universe, such as a vacuum. ([OHI, II], 92 =TTUM, 85–86)

We see then that Bacon understands universal nature as supervening ona world of distinct individual natures such that corporeal action iscontiguous and that a vacuum is excluded. The “particularnature” is the directing power of the species with itsindividuals, and is divisible into the directive power of the speciesand of the individual. The example he gives is from embryology: thereis the directing power of the species intending the production of thehuman in general; it intends the production of the individualaccidentally. And there is the directing power of the individual,which aims at the determinate individual human as such and mankind ingeneral. As he puts it, “the universal is prior to theparticular in [both] the work and execution of nature, but isposterior in intent” ([OHI,II], 93 = TTUM, 87). He then statesthe ontological priority of the individual over universals asfollows:

But if we would speak about the universal nature that is the directingpower of the universe, [we should say that] it intends and bringsaboutan individual first and principally, about which thereis mention in theBook of the Six Principles. Nature operatesin a hidden manner in things: once a determinate man is generated, manas such is generated. And the cause of this is thatone individualexcels all universals in the world, for a universal is nothing but theagreement of many individuals. ([OHI,II], 94, = TTUM, 86)

He distinguishesthe absolute nature of an individual assomething absolute, that is, “that which constitutes it andenters its essence.” This absolute nature of an individual isontologically more important than that by which one individual hassome agreement with another. One can notice that Bacon is now writingas a person with a theological interest: “And because all thethings which I am treating are for the sake of theology, it is clearthrough theological reasons that a universal is not [favorably]compared to singulars. For God did not make this world for the sake ofuniversal man, but for singular persons…Therefore, speakingplainly and absolutely, we must say that an individual is prior innature [to a universal] both in operation and in intent,” and so“…it is necessary that the ranking according to prior andposterior be denominated absolutely and simply from the governingpower of an individual…” ([OHI,II], 94–95 = TTUM,88–89). Bacon knows that he is defending a position in rankopposition to the common view: “Since the whole rabble [atParis] holds the contrary position, because of certain authorities,the views of the latter must be presented” ([OHI,II], 96 =TTUM,90).

This account has given rise to opposing interpretations. TheodoreCrowley (1950) saw in these passages the beginnings of late medievalnominalism that would find its expression in William of Ockham. ThomasS. Maloney (1985) challenged this reading and argued that the laterRoger Bacon, like the earlier Bacon, was not a nominalist but anextreme realist. More recently, Chiara Chrisciani has argued thatalready in 1964, Camile Berube saw Bacon as the originator of theFranciscan doctrine of the direct intellectual perception of thesingular. He also noted the link between Bacon and William of Ockhameven though the path of influence was long and complex. She alsocorrectly noted that for Bacon, we have a sense-perception ofuniversals, one quite different from his contemporaries. Following K.Tachau and Y. Raizman-Kedar, Crisciani argues that the universals arematerially embodied in the intellect. In a recent study, whileagreeing with this position with respect to the material intellect, Iargued that it needed qualification. Perhaps we should hold that thereare elements of both ‘extreme-realism’ andproto-nominalism in this account in theCommunia naturalium. Inhis important essay on individuation in the fourteenth century, JorgeJ.E. Gracia (1991) argues for seeing this text and others as thebeginning of the strict tradition of late medieval nominalism.

4.6 Bacon on Body, Soul and Mind: Early Works

Bacon understands the soul to be a spiritual substance in union withthe Body. At this early stage, he does not hold the Avicennian notionof a separate agent intellect. In union with the body, the soul hastwo intellects, potential and agent. The former is directly connectedwith the sensitive powers and the object of this intellect is thesingular material thing. The agent intellect is directed upward andknows spiritual beings in its own essence. For Bacon, there is a kindof confused innate knowledge in the soul. This is not a Platonic idea.It is more like a disposition that inclines the soul towards knowledgeof the truth. Still, it is in some sense an innate knowledge of thefirst principles of knowledge. The agent intellect illuminates theimages and frees them from specific material conditions. Theuniversals are then impressed on the potential intellect.

4.7 Bacon on Body, Soul, Mind: Later Works

In hisCommunia naturalium, Bacon explains that he wrote hisaccount of sensation, the sensitive soul, and perception in thePerspectiva as a criticism of the common teaching of theAristotelian teachers in the schools. Further, he comes to theconclusion in theOpus maius that the greater philosophers inthe Greek, Islamic, and Christian traditions maintained that the AgentIntellectis God, the source and agent of illumination. Henow makes this position his own, and attacks those teachers who holdthat the agent and the potential intellects are parts of the soul.

Bacon’s short treatise on the soul inCN is titledDistinctio tertia de anima. It provides an interesting windowon contemporary debates c. 1267–70 at Paris. It belongs withAquinas’s masterful polemic,De unitate intellectus contraaverroistas and Siger of Brabant on Aristotle’sDeanima.

He divides the work into seven chapters: (1) On the production of theparts of the soul; (2) On the Sensitive Soul; (3) On the Unity andPlurality of the Intellectual Soul; (4) On the Composition of theRational Soul; (5) On the Powers of the Soul: whether they are partsof the soul; (6) On the Vegetative Soul; and (7) On the Parts of theIntellectual Soul.

The first chapter reviews the common teaching since 1250. Having notedthat before 1250, all philosophers and theologians held that thevegetative and sensitive souls came to be by way of natural generationand that the intellectual soul came from the outside, Bacon says,“And still to this day (c. 1269–70) the Englishtheologians and all true lovers of wisdom (philosophantes)uphold this position” ([OHI, IV], 282), that is, that theintellectual soul alone is created by God while the vegetative andsensitive souls in the human are produced from the potency of matterin accordance with the laws of nature. He argues that those opposed tothis position rely on the Pseudo-Augustine,De spiritu etanima, and on theDe ecclesiasticis dogmatibus byGennadius. Those who follow these sources, he states, hold that“the vegetative and sensitive souls are co-created with theintellectual soul…” He describes this as a kind of‘folk-psychology’. For Bacon and “allphilosophers,” embryology shows that the embryo is nourished andgrows prior to the infusion of the intellectual soul. Bacon states theproblem as follows:

But if the vegetative and sensitive souls were co-created with theintellective soul, asmany moderns teach publicly, then, theywould not precede the intellective soul in being. And so these peopleare forced to claim that one needs a double vegetative and sensitivesoul, one that is produced from the potency of matter through thepower of nature; the other is created with the intellectivesoul…But no authorities hold this position, and experts inphilosophy, therefore, dismiss it as nonsense. ([OHI, IV], 283)

Henry of Ghent among others advocated this doctrine of the co-creationof souls.

In the second chapter, Bacon attacks some of the leading philosophersat Paris: “But the leaders of the common philosophers at Parisfall into other deadly errors, which the theologians contradict”([OHI, IV], 284). For about ten years, the leader of the philosophers,“an erroneous and famous man,” held that “prior tothe existence of the rational soul, one must presuppose a specificsubstantial difference educed from the potency of matter which placesman in the species of animal, such that the intellective soul does notdo so…This is contrary to the philosophy of Aristotle and toall authors” ([OHI, IV], 284–85). A study of theQuestiones onDe anima indicates the earlier Parisiantradition out of which Bacon is working (Bernardini 2009; see alsoBernardini 2014). In the third chapter, Bacon makes explicit theobject of his polemic. It is the view commonly ascribed to Siger ofBrabant and the so-called Radical Aristotelians (Latin Averroists).Bacon states:

We are concerned with this second proposition on the unity andplurality of the intellective soul. Therefore, they [the LatinAverroists] argue that the intellective soul (animaintellectiva) is one in number among all human beings. Therefore,they cover their error when they are compelled [to respond] statingthat ‘through philosophy it is not possible to hold anythingelse, nor is it possible to have any other position throughreasonalone, but only through faith alone.’ ([OHI, IV],286–87)

This is the proposition that is analyzed and critiqued by ThomasAquinas in hisDe unitate intellectus contra Averroistas(1269) [TUIA]. It is also closely related to the celebrated doctrineof double truth imputed to the Latin Averroists by their Franciscanopponents. Bacon’s arguments, like those of Aquinas, dealspecifically with philosophical reasons for the mistaken positions ofthe Averroists. The first two arguments are moral arguments: if therewere one identical intellect in all humans, the same person would beboth virtuous and vicious. The denial that ‘this individualhuman thinks’ is contrary to both philosophy and faith. This iscontrary to theNicomachean Ethics and would lead to adestruction of moral philosophy.

The remaining arguments hold that the doctrine destroys “thelaws of nature,” that is, of natural philosophy and psychology.First, he presents Aristotle’s arguments against thetransmigration of souls. Second, he argues that this intellect wouldbe infinitized and in power equal to God. Third, he addresses theimportant issue of the connection between diverse imaginations and theintellective soul. This could lead to the same person being learnedand ignorant at the same time in respect of the same things. Again,injury to the sensory organs can lead to a person becoming insane. Ifthe sensory organs work, the existence of diverse imaginations willnot differentiate the intellect in different persons. Fourth, therewill be no unified object of knowledge. Bacon distinguishes betweenthe single object of the intellect and the “intelligiblespecies” by means of which we know that object:

For when it will be argued that thespecies will bemultiplied in diverse persons, I concede that the diverserepresentations of the same thing can be present to diverse personsbecause the thing itself produces itsspecies according toevery diameter, as was proved inDe multiplicationespecierum. And so, just as in the diverse parts of the air thespecies of the same thing are diverse, and come to the eyes ofdifferent perceivers, so it is the case with the intellects ofdifferent persons. ([OHI, IV], 289)

Thus, he makes a basic distinction between the thing which is theobject of knowledge and the representations (intelligible species) bywhich one knows them. Fifth, Bacon holds that the Averroists leave noroom for new knowledge. Sixth, against the Averroist position that alllogicians and grammarians must have the one same knowledge, Baconholds that one must distinguish between the cognitive habit by whichthe soul knows anything knowable and the object of knowledge in thesense of “the object of knowledge,” which is a unity.Seventh, based on Aristotle’s teaching on thepassionesanimae (species/concepts), he holds that just as the soul ismultiplied, so too will knowledge be multiplied. And so in a realsense, there is distinct and different knowledge in different humanbeings.

Chapters four to seven on the parts of the soul place Bacon in thecontext of the Franciscan and Dominican arguments on the parts of thesoul. These chapters show that Bacon was very active in the earlydebates at Paris in which the unity of substantial form in Aquinas wasstrongly criticized by the Franciscan School. Bacon is so critical ofAquinas’s position that he deems it heretical. He defends thenotion of plurality of forms while strongly arguing for the essentialsubstantial unity of the human being. Bacon also uses his remarks tolet the reader know that his study ofPerspectiva wasundertaken to criticize the common teaching on natural philosophy(including psychology) and medicine at the University of Paris.

This short treatise has the advantage of contextualizing Bacon’sworks in the 1260s in terms of the debates on Latin Averroism. Itwould appear that Bacon, like Bonaventure and Pecham, was an explicitopponent of the young teachers of the Arts at Paris, especially Sigerof Brabant. Bacon and Pecham shared the same scientific concerns(Hackett 2013a). And it would appear that Bacon’s treatises suchas thePerspectiva were written with this context in mind.Since, as we have noted above, Bacon provided a philosophical critiqueof the issues concerning Latin Averroism already as a teacher at Parisin the 1240s, we should see his intervention in the debates of1266–72 as the criticism of an emeritus Professor of Philosophy,now engaged with the theological arguments of the schools atParis.

5. Bacon’s Later Philosophy: Language Study and Science in the Service of Both Moral Philosophy and Theology

5.1 Background

At the beginning of theOpus maius and related works, Baconoffers a structural critique of scholastic practice in theuniversities. He favors both language study and science over the“Sentence-Method” as a way of interpreting the texts ofPhilosophy and of Scripture. And he advocates training in mathematicsand the sciences as requirements for students in theology. Second,Bacon’s later works on language and science are written in thespecific historical and political context of the Mongol invasion ofEurope, the sack of Baghdad in 1258 by the Mongols, and thegeo-political situation of a Europe hemmed in by both the Mongols andIslam. His sense of world geography was aided by the travel reports ofWilliam of Rubruck [Southern, WVI]. The wider historical context forBacon’s concerns has recently been outlined by Amanda Power(Power 2013). The overall division of theOpus maius isPlatonic/Stoic: language study, natural philosophy/mathematics,morals. The general context is theological and Franciscan: the artsand sciences leading to human well being in this world and the next.It is also clear that Bacon is constructing a “new model”for medieval philosophy, one in which Aristotelian concerns are takenup and transcended in a Neo-Platonism with significant Roman Stoicinfluence and adapted to moral philosophy and Christian theology.Metaphysics is taken up and completed in Moral Philosophy. The latterbecomes the end of linguistic and scientific study. Logic is reducedto mathematics, and the applications of mathematics become central toan understanding of the sciences (Perler 2005). The applications ofmathematics can in turn be used in religion and theology. Therefore,in his later works, especially in thePerspectiva andScientia experimentalis, Bacon will defineexperientia-experimentum in a distinctly new manner, one thattakes up and also goes beyond the use of this term in Aristotle. Hisnew definition advances on his ownQuestiones from the 1240s.Peter King has recently claimed that Ockham was the first to createthis new definition ofexperientia-experimentum (2003). He iscorrect that this definition is found in Ockham, but not in claimingthat this concept began with Ockham. The concept is formulated in thescientific works of Roger Bacon and is found in a number of Franciscanwriters including John Pecham well before the age of Ockham (Hackett2009).

5.2Opus maius/Parts One and Two

Before presenting the seven parts of theOpus maius, it isimportant to note a factor that is absent from the scholarship, thatis, how Bacon’s Islamic sources structure this major work. Thesesources, of course, are integrated with his Greek and Latin sources.Most important here for the architecture of the latter work is theDe scientiis of Alfarabi. The division of the sciences andthe reduction of the linguistic and natural sciences to moralphilosophy is strongly influenced by this text. Part four and thelatter section of Part six on prognostication, and Part seven, IV, isinfluenced by Abu Ma’shar’s Introduction to Astronomy andby his Book of Conjunctions. Part five on Perspectiva is a masterpieceof synthesis of most of the major Greek and Muslim texts on Optics.Especially important are the texts of Ptolemy, Alkindi, and Ibnal-Haytham. This synthesis clearly influences Bacon’s newunderstanding of an experimental science. And yet in addition to this,one must note that Ptolemy in hisAlmagest, Optics andAstrology influences Bacon’s understanding of method in thesciences as it impacts the integration of reason and experience. Andin the third part of the Scientia experimentalis,Bacon is influencedon the important commentary on Ptolemy’Astrology, namely, theCentiloquium by Abu Ja’far IbnYusuf Ibn Ibrahim. Butsince Bacon’sDe multiplication specierum isacknowledged by him as the key to his Optics, one must note thestructural presence of theDe Radiis attributed to Al-Kindi.This work provides the basis for his doctrine of species that will bespelled out for the geometry of vision in the Perspectiva. Since theOpus maius and related later works are intended as sketch fora grand linguistic, scientific, philosophical and theological work,one must note the important openness that Bacon has for the science,philosophy and theology received from the Muslim and Jewish worlds.This is very different from the Anti-Arabism and the intermittentAnti-Judaism that would become a central part of Western Renaissanceculture after 1300.

Part one examines “the causes of error” in education andis critical of some theological limits on science. These causes are:belief in unworthy authority; long custom; uncritical popular opinion;concealment of academic ignorance in a display of rhetorical wisdom.The polemic is presented as one of conflict among the canon lawyersand theologians at Paris concerning the reception of Aristotle andrecent works on Greek and Arabic sciences, especiallyastronomy/astrology. This is Roger Bacon’s appeal to the Wisdomof the Ancients

Part two contains the pre-Cartesian view of truth and wisdom as aresult of a universal revelation to the Hebrews that was transmittedthrough the Greeks, Romans, and Islam to medieval Christianity. Thisview would be influential in Philosophy up to the age of Francis Baconand Descartes. Roger Bacon links it to a doctrine of illuminationtaken from Augustine, Avicenna, and the commentary on thePseudo-Ptolemy: Centiloquium. He contrasts the tradition ofthe great philosophers such as Plato and Aristotle with the mythicaltraditions from ancient times.

5.3Opus maius/Part Three: On Language,De signis andCompendium Studii philosophiae

Part three deals with language study, grammar, semantics, andsemiotics, and contains Bacon’s general theory of signs. The1978 discovery by the late Jan Pinborg and his colleagues ofDeSignis, a missing section of part three, led to intense study ofBacon’s semiotics and the philosophy of language in his laterworks. Bacon’s proposals are radical.

Bacon’s concerns with language in his later works transgress thedisciplinary boundaries of the medieval university. First, he demandsthat the universities study the Wisdom languages, i.e., Hebrew, Greek,Latin in one list, or Hebrew, Greek, Arabic, and Chaldean in another.He wrote Greek and Hebrew grammars (GGHG). Bacon takes Latin as amodel for a natural language, the “mother language” of theWest. For Bacon, this language is dependent on Greek and Hebrew. Hedistinguishes the “vulgar language” or “language ofthe laity” from the “language of learning” of theclergy. For him, vulgar language cannot be used in learning; it doesnot have an adequate technical vocabulary.

Bacon’s relative originality consists in the fact that he bringstogether the semantic and semiotic concerns of both Arts and Theologyor, as one might say, Aristotle and Augustine, into a creativesynthesis. From Augustine, he carries over significant elements ofStoic Logic. From these concerns, he develops his own novel theory ofthe sign. In theCommunia naturalium, Bacon notes that he hadto develop a new logic needed to deal with his new interests in thesciences. Indeed, Bacon uses the wordssignification and itscognates in a manner quite different from the traditionalposition.

The commonly used medieval definition of a sign was substitutional orrepresentational: “A sign is that which shows itself to thesenses and presents something else to the intellect.” Thisdefinition is similar to that of Augustine inDe dialectica(p. 86): “A sign is something which is itself sensed and whichindicates to the mind something beyond the sign itself.”^[3] In this case, the parts of our language are given by either God or the human so that the thoughts of the speaker can be communicated to the mind of the hearer. The expressions in language stand for thethoughts of the speaker and represent them to the hearer. InDesignis, Bacon provides the following definition: “For thesign is that which, offered tothe senses or to theintellect, represents itself to that intellect, since not everysign is offered to the senses as the common definition of signsupposes. However, on the testimony of Aristotle, another kind isoffered only to the intellect.” He states that thepassionesanime (concepts/species) are signs of things, and suchpassiones are habits of the soul and species(representations/intentions) of the thing existing for the soul, andtherefore, “they are offered only to the intellect so that theyrepresent external things to that intellect” ([DS], 82). Someinterpreters claim that Bacon’s definition of sign is close tothat of to that of Augustine inDe doctrina Christiana:“For a sign is something that apart from the impression it givesto the senses, also causes something else from itself to be present tothe mind.”^[4] Augustine gives the examples of animal tracks leading us to think ofthe animal, smoke leading us to think of fire, human expressionsleading to our understanding the mood of a person, and soldiersanswering the call of the trumpet in battle and then knowing where tomarch.

One can see that Bacon in a manner uncommon for his times relatesAugustine’s definition of sign to the inferential notion of signin the works of Aristotle. And so one can also see how Bacon,influenced by Kilwardby and Fischacre, unites the different concernsof the philosopher and the theologian.

Bacon continues and states: “The sign is in the predicament ofrelation.” This may sound innocent, but in Bacon’s accountit has the effect of transforming the traditional relation between asign and its meaning, either a thing or a concept. The theologianswere aware of a twofold relation: that of sign to thing signified andsign to the perceiver of the sign. For the majority of theologians,the first relation is an essential and permanent relation; the latteris accidental and non-permanent. Bacon reverses this. He remarks,

The sign is in the predicament of relation and is spoken ofessentially in reference to the one for whom it signifies. For itposits that thing in act when the sign itself is in act and in potencywhen the sign itself is in potency. But unless some were able toconceive by means of this sign, it would be void and vain. Indeed, itwould not be a sign, but would have remained a sign only according tothe substance of a sign. But it would not be a definition of the sign,just as the substance of the father remains when the son is dead, butthe relation of paternity is lost. ([DS], 81)

And so it is not sufficient that a sign have reference to what itsignifies (accusative) in order to be a sign; it is also required thatit have an interpreter (dative) for whom it signifies. In medievaltheology, the thing signified (accusative) has priority, and was trueeven if there were no interpreters. The notion of this two-wayrelation is found in Bonaventure, Rufus, and Fishacre among others,and the thing signified holds ontological priority over therelationship of sign to perceiver.

For Bacon, the communicative relation to a hearer is basic, and therelation to the thing signified is important but secondary in thewhole context of communication. The common theological teaching heldthat the relation of sign to thing signified is primary andfundamental. Once a name has been instituted, it does not change(Maloney 1983b). And so, the name ‘Caesar’ can be used ofboth the living and the dead Caesar. Against Rufus and Bonaventure,Bacon held that this introduced ambiguity into language. Even in thecase of ordinary signs such as that of a tavern, they remain a signonly potentially if there are no customers or staff.

Bacon’s own classification of signs introduces distinctions thatreflect an integration of Augustine and Aristotle:

1.

Natural Signs

1.1

Signifying by concomitance, inference, and consequence

1.1.1

Necessarily

1.1.2

Probability

1.2

Signifying by configuration and likeness

1.3

Cause and effect

2.

Intentional Signs purposefully generated

2.1

Signifying conventionally by means of a concept

2.1.1

Linguistic signs by way of imperfect deliberation:interjections

2.1.2

Linguistic signs by way of perfect [completed] deliberation:other parts of speech

2.1.3

Non-linguistic signs (language of gestures, monk-signs, sign-boards)

2.2

Signifying naturally,in the mode of affect

2.2.1

Products of the sensitive soul: animal sounds

2.2.2

Products of the rational soul:groans, exclamations, cries of pain^[5]

The distinction between 1 and 2 is taken from Augustine’sDedoctrina Christiana. Bacon himself claims that he worked out thetypology himself prior to finding it in Augustine’s great workon interpretation. Modern scholars, however, believe that he must insome way have borrowed it from Augustine (Maloney 1995). Thedistinction between 2.1 and 2.2 is taken from the Aristoteliantradition as handed down by Boethius. Type 1 signs occur naturally aspart of the agency of nature. Type 2 are signs only because they havebeen willfully created as such by deliberation; included here arelinguistic and non-linguistic signs. However, Type 2.2 are designated‘natural’ in a sense that is different from Type 1. Thesesounds and groans are products of nature and happen instinctively butin an “animate” action.

Interjections are a problem. They are parts of language, conventionalsigns, and so conceptual, yet they are emitted suddenly and often dueto pain. They are similar in a way to the groans of animals (Type2.2). This discussion is common to writers on grammar and logic fromthe 1240s, especially in the works of Richard Kilwardby and similarauthors.

The signs in 1.1 on natural consequence indicate that Bacon hasintegrated not only Aristotle and Augustine but also the work ofAverroes on theRhetoric of Aristotle. Thomas S. Maloney hasargued that Aristotle’sDe anima plays an important rolein Bacon’s distinction between signs by nature and signs byintention (Maloney 1983a). Bacon provides an analysis of ambiguity andequivocation in theDe signis andCompendium studiitheologiae (Maloney 1984).

5.2.1 Bacon and the Semiotic Triangle

In the traditional semiotic triangle inherited from Plato andAristotle, the sign is a symbol and symptom of thepassionesanimae (concepts/species) in the soul and the latter in turn havea relation of similitude to extra-mental things. And so the relationof sign to thing is indirect. Bacon gets rid of the mediation ofconcepts/species and has the sign refer directly to the object. Inthis way, Bacon substitutes an extensional relation for an intensionalrelation. Words candirectly refer to individual things, bethey single objects in the world, mental objects, or philosophicalconcepts. Primarily, then, words refer strictly to the present object.Reference to past or future objects will require the extension ofunivocal terms by means of analogy or metaphor. Simply because a signexists, it will not follow from that alone that the object of the signexists. As we saw above, without the interpreter of the sign, a signis a sign in name only or potentially. Bacon does not deny theexistence of the concept/species, but notes that a second impositionof meaning is required to name it. As Umberto Eco puts it,“Bacon definitely destroys the semiotic triangle that wasformulated since Plato, by which the relationship between words andreferents is mediated by the idea, or by the concept, or by thedefinition” (Eco 1989, 61). The relation of sign to concept isreduced to that of a symptom, which is no longer a symbol. Here onecan see the preparation of the ground for the semiotics of William ofOckham and late medieval nominalism.

5.4Opus maius/Parts Four, Five and Six: Mathematics and Philosophy of Nature (De multiplicatione specierum,Perspectiva,Scientia Experimentalis)

Parts four, five, and six of theOpus maius present the mainthemes of Bacon’s contribution to scientific education. It isimportant to see his main contribution to science as one who advocated“scientific education” in an Arts Faculty that waspredominantly dedicated to linguistic arts. Bacon had a very widereading knowledge of most of the newly translated work from Greek,Jewish, and Islamic Philosophy and Science. His major claim to fame inscience is that he is the first Latin Western thinker to comprehendand write on most of the ancient sources of optics. In brief, heinitiates the tradition of Optics/Perspectiva in the Latinworld. This tradition would be formulated as teaching text by hiscontemporaries Pecham and Witelo. Bacon’s optics was also readand commented on in 14th century Italy by, especially by LorenzoGhiberti. It was known to and used by Leonardo Da Vinci. And it waspart of the tradition of learning that led to Kepler and Descartes. InhisPerspectiva andDe scientia experimentali, Baconoutlines a sketch for a scientific method, one that takes optics asthe model for an experimental science. In fact, he succeeded in hisendeavor in thatPerspectiva was added to the fourtraditional university subjects of thequadrivium: arithmetic,geometry, astronomy, music.

Opus maius, Part four, deals with mathematics and theapplications of mathematics. Bacon presents reasons for a reduction oflogic to mathematics (a kind of reversal of modern logicism) and seesmathematics as the key to an understanding of nature (Perler 2005).Clearly, he is proclaiming the “usefulness” of mathematicsfor knowledge; he is not doing mathematical theory. And the branch ofmathematics that is important here is geometry. He applies it indetail in the optical works edited by Lindberg. Following hisabbreviation of theDe multiplicatione specierum in part fourof the Great Work, which shows how mathematics might be applied tophysics, he deals with the application of astronomy/astrology to humanaffairs, the uses of mathematics in religious rites as in chronology,music, symbolism, calendar reform, and geographical knowledge, and aresume of astrology (Rutkin, 2019). It used to be thought that Baconwas a Platonist in his view of the absolute priority of mathematics.More recently, that view has been seriously qualified. He does notreduce physics to mathematics. Indeed, his explicit work onmathematics, theCommunia mathematica, is not an exercise inmathematics, but a presentation of the “common notions”that are important for a variety of mathematical practices. Baconhimself acknowledges those who were better mathematicians, namely,John of London, Pierre de Maricourt, and Campanus of Novara (Molland1997). In general, Bacon is more interested in how mathematics cancontribute to 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/astrologyto human events. Federici Vescovini (2011) has now provided theessential context and linkage between medieval magic and philosophy,enabling scholars to grasp the dimensions of fate and freedom asunderstood by medieval philosophers and theologians. Althoughcommitted to freedom of the will, Bacon held to a deterministic notionof causation in nature based on theIntroductorium Maius inAstronomiam of the Islamic authority on Astrology, Abu Ma’Shar (Albumassar), on theDe radiis of al-Kindi, and on theCentiloquium by Pseudo-Ptolemy (Ahmed Ibn Yusuf). And sincehe held to a doctrine of universal radiation in nature, he had toaccount for the influence of the heavens on the human body and henceindirectly on the human mind. Much of the polemic in his later worksconsists of a justification of this interest in an astrologicallynecessitated universe in the face of traditional theologicalobjections. These works play a big role as background for his naturalphilosophy inDe multiplicatione specierum. He was alsointerested in alchemy. It was his determined interest in some of theseareas of study that led to disagreement with his superiors in theFranciscan Order, specifically, Bonaventure.

5.4.1 The Philosophy of Nature

Bacon’s treatiseDe multiplicatione specierum, hismajor later work on physics, written before 1267, is closely relatedto the study of light, vision, and perception in thePerspectiva. David C. Lindberg (DMP, Introduction) has notedthat Bacon takes Grosseteste’s physics of light, a developmentof Al-Kindi’s universal radiation of force, out of itsmetaphysical background and develops a universal doctrine of physicalcausation.

Lindberg had already traced the history of the emanation theory oflight from Plotinus to Bacon. Lindberg notes the influence ofal-Kindi’s work on the rays of the stars but does not citeddetailed evidence. What Bacon achieves is a comprehensive theory ofphysical force divorced from psychological, moral, and religiousinterpretation. As Lindberg puts it (DMP, Introduction), in this work,Bacon does not formally examine divine illumination of the intellect,universal hylomorphism, the plurality of forms (properly qualified),and the separability of soul. He restricts himself to presenting afull theory of the physics of light. Species is the first effect ofany natural agent. As Lindberg puts it (DMP, Introduction),“This is a complete physical and mathematical analysis of theradiation of force--and, thus, of natural causation.”

The use of ‘species’ in this account is not that ofPorphyry’s logic or the perceptual notion of likeness. Itis“the force or power by which any object acts on itssurroundings.” It denotes “al-Kindi’s universalforce, radiating from everything in the world to produceeffects.” As Bacon himself notes,

species [force, power] is the first effect of an agent…theagent sends forth a species into the matter of the recipient, so that,through the species first produced, it can bring forth out of thepotentiality of matter [of the recipient] the complete effect that itintends ([DMS], 6–7). This is a universal theory of naturalcausation as the background for his philosophy of vision andperception. Most importantly, species is aunivocal product of theagent. The first immediate effect of any natural action isdefinite, specific, and uniform. This production is not the impartingor imposition of an external form. The effect of the species is tobring forth the form out of theactive potency of the recipientmatter. (DMS, 6–7)

This also leads to an attempt to provide separate domains for materialand spiritual being. Bacon is adamant on this point: spiritual andmaterial being are entirely separate. Natural causation occurs“naturally,” according to regular processes or laws ofnature. There is no “spiritual being” in the materialmedium as was commonly taught by other scholastic philosophers. Thatis, Bacon objected to the use of the term ‘spiritual being inthe medium’. No, for Bacon, universal causation is corporeal andmaterial, and matter itself is not just pure potentiality but israther somethingpositive in itself. So, in terms ofexplaining ‘spiritual/intentional being’ in the medium,Bacon is of the view that the introduction of such terms muddy thewaters, especially if you are trying to come up with a comprehensivedoctrine of physical force. Hence, the general philosophy of natureprepares the theoretical ground for the specific application ofmathematics to matters of vision and perception. It also allows forand requires a metaphorical extension of these terms to moral andreligious domains.

Recent scholarship on Bacon’s philosophy of nature, especiallythat of Yael Raizman-Kedar (Raizman-Kedar, 2009; Raizman-Kedar,dissertation, University of Haifa, 2009) places great emphasis on theimportance of the concept ofspecies for Bacon’saccount of perception and mind. She is correct to note that Baconplaces a kind of natural activity in the mind via species. This leadsin her view to natural species having a direct role in intellectualactivity as such. One could speak of the direct presence of material,corporeal species in the intellect itself (see section 5.2 above forBacon’s complex discussion of the role of signs in animal andhuman knowing). Here, and also in thePerspectiva, we can seethe importance of the cogitative sense, as it takes on anadministrative role in animals analogous to reason in human beings.But in this life, for Bacon, human beings cannot know things in theworld without the presence of species in the mind. Species as theexpression of universal agency act naturally in nature and in the mindin a certain limited sense. Yet, Raizman-Kedar claims, “the verysamespecies issued by physical objects operate qua materialspecies within the intellect as well.” She also claims that theconcept of divine illumination plays a secondary role in theacquisition of knowledge, and that Bacon

regarded innate knowledge as dispositional and confused, thespecies, representing their agents in essence, definition,and operation, arrive in the intellect without undergoing a completeabstraction from matter and retaining the character of agents actingnaturally. In this way, Bacon sets the intellect as separate from thenatural worldnot in an essential way, but rather in degree(my italics), thus supplying a theoretical justification for theability to access and know nature. (Raizman-Kedar, 2009, 131; after2012 the author writes as Kedar)

Raizman-Kedar correctly stresses the central role of species(material/corporeal) in the acquisition of intellectual knowledge ofmaterial particular things in the world. Further, she carefullydistinguishes between the role of hearing and sight in the knowledgeprocess.

Hackett (2018c) raises questions about this conclusion. He points to asignificant problem with the translation of a central passage inPerspectiva in support of this position. Further, by placingBacon alongside his confrère, one can see that the doctrine ofdivine illumination plays a central role in both pure intellectualknowledge, moral knowledge and knowledge of the natural world. Yes,the material species are a necessary but not a sufficient element inthe acquisition of pure intellectual knowledge. Without theilluminative process within from above, pure intellectual vision isblocked. It is not at all clear that one can claim that Bacon is amaterial monist. Bacon’s separation of the account of physicalspecies in the DMP could lead one to think he has to be a materialmonist, even with regard to species in the medium, sense, and reason.And there is one sense in which this is true. But in the end, as hestates in both the DMP and the PRSP, matter and spirit are twoentirely separate kinds of substance. Hence, at a deep level, Bacon isa substance dualist (medieval version).

5.4.2 ThePerspectiva andDe speculum comburentibus (1266–67)

In hisPerspectiva and related works, Bacon presents hismodel for a careful and detailed application of mathematics to thestudy of nature and mind. In imitation of theDe aspectibusof Alhacen (Ibn al-Haytham), he provided an application of geometry tovision that within the terms of reference of his times was successful.But he is critical of both Alhacen and Ptolemy. He sees himself asanswering some of the optical problems not solved by eitherauthor.

Bacon’s approach to vision and perception, however, is not anexercise in modern mathematical optics. It should be seen as thesketch of a physics of light as the basis for a philosophy ofperception and mind. The account of visual perception in terms ofnatural philosophy, medicine, and philosophy of mind is found in Partsone and a section of Part two. The account ofPerspectivasets out a consideration of direct, reflected, and refracted rays, andat the end of Part three concludes with the application of geometricalmodels for moral and religious considerations. The analysis of naturalvision provides analogies and descriptions for an understanding ofdivine influence.

Part one and alsodistinctiones one and two of Part two dealwith the structure of the eye, problems of vision, and visual errors.The aim is psychological and epistemological, that is, Bacon sets outthe conditions for certifiable/verifiable and certain perception. Thetheory of the eye is taken from the Galenic tradition handed down inConstantine the African’s translation of Hunyan Ibn Isaq andfrom Avicenna and Alhacen. For this tradition, vision occurs when thecrystalline humor is altered by the intromission of visual speciesfrom the object. Vision is completed when the species proceeds throughthe vitreous humor to the optic nerve and through this to the commonnerve. It is here that a common visual judgment is made. Throughoutthe text, Bacon makes reference to the kind of visual knowledgepossessed by animals, especially in the context of a discussion of thecogitative sense. Bacon follows Ibn al-Haytham and imposes ageometrical model on the eye, enabling him to give a geometricalaccount of radiation through the eye. How then does one avoidconfusion in vision and gain verifiable clarity? For Bacon, theperpendicular ray is primary; the other rays are treated as cases ofindirect vision, refracted in the rear surface of the crystallinehumor.

Bacon is next concerned with optical illusions, inverted images,magnification, vision of distant objects, the moon illusion, and suchmatters. He seeks in a rational and experimental manner to solve thepuzzles found in Ptolemy, Alhacen, and others. Still, he is a child ofhis sources, which do not provide him with the more advanced data andmathematical method that arose only later, in the seventeenth century.But they do provide him with a functional qualitative geometry of theeye and vision based on the best Greek and Islamic science. Bacon iscommitted to an intromission theory of vision, though he combines itwith an extramissionist theory that avoids the anthropomorphisms ofearlier extramissionist theories. He uses the latter theory mainly toemphasize the active role of the eye in vision.

In Parts two and three, he is to some extent successful in applyinggeometry to problems of direct, reflected, and refracted vision. Hemoved the study of these matters to a new level. The geometricalarguments are worked out with careful diagrams and various appeals aremade to “experimental” conditions. What are theseconditions? Some of them are simple thought-experiments or evenreports of actual experiments from earlier writers. It seems clear,however, that Bacon himself did experimental work with pinhole images,lenses, and discrete observations. This does not lead to a puregeometrization of nature, however, and he inevitably falls back onphysical, perceptual, and metaphysical arguments. One might argue thathe lacks the notion of infinity that is present in moderngeometry.

Bacon introduces another important item for science. He refers to the“laws of reflection and refraction” asleges communesnature. In his account of nature inCommunia naturaliumand the later works in general, Bacon’s view is that a generallaw of nature governs universal force. This universal law of nature isimposed on a world of Aristotelian natures. This notion would have asignificant future in experimental science.

Bacon ends Part three with an account of how a better understanding ofnatural phenomena could lead to a more accurate knowledge of thenatural phenomena mentioned in Scripture. He finds in visual phenomenasignificant metaphors and analogies for use in moral and religiousteaching. A solution to David C. Lindberg’s queries aboutBacon’s attempt to combine elements of the intromissionist andextramissionist theories of vision is addressed here. At one level, itseems to be an akward combination of two conflicting theories ofvision. This combination can be understood when one notes that Baconis making use of the important issue of grace and free will issue asthe moral-religious background for his discussion of vision. In otherwords, genuine theological concerns influence the manner in whichBacon constructs his analysis of vision in thePerspectiva.Thus, the analyses of Ptolemy and Alhacen had to be synthesized withina definite theological framework.

Direct evidence of Bacon’s influence here in making scienceavailable for an educated public is seen in the use of his work byPierre de Limoges in his influential text,De oculo morali(On the Moral Eye), written at Paris between 1275 and 1289. MS Paris,BN Lat. 7434, owned by Pierre de Limoges, contains an early copy ofBacon’sPerspectiva. All of this suggests Pierre deLimoges,(magnus theologus et astronomus) as a very earlyreader of Bacon’s works (Newhauser 2001). Both are genuinelycommitted to theimprovement of the task of the preacher. Here, we seethe priority for Bacon of preaching over theology, or rather, thelatter is in service to the former (Johnson 2009).

5.4.3 On the Nature of Experimental Science:De scientia experimentali (1266–67)

Presupposing thePerspectiva, inDe scientiaexperimentali and in related works on the halo and on burningmirrors Bacon situates this new scientific practice as a desired areaof study in the medieval university. It is consequent on the study ofPerspectiva. Starting from Aristotle’s account ofempeiria (experience), Bacon argues that logical argumentalone, even when it originates from experience, is not sufficient forthe “verification of things”. Even arguments that havetheir origins in experience will need to be verified by means of anintuition of the things in the world. He distinguishes scientificargument from moral and religious mystical intuition, although he doesallow for the notion of a revealed intuition in science. It is thiselement that clearly separates Bacon’s practice from that ofmodern science. Just as in his concern with the certification oflanguage to gain individual reference, so too in science, Baconclearly wishes to have a way of certification for knowledge of theindividual.

His aim is to provide amethod for science, one that isanalogous to the use of logic to test validity in arguments. This newpractical method consists of a combination of mathematics and detailedexperiential descriptions of discrete phenomena in nature. It would bedistinguished from the conjurations of magic and from moral andreligious belief. It would also be different from philosophy of natureand from broad optical knowledge. These two areas are important forexperimental science, but they constitute general principles, so thatin themselves and without experiment, they do not provide access tominute, detailed experiments. Nevertheless, for his description of thefirst example of an experimental science, the study of the rainbow,Bacon depends on the accounts handed on by Aristotle, Seneca, andAvicenna. He is not uncritical of these accounts.

One source for Bacon’s methodology in an experimental sciencehas been overlooked by the scholarship. It is clear to all that Baconmade much use of and privileged Ptolemy’s Optics. What has beenmissed is that Bacon was also influenced by Ptolemy’smethodology in the introductory chapter to theAlmagest. Thecombination there of experience and geometrical reason is in somerespects different and more detailed than in Aristotle’sscientific methodology. And so even as Bacon uses Aristotle’stexts, he is employing the methodological assumptions of Ptolemy.

Further, Bacon’s very close connection of experience and reasonis influenced by his concerns with medical matters. (Roger Bacon,De erroribus medicorum). This text provides a widerdiscussion of Chapter one ofOpus maius, Part six.

The context for Bacon’s writing on topics from theMeteorology of Aristotle came from the presence in Paris ofthe new translation of this work from Greek into Latin. With therecent critical edition of theAristoteles Latinus version oftheMeteorology, it is clear that Bacon is deliberatelyoffering a criticism of William of Moerbeke’s translation. Baconcontends that the translations are not adequate and that thetranslator did not know the required sciences, especiallyPerspectiva, proposing instead a more accurate mathematicalanalysis of the phenomenon of the rainbow.

Bacon’s own important contribution is to be found in hiscalculation of the measured value of 42 degrees for the maximumelevation of the rainbow. This was probably done with an astrolabe,and in this, Bacon advocates the skillful mathematical use ofinstruments for an experimental science. That Bacon had mathematicalcompetence in this field can be seen in his account of the halo in theOpus tertiium (OQHI) and in his complex arguments inDespeculis comburentibus. Bacon takes up Grosseteste’s theoryof refraction and tries to work out the difficulties in the latter. Itwould appear at first glance that Bacon is rejecting the notion ofrefraction out of hand (Lindberg 1966), but in fact he is onlydemonstrating that refraction as formulated by Grosseteste did notmake experimental or rational sense. Bacon knew the rules governingthe geometry of refraction. Important here is his emphasis on the roleof individual drops of water for the process of reflection andrefraction. The new research on theDe iride of Grossetesteby Cecilia Panti and the other editors of the Oxford/Durham RobertGrosseteste project will shed much light on these matters. A correctaccount of the rainbow would be summarized some forty years afterBacon in theDe iride of Theodoric of Freiberg (d. c. 1307)[TFT], with his account of a single reflection and double refractionin single drops of water.

A second task for experimental science is the discovery by‘experience’ alone of instruments (e.g., the armillarysphere), new medical cures, chemical discovery, and militarytechnologies. An important item here is the discovery of magnetism. Itwould seem that Bacon is reporting on the actual experimental work ofMagister Petrus Peregrinus (fl. 1260–77), author ofDemagnete, who is lauded in theOpus tertium as the onlyworthwhile “experimentalist” at Paris (see Silvia Nagel2012). Bacon has been lauded down the centuries for his medicallearning, but recent scholarship has limited the number of worksattributed to Bacon. Still, it is important to note that he did drawon medical practice to set out rules and procedures. Here, the recentresearch of Agostino Paravicini-Bagliani (1991, 2000) shows that Baconshared these interests with other outstanding scholars such as Peterof Spain (Pope John XXI). The very concept of the ‘prolongationof life’ so forcefully proposed by Bacon in his later worksfound very receptive readers at the Papal Curia in Viterbo. The PapalCuria had by 1266 become a center for medical and scientific study.The third task is that of the prognostication of the future on thebasis of astronomical/astrological knowledge. This section, dependingon Pseudo-Ptolemy,Centiloquiium and Abu Ma’shar notesthat this revelatory divination is earier and more available than themore complex regular astronomy that requires constant observation andthe skillful uses of Tables and Instruments. These are not alwaysreadily available.

The conclusion to theDe scientia experimentali is important.Bacon presents the ideal of the “philosophicalchancellor”who will organize science and its technologicalproducts for the benefit ofRes publica Christiana. In this,he is influenced by the important “Mirror of Princes” fromthe Islamic World, theSirr-al-‘asrar (Secretumsecretorum) (OHI, V). Stewart C. Easton (1952) proposed that thiswork was the guiding vision for Bacon’s reform of science.Williams (1994) has argued that Bacon completed the edition of thiswork after his return to Oxford ca. 1280 or a few years before thatdate. Still, there is much cross reference between this work andBacon’s writings in Paris ca. 1266–71.

David C. Lindberg (1997) has given a succinct summary of Bacon’smodel for an experimental science [RBS]. He sees four main aspects.First, Bacon’s perspectival theories were not his own creation.He took the best available materials from Greek and Islamic scholarsand produced his own synthesis. Second, there is much evidence thatBacon himself did mathematical work and experiments with visualphenomena such as pinhole images and measurement of the visual field.Third, as seen above, Bacon correctly calculated the maximum degree ofelevation for the rainbow. Fourth, the experiments in Bacon,especially in thePerspectiva served “theoreticallysignificant functions” by supplying observational data thatrequired explanation in terms of a given optical theory. The usualrole of experiment in Bacon is to “confirm, refute, or challengetheoretical claims.”

One might have expected Bacon to have given equal treatment toastronomy, but in this field he was a child of his time. He reports onthe accounts of Aristotle, Ptolemy, and Alfraganus (OHI, IV). Hediscusses the pros and cons in scholastic, but does not advance thefield as he did forPerspectiva.

5.5Opus maius/Part Seven:Moralis philosophia

Bacon’sMoralis philosophia (=Opus maius, VII= RBMP) comprises the philosophy of religion, social philosophy, atheory of the virtues, an astrological-sociology of religion andcultures, and an account of argument and rhetoric.

Bacon describes the object of moral inquiry as follows: “Thisscience is preeminently active, that is, operative, and deals with ouractions in this life and the other life” ([RBMP], 3). It isfocused on human action. Of course, many human actions deal withissues that are the concern of the natural and linguistic sciences.Bacon notes that these sciences are active and operative but concerned“…with artificial and natural works which refer to thespeculative intellect, and they are not concerned with those thingswhich refer to the practical intellect, which is called practicalbecause it exercises operations of good and evil” ([RBMP],3). These works of the human being (operabilia) are“…more difficult to know than the objects of speculativeknowledge.” These include “…the highest truthsconcerning God and divine worship, eternal life, the laws of Justice,the glory of peace, and the sublimity of the virtues” ([RBMP],247). For Bacon, the human ability to deal with these topics isaffected by a certain corruption of the human will.

Moral science has two parts. The first is speculative, dealing withultimate moral truths. The second deals with the process of moralpersuasion: “The practical part is related to the first part asthe curing of the sick and the conserving of health, which are treatedin practical medicine, are related to that part of medicine whichteaches what health is…” ([RBMP], 248).

Part one deals with the object and method of morals science and withan outline of a philosophical anthropology based on Platonic,Aristotelian, and Stoic texts in which Bacon argues for an Augustinianview of the place of human beings in the world. This includes asection on metaphysical proof for God’s existence. And theancient source texts are treated as testifying to the universalreligion of Christianity. Part two is a very brief outline of thestructure of social life, taken from Avicenna.

Part three, the most substantial in the book, is concerned with virtueand vice. Bacon’s own text for this part of theOpusmaius still exists and one can see his personal editorial remarksin the margins. He did not have time to write a formal treatise, andso he presents an anthology of texts from Seneca and excerpts fromCicero with comment. This is preceded by a brief resume of Aristotleon the virtues. But it is clear that Bacon favors the image of theStoic wise person as his model for virtue. Bacon places great emphasison magnanimity as a virtue for the Prince and Prelate. Magnanimity ofthe greatest of the natural virtues. And it must not be confused withChristian humility. This distances Bacon from Bernard of Clairvaux andBonaventure. For Bacon, Christian humility has its own distinctiverole reflecting the relation of the human to the cosmos and to God.Above all, Bacon is concerned with reproducing as much of theAristotelian and Stoic accounts of virtues as possible, and he isconcerned with making theDialogues of Seneca known to PopeClement IV. In particular, he is most of all concerned withSeneca’sDe ira, which he regards as a fundamental textfor the moral instruction of princes and prelates. Certainly, Bacon,as he does in theSecretum secretorum, presents himself as amoral advisor to Princes.

Part four provides an astrological sociology of human nations or“sects”, relying on the moral/political account ofal-Farabi and on the astrological views of Abu Ma’shar(Albumassar). Bacon had a wide knowledge of the world including thecustoms of the Mongols, and so he compares Mongol, Jewish, Arab, andPagan civilizations.

Part five deals with the role of rhetoric in moral persuasion. Baconis convinced that rhetoric is closely connected with logic, andbelieved that the university system failed by teaching only grammarand logic (linguistics). The omission from the university curriculumof rhetoric and poetics, as found in Aristotle and as interpreted byal-Farabi and Averroes, was in Bacon’s view a mistake. He knowsthe latest translations and remarks:

But al-Farabi has presented to us the meaning of this kind ofargument, and Avicenna, al-Ghazali, and Averroes have done likewise.Because of this, one ought to present an account of the nature ofpoetic argument, and it falls tologic alone to compose sucha book, since the composition of argumentation pertains tologic alone…The appropriate presentation of thisargument is found in [my]Moralis philosophia, and in itsuse, and likewise in theological proofs and doctrines; and in suchmoral matters, this kind of argument moves a [person] much more thandoes a demonstrative argument since it has much greater power. And Ihave already composed a treatise on this [rhetorical-poetic] argumentin my works onlogic, and I have shown there what is properto this science. ([OHI, XVI], 16–17)

He continues and notes that according to Aristotle and al-Farabi, thisargument makes use of appropriate language so that the self can be ledto virtue and to overcome of vice. He then links up the Greek andIslamic sources with the regular sources in the Latin tradition suchas Cicero, Seneca, and Augustine. And he distinguishes carefullybetween demonstrative, dialectical, and rhetorical forms ofargument.

5.6 Bacon’s Political Philosophy: theSecretum secretorum

Bacon devoted considerable time to the study of this work, the Latintranslation of the Arabic work on statecraft in the tradition ofMirrors for Princes entitledSirr-al-‘asrar. He worked onthe text at Paris and completed the edition of this text withintroduction and notes at Oxford after his return there from Paris c.1280. This is the most important text on government and the educationof the Prince prior to the writing ofThe Prince byMachiavelli. The work is divided into four parts. Part one begins withthe letter of Alexander to Aristotle and deals with the king’smaintenance of the kingdom. It deals with virtues, largesse, andgifts. It is an account of the behavior expected of a King. Part twodeals with health care, medicine, and the origins of the sciences.Part three deals with alchemy and with the human emotional structure.Part four deals with physiognomy and anthropology. Bacon’sintroduction is substantial, consisting of seven chapters. It isclosely connected with his account of astrology inOpus maius,part four, and withscientia experimentalis in part six. Hissources are mostly Islamic and include theDe radiis andDeaspectibus of al-Kindi and the introduction to astrology of AbuMa’shar. Bacon proposes a kind of statistical predictiveastrology, and so has to deal explicitly with the issue of freedom anddeterminism. He objects to a kind of infallibilist necessitarianismand thinks that provided “possibility” and“contingency” can be guarded, one can predict what canhappen in nature and in human society (due to the effects of theelements on temperament) in a general manner. Thus, the ruler willhave need of the astrologer who will function as a kind of doctor,psychologist, sociologist, and political theorist. This is a far cryfrom a contemplative ethics. It is significant that in the workentitledErrores philosophorum ascribed to Giles of Rome, acontemporary of Bacon at Paris, many of Bacon’s sources areseverely criticized. In theDe regimine principium (1280s),Giles, unlike Bacon, provides a moral education for the prince that isentirely based on Greek and Latin sources, especially onAristotle.

The idea of secrecy and secret books associated with Roger Baconcontinued into the Renaissance (Kavey 2007), with the depiction ofRoger Bacon on stage in a drama by Robert Greene.

6. Conclusion

It will be clear from this account that Roger Bacon was an importantteacher of the Arts at Paris in the 1240s. He was ahead of his time inthe vigorous manner in which he integrated the new Aristotle with thetraditional Latin traditions of grammar and logic. He taught for along period in the Arts. He later called himself an expert in thephilosophy of Aristotle as interpreted by Avicenna and Averroes. Andwe should also add Avicebron (Solomon Ibn Gabirol). By 1248–49 heseems to have become an independent scholar. He then, it would seem,returned to England, where, under the influence of Adam Marsh, friendof Robert Grosseteste, Bishop of Lincoln, he was attracted tointerests associated with both scholars: language study including thelearning of ancient languages, experimental concerns such as opticsand experimental science, and a renewed critical study of the text ofScripture. When Bacon returned to Paris in the 1250s, he was to opposewhat had become a profound change in the methodology of universitylearning, that is, the introduction of the“Sentence-Method” into the study of theology. For Bacon,this was a destruction of practices that he associated with RobertGrosseteste. Taking up the flag of the Bishop of Lincoln (d. 1253), hebecame the great critic of the Parisian mode of doing philosophy andtheology. As we saw above, Bacon was already by 1266 very concernedwith the new heterodox interpretations of Aristotle found in theFaculty of Arts. His later works for Pope Clement IV must be read inthe context of the Parisian debates on Latin Averroism(1266–1277).

The later Roger Bacon has a good knowledge of the geography andhistory of the world and an awareness of geo-politics. In thiscontext, he devoted much time to the important work on the educationof the Prince, theSecretum secretorum. He may have returned toOxford c. 1280, if not before. There, he completed his edition, withnotes and introduction, of this work. In his last work, theCompendium studii theologiae (c. 1292), he repeats some of themain arguments from the 1260s against Richard Rufus of Cornwall. RogerBacon sets out themes in his philosophy of language, philosophy ofnature, and moral philosophy and theology that would influencefourteenth century writers such as Duns Scotus and William of Ockham,among others. Jeremiah Hackett examines the influence of Roger Baconon the philosophy of mind in John Pecham (Hackett 2018c).Bacon’s influence on the fourteenth century has been documentedby Katherine H. Tachau (1988). He is much more important for thephilosophy of the thirteenth and fourteenth centuries than hashitherto been recognized. The editors of Peter of John Olivi on matterhave noted the appropriation by Olivi of Bacon’s teaching onmatter. Doninique Demange and Yael Kedar have demonstrated Peter JohnOlivi’s critical appropriation of Bacon’s theory of Visionand his natural philosophy (Demange & Kedar, 2020). JeremiahHackett (2018a) has suggested that in the early to mid-1260s, Olivimay have been the Iuvenis Johannes, Bacon’s star student.Recently, Mattia Montovani has written a very important study on theimportance of Bacon’s theory of vision for the new Cartesiandiscussions of vision in the early 17th century. It is a study ofmajor significance for the influence of Bacon on early modernphilosophy. (Montovani 2020) As noted above, the newly formedRoger Bacon Research Society will in the near future do muchto further the study of the scientific, philosophical and theologicalworks of Roger Bacon.

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