View source for Roger Bacon

{{Short description|English polymath, philosopher and friar (c.1219/20–c.1292)}}
{{other people}}
{{redirect|Doctor Mirabilis|the 1964 historical novel by James Blish|Doctor Mirabilis (novel) {{!}} ''Doctor Mirabilis'' (novel)}}
{{distinguish|Francis Bacon}}
{{Use British English|date=June 2015}}
{{Use dmy dates|date=June 2015}}
{{Infobox philosopher
| region           = [[Western philosophy]]
| era              = [[Medieval philosophy]]
| name             = Roger Bacon
| honorific_suffix = {{post-nominals|list=[[Order of Friars Minor|OFM]]|size=100%}}
| image            = Roger-bacon-statue.jpg
| caption          = Statue of Bacon at the [[Oxford University Museum of Natural History]]
| other_names      = ''Doctor Mirabilis''
| birth_date       = {{circa|lk=no|1219/20}}
| birth_place      = near [[Ilchester]], Somerset, England
| death_date       = {{circa|lk=no|1292}}{{sfnp|''Encyclopædia Britannica''|1878|p=220}}{{sfnp|''Oxford Dictionary of National Biography''|2004}} (aged about 72/73)
| death_place      = near [[Oxford]], Oxfordshire, England
| alma_mater       = [[University of Oxford]]
| school_tradition = [[Scholasticism]]
| main_interests   = [[Theology]]<br/>[[Natural philosophy]], [[Natural sciences]], [[Chemistry]], [[Biology]], [[engineering]], [[Mathematics]], [[Astronomy]]
| notable_ideas    = [[Experimental science]]
| academic_advisors = [[Adam Marsh]]
}}
'''Roger Bacon''' ({{IPAc-en|ˈ|b|eɪ|k|ən}};<ref>[http://www.collinsdictionary.com/dictionary/english/bacon "Bacon"] {{Webarchive|url=https://web.archive.org/web/20180615032613/http://www.collinsdictionary.com/dictionary/english/bacon |date=15 June 2018 }} entry in ''[[Collins English Dictionary]]''.</ref> {{langx|la|Rogerus}} or ''{{lang|la|Rogerius Baconus, Baconis}}'', also ''{{wikt-lang|la|frater|Frater}} Rogerus''; {{circa|lk=no|1219/20|1292}}), also known by the [[Scholastic accolades|scholastic accolade]] '''''Doctor Mirabilis''''', was a medieval English [[polymath]], [[philosopher]], [[scientist]], [[theologian]] and [[Franciscans|Franciscan]] [[friar]] who placed considerable emphasis on the study of [[nature]] through [[empiricism]]. Intertwining his Catholic faith with scientific thinking, Roger Bacon is considered one of the greatest polymaths of the [[Medieval Period|medieval period]].

In the [[Early modern period|early modern era]], he was regarded as a [[Wizard (paranormal)|wizard]] and particularly famed for the story of his [[History of robots|mechanical]] or [[necromancy|necromantic]] [[brazen head]]. He is credited as one of the earliest European advocates of the modern [[scientific method]], along with his teacher [[Robert Grosseteste]]. Bacon applied the empirical method of [[Ibn al-Haytham]] (Alhazen) to observations in texts attributed to [[Aristotle]]. Bacon discovered the importance of empirical testing when the results he obtained were different from those that would have been predicted by Aristotle.{{sfnp|Ackerman|1978|p=119}}<ref>{{cite web| url = http://www.rogerbaconacademy.net/leadership/who-is-roger-bacon/| title = Who is Roger Bacon?| work = The Roger Bacon Academy| date = 30 June 2011| access-date = 16 October 2019| archive-date = 7 September 2021| archive-url = https://web.archive.org/web/20210907170223/http://www.rogerbaconacademy.net/leadership/who-is-roger-bacon/}}</ref>

His linguistic work has been heralded for its early exposition of a [[universal grammar]], and 21st-century re-evaluations emphasise that Bacon was essentially a medieval thinker, with much of his "experimental" knowledge obtained from books in the [[Scholasticism|scholastic tradition]].{{sfnp|''MSTM''|2005}} He was, however, partially responsible for a revision of the [[medieval university]] curriculum, which saw the addition of [[history of optics|optics]] to the traditional ''{{lang|la|[[quadrivium]]}}''.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}}

Bacon's major work, the {{Lang|la|[[Opus Majus]]}}, was sent to [[Pope Clement IV]] in Rome in 1267 upon the pope's request. Although [[gunpowder]] was [[History of gunpowder|first invented and described in China]], Bacon was the first in Europe to record its formula.
{{TOClimit|3}}

==Life==
Roger Bacon was born in [[Ilchester]] in [[Somerset, England|Somerset]], [[Kingdom of England|England]], in the early 13th century. His birth is sometimes narrowed down to 1210,{{sfn|Hackett (1997), "Life"|p=10}} 1213 or 1214,{{sfnp|James|1928}} 1215{{sfn|Hackett (1997), "Life"|p=11}} or 1220.<ref>{{cite book|title=Complete Dictionary of Scientific Biography|date=2008|publisher=Charles Scribner's Sons|url=http://www.encyclopedia.com/topic/Roger_Bacon.aspx}}</ref> The only source for his birth date is a statement from his 1267 ''{{lang|la|Opus Tertium}}'' that "forty years have passed since I first learned the ''{{lang|la|Alphabetum}}''".{{sfn|Hackett (1997), "Life"|p=9}} The latest dates assume this referred to the [[alphabet]] itself, but elsewhere in the ''{{lang|la|Opus Tertium}}'' it is clear that Bacon uses the term to refer to rudimentary studies, the [[trivium]] or [[quadrivium]] that formed the [[Medieval university#Course of study|medieval curriculum]].{{sfn|Hackett (1997), "Life"|pp=10–11}} His family appears to have been well off.{{sfnp|''Encyclopædia Britannica''|1878|p=218}}

Bacon studied at [[Oxford University|Oxford]].{{refn|group=n|Bacon has been claimed as an alumnus by both [[Merton College, Oxford|Merton]] and [[Brasenose College, Oxford|Brasenose]], despite having attended before the establishment of the collegiate system.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT111 111]}}}} While [[Robert Grosseteste]] had probably left shortly before Bacon's arrival, his work and legacy almost certainly influenced the young scholar{{sfn|Hackett (1997), "Life"|p=10}} and it is possible Bacon subsequently visited him and [[William of Sherwood]] in [[Lincoln, England|Lincoln]].{{sfn|Hackett (1997), "Life"|p=12}} Bacon became a [[Master of Arts|Master]] at Oxford, lecturing on [[Aristotle]]. There is no evidence he was ever awarded a doctorate. (The title ''{{lang|la|Doctor Mirabilis}}'' was a posthumous [[scholastic accolade]].) A caustic cleric named Roger Bacon is recorded speaking before the king at Oxford in 1233.<ref>[[Matthew Paris|Paris]], ''[[Chronica Majora|Chron. Maj.]]'', Vol. III, pp. 244–245.</ref>

[[File:Roger Bacon Wellcome M0005408.jpg|thumb|200px|left|A diorama of Bacon presenting one of his works to the chancellors of [[Paris University]]]]
In 1237 or at some point in the following decade, he accepted an invitation to teach at the [[University of Paris]].{{sfn|Hackett (1997), "Life"|pp=13–14}} While there, he lectured on [[Latin grammar]], [[Term logic|Aristotelian logic]], [[History of arithmetic|arithmetic]], [[History of mathematics|geometry]], and the mathematical aspects of [[History of astronomy|astronomy]] and [[medieval music|music]].{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} His faculty colleagues included [[Robert Kilwardby]], [[Albertus Magnus]], and [[Peter of Spain (logician)|Peter of Spain]],{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=Intro.}} who later became Pope as [[Pope John XXI]].{{sfn|Hackett (1997), "Life"|p=14}} The [[Cornish people|Cornishman]] [[Richard Rufus of Cornwall|Richard Rufus]] was a scholarly opponent.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} In 1247 or soon after, he left his position in Paris.{{sfn|Hackett (1997), "Life"|p=14}}

[[File:Bacon_1867.jpg|thumb|200px|right|A 19th-century engraving of Bacon observing the stars at [[Oxford University|Oxford]]]]
As a private scholar, his whereabouts for the next decade are uncertain{{sfn|Hackett (1997), "Life"|p=15}} but he was likely in Oxford {{circa|lk=no|1248}}–1251, where he met [[Adam Marsh]], and in Paris in 1251.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} He seems to have studied most of the known [[History of science in classical antiquity|Greek]] and [[Physics in the medieval Islamic world|Arabic]] works on [[history of optics|optics]]{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=Intro.}} (then known as "perspective", ''{{lang|la|perspectiva}}''). A passage in the ''{{lang|la|Opus Tertium}}'' states that at some point he took a two-year break from his studies.{{sfn|Hackett (1997), "Life"|p=9}}

By the late 1250s, resentment against [[Henry III of England|the king]]'s preferential treatment of [[House of Lusignan|his émigré Poitevin relatives]] led to [[Henry III of England#Revolution|a coup]] and the imposition of the [[Provisions of Oxford]] and [[Provisions of Westminster|Westminster]], instituting a [[baron]]ial council and more frequent [[Parliament of England|parliaments]]. [[Pope Urban IV]] absolved the king of his oath in 1261 and, after [[Treaty of Lambeth|initial abortive resistance]], [[Simon de Montfort, 6th&nbsp;Earl of Leicester|Simon de Montfort]] led a force, enlarged due to recent crop failures, that prosecuted the [[Second Barons' War]]. Bacon's own family were considered royal partisans:{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT63 63]}} De Montfort's men seized their property{{refn|group=n|Though probably granting it to a partisan of their own cause, rather than razing it to the ground as is sometimes reported.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT63 63]}}}} and drove several members into exile.{{sfnp|''Encyclopædia Britannica''|1878|p=220}}

[[File:Roger Bacon in his observatory at Merton College, Oxford. Oi Wellcome M0001840.jpg|200px|left|thumb|alt=Wellcome Library, oil|[[Ernest Board]]'s portrayal of Bacon in his observatory at [[Merton College, Oxford|Merton College]]]]
In 1256 or 1257, he became a [[friar]] in the [[Franciscans|Franciscan Order]] in either Paris or Oxford, following the example of scholarly English Franciscans such as [[Robert Grosseteste|Grosseteste]] and [[Adam Marsh|Marsh]].{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} After 1260, Bacon's activities were restricted by a statute prohibiting the friars of his order from publishing books or pamphlets without prior approval.{{sfn|Hackett (1997), "Life"|pp=13–17}} He was likely kept at constant menial tasks to limit his time for contemplation{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT62 62]}} and came to view his treatment as an enforced absence from scholarly life.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}}

By the mid-1260s, he was undertaking a search for patrons who could secure permission and funding for his return to Oxford.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT62 62]}} For a time, Bacon was finally able to get around his superiors' interference through his acquaintance with [[Pope Clement IV|Guy de Foulques]], [[Ancient Diocese of Narbonne|bishop of Narbonne]], [[Roman Catholic Suburbicarian Diocese of Sabina-Poggio Mirteto|cardinal of Sabina]], and the [[papal legate]] who negotiated between England's royal and baronial factions.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT63 63]}}

In 1263 or 1264, a message garbled by Bacon's messenger, Raymond of Laon, led Guy to believe that Bacon had already completed a summary of the sciences. In fact, he had no money to research, let alone copy, such a work and attempts to secure financing from his family were thwarted by the Second Barons' War. However, in 1265, Guy was summoned to a conclave at [[Perugia]] that [[Papal conclave|elected]] him {{nowrap|[[Pope Clement IV]]}}.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT64 64]}} William Benecor, who had previously been the courier between [[Henry III of England|Henry III]] and the pope, now carried the correspondence between Bacon and Clement.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT64 64]}} Clement's reply of 22&nbsp;June 1266 commissioned "writings and remedies for current conditions", instructing Bacon not to violate any standing "prohibitions" of his order but to carry out his task in utmost secrecy.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT64 64]}}

While faculties of the time were largely limited to addressing disputes on the known texts of Aristotle, Clement's patronage permitted Bacon to engage in a wide-ranging consideration of the state of knowledge in his era.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} In 1267 or '68, Bacon sent the Pope his ''{{lang|la|[[Opus Majus]]}}'', which presented his views on how to incorporate [[Aristotelian logic]] and [[Greek science#Aristotle|science]] into a new theology, supporting Grosseteste's text-based approach against the "sentence method" then fashionable.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}}

Bacon also sent his ''{{lang|la|Opus Minus}}'', ''{{lang|la|De Multiplicatione Specierum}}'',{{sfn|Hackett (1997), "Life"|pp=17–19}} ''{{lang|la|De Speculis Comburentibus}}'', an optical lens,{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} and possibly other works on [[alchemy]] and [[astrology]].{{sfn|Hackett (1997), "Life"|pp=17–19}}{{refn|group=n|It is still uncertain whether the ''{{lang|la|Opus Tertium}}'' was sent with the others or kept for further revision and development.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}}}} The entire process has been called "one of the most remarkable single efforts of literary productivity", with Bacon composing referenced works of around a million words in about a year.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT67 67]}}

Pope Clement died in 1268 and Bacon lost his protector. The [[Condemnations of 1210–1277|Condemnations of 1277]] banned the teaching of certain philosophical doctrines, including deterministic astrology. Some time within the next two years, Bacon was apparently imprisoned or placed under [[house arrest]]. This was traditionally ascribed to [[Minister General (Franciscan)|Franciscan Minister General]] [[Pope Nicholas IV|Jerome of Ascoli]], probably acting on behalf of the many clergy, monks, and educators attacked by Bacon's 1271 ''{{lang|la|Compendium Studii Philosophiae}}''.{{sfnp|''Encyclopædia Britannica''|1878|p=220}}

Modern scholarship, however, notes that the first reference to Bacon's "imprisonment" dates from eighty years after his death on the charge of unspecified "suspected novelties"<ref>''[[Chronicle of the 24 Generals]]'', late 14th&nbsp;century.</ref>{{sfnp|Maloney|1988|p=[https://books.google.com/books?id=fx84AAAAIAAJ&pg=PA8 8]}} and finds it less than credible.{{sfnp|Lindberg|1995|p=70}} Contemporary scholars who do accept Bacon's imprisonment typically associate it with Bacon's "attraction to contemporary prophesies",{{sfnp|Shank|2009|p=21}} his sympathies for "the radical 'poverty' wing of the Franciscans",{{sfnp|Lindberg|1995|p=70}} interest in certain [[astrology|astrological]] doctrines,{{sfnp|Sidelko|1996}} or generally combative personality{{sfnp|Maloney|1988|p=[https://books.google.com/books?id=fx84AAAAIAAJ&pg=PA8 8]}} rather than from "any scientific novelties which he may have proposed".{{sfnp|Lindberg|1995|p=70}}

Sometime after 1278, Bacon returned to the Franciscan House at Oxford, where he continued his studies{{sfn|Hackett (1997), "Life"|pp=19–20}} and is presumed to have spent most of the remainder of his life. His last dateable writing—the ''{{lang|la|Compendium Studii Theologiae}}''—was completed in 1292.{{sfnp|''Encyclopædia Britannica''|1878|p=220}} He seems to have died shortly afterwards and been buried at Oxford.{{sfnp|''Oxford Dictionary of National Biography''|2004}}<ref>{{Cite journal |url=https://core.ac.uk/download/pdf/60548930.pdf |title=Biography of Roger Bacon |archive-url=https://web.archive.org/web/20190323105257/https://core.ac.uk/download/pdf/60548930.pdf |archive-date=2019-03-23 |website=[[CORE (research service)|CORE]]}}</ref>

==Work==
[[File:Roger Bacon Wellcome M0004484.jpg|thumb|200px|right|A manuscript illustration of Bacon presenting one of his works to the chancellor of the [[University of Paris]]]]
Medieval European philosophy often relied on [[Argument from authority|appeals to the authority]] of [[Church Fathers]] such as [[Augustine of Hippo|St&nbsp;Augustine]], and on works by [[Plato]] and [[Aristotle]] only known at second hand or through Latin translations. By the 13th century, new works and better versions – in [[Arabic]] or in new Latin translations from the Arabic – began to trickle north from [[Al-Andalus|Muslim Spain]]. In Roger Bacon's writings, he upholds Aristotle's calls for the collection of facts before deducing scientific truths, against the practices of his contemporaries, arguing that "thence cometh quiet to the mind".

Bacon also called for reform with regard to [[theology]]. He argued that, rather than training to debate minor philosophical distinctions, theologians should focus their attention primarily on the [[Bible]] itself, learning the languages of its original sources thoroughly. He was fluent in several of these languages and was able to note and bemoan several corruptions of scripture, and of the works of the Greek philosophers that had been mistranslated or misinterpreted by scholars working in Latin. He also argued for the education of theologians in science ("[[natural philosophy]]") and its addition to the [[Medieval university#Course of study|medieval curriculum]].

===''Opus Majus''===
[[File:Roger Bacon optics01.jpg|thumb|200px|[[Optics|Optic]] studies by Bacon]]
{{main|Opus Majus}}
Bacon's 1267 ''Greater Work'', the ''{{lang|la|[[Opus Majus]]}}'',{{refn|group=n|In his works, Bacon also refers to it as his "primary writing" (''{{lang|la|scriptum principale}}'').{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT64 64]}}}} contains treatments of [[mathematics]], [[optics]], [[alchemy]], and [[astronomy]], including theories on the positions and sizes of the [[celestial bodies]]. It is divided into seven sections: "The Four General Causes of Human Ignorance" (''{{lang|la|Causae Erroris}}''), "The Affinity of Philosophy with Theology" (''{{lang|la|Philosophiae cum Theologia Affinitas}}''), "On the Usefulness of Grammar" (''{{lang|la|De Utilitate Grammaticae}}''),<ref name="baconI3">{{harvp|Bacon|1897|loc=[https://archive.org/stream/opusmajusofroger01baco Vol.&nbsp;I]}} & [[#{{harvid|Bridges|1900}}|(1900)]], [https://archive.org/stream/b24975655_0003 Vol.&nbsp;III].</ref> "The Usefulness of Mathematics in Physics" (''{{lang|la|Mathematicae in Physicis Utilitas}}''),<ref name=baconI4/> "[[#Optics|On the Science of Perspective]]" (''{{lang|la|De Scientia Perspectivae}}''), "On Experimental Knowledge" (''{{lang|la|De Scientia Experimentali}}''), and "A Philosophy of Morality" (''{{lang|la|Moralis Philosophia}}'').<ref name="baconII5">{{harvp|Bacon|1897|loc=[https://archive.org/stream/opusmajusofroger02bacouoft Vol.&nbsp;II] }}</ref>

It was not intended as a complete work but as a "persuasive preamble" (''{{lang|la|persuasio praeambula}}''), an enormous proposal for a reform of the [[medieval university]] curriculum and the establishment of a kind of library or encyclopedia, bringing in experts to compose a collection of definitive texts on these subjects.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT66 66]}} The new subjects were to be "perspective" (i.e., [[optics]]), "astronomy" (inclusive of [[astronomy]] proper, [[astrology]], and the [[geography]] necessary to use them), "weights" (likely some treatment of [[mechanics]] but this section of the ''{{lang|la|Opus Majus}}'' has been lost), [[alchemy]], [[agriculture]] (inclusive of [[botany]] and [[zoology]]), [[medicine]], and "[[experiment]]al science", a [[philosophy of science]] that would guide the others.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT66 66]}} The section on geography was allegedly originally ornamented with a [[history of cartography|map]] based on ancient and Arabic computations of longitude and latitude, but has since been lost. His (mistaken) arguments supporting the idea that dry land formed the larger proportion of the globe were apparently similar to those which later guided [[Christopher Columbus|Columbus]].<ref name="worthy">{{harvp|''Worthies''|1828|pp=[https://books.google.com/books?id=QjhkAAAAcAAJ&pg=PA45 45–46]}}</ref>

In this work Bacon criticises his contemporaries [[Alexander of Hales]] and [[Albertus Magnus]], who were held in high repute despite having only acquired their knowledge of [[Aristotle]] at second hand during their preaching careers.{{sfn|Hackett (1997), "Classification"|pp=49–52}}{{sfnp|Hackett|1980}} Albert was received at Paris as an authority equal to Aristotle, [[Avicenna]] and [[Averroes]],{{sfnp|Easton|1952|pp=210–219}} a situation Bacon decried: "never in the world [had] such monstrosity occurred before".{{sfnp|LeMay|1997|pp=40–41}}

In Part I of the ''Opus Majus'' Bacon recognises some philosophers as the ''Sapientes'', or gifted few, and saw their knowledge in philosophy and theology as superior to the ''vulgus philosophantium'', or common herd of philosophers. He held Islamic thinkers between 1210 and 1265 in especially high regard calling them "both philosophers and sacred writers" and defended the integration of philosophy from apostate philosopher of the Islamic world into Christian learning.{{sfnp|Hackett|2011|pp=151–166}}<gallery>
File:Roger Bacon-2.jpg|alt=|Spine of a 1750 edition of ''Opus majus''
File:Bacon - Opus maius, 1750 - 4325246.tif|alt=|Title page of 1750 edition of ''Opus majus''
File:Roger Bacon-1.jpg|alt=|First page of 1750 edition of ''Opus majus''
</gallery>

====Calendrical reform====
{{hatnote|Main: [[Calendrical reform#Julian and Gregorian reforms|Calendrical reform]] and [[Gregorian calendar#Gregorian reform|Gregorian calendar]]}}
In Part IV of the ''{{lang|la|Opus Majus}}'', Bacon proposed a [[Calendar reform|calendrical reform]] similar to the later [[Gregorian calendar#Gregorian reform|system]] introduced in 1582 under [[Pope Gregory XIII]].<ref name=baconI4/> Drawing on [[Ancient Greek astronomy|ancient Greek]] and [[Astronomy in the medieval Islamic world|medieval Islamic]] astronomy recently introduced to western Europe via Spain, Bacon continued the work of [[Robert Grosseteste]] and criticised the then-current [[Julian calendar]] as "intolerable, horrible, and laughable".

It had become apparent that [[Eudoxus of Cnidus|Eudoxus]] and [[Sosigenes of Alexandria|Sosigenes]]'s assumption of a year of 365¼ days was, over the course of centuries, too inexact. Bacon charged that this meant the [[computus|computation of Easter]] had shifted forward by 9 days since the [[First Council of Nicaea]] in 325.<ref name=dunkin>{{citation |last=Duncan |first=David Ewing |author-mask=Duncan |title=The Calendar |date=2011 |pages=1–2 }}</ref> His proposal to drop one day every 125 years<ref name=baconI4>{{harvp|Bacon|1897|loc=[https://archive.org/details/opusmajusrogerb01bridgoog Vol.&nbsp;I], [https://archive.org/stream/opusmajusrogerb01bridgoog#page/n293/mode/2up Pt.&nbsp;IV] }}</ref>{{sfnp|North|1983|pp=75, 82–84}} and to cease the observance of fixed [[equinox]]es and [[solstice]]s<ref name=dunkin/> was not acted upon following the death of [[Pope Clement IV]] in 1268. The eventual [[Gregorian calendar]] drops one day from the first three centuries in each set of 400 years.

====Optics====
[[File:Optics from Roger Bacon's De multiplicatone specierum.jpg|200px|thumb|right|Bacon's diagram of light being refracted by a spherical container of water]]
{{see also|History of optics}}
In Part V of the ''{{lang|la|[[Opus Majus]]}}'', Bacon discusses [[visual system|physiology of eyesight]] and the anatomy of the [[human eye|eye]] and the [[human brain|brain]], considering [[light]], distance, position, and size, direct and [[reflection (physics)|reflected]] vision, [[refraction]], [[mirror]]s, and [[lens (optics)|lenses]].<ref name=baconII5/> His treatment was primarily oriented{{clarify|date=October 2025}} by the Latin translation of [[Ibn al-Haytham|Alhazen]]'s ''[[Book of Optics]]''. He also draws heavily on [[Eugene of Palermo]]'s Latin translation of the Arabic translation of [[Claudius Ptolemy|Ptolemy]]'s ''[[Optics (Ptolemy)|Optics]]''; on [[Robert Grosseteste]]'s work based on [[Al-Kindi]]'s ''[[Optics (Al-Kindi)|Optics]]'';{{sfnp|Ackerman|1978|p=119}}<ref>{{citation |author=Ptolemy |title=Optics |publisher=(Smith trans.) |url=https://books.google.com/books?id=mhLVHR5QAQkC |date=1996 |page=[https://books.google.com/books?id=mhLVHR5QAQkC&pg=PA58 58] |author-link=Claudius Ptolemy |isbn=9780871698629 }}</ref> and, through Alhazen ([[Ibn al-Haytham]]), on [[Ibn Sahl (mathematician)|Ibn Sahl]]'s work on [[dioptrics]].{{sfnp|El-Bizri|2005}}

====Gunpowder====
[[File:137-ROGER BACON DISCOVERS GUNPOWDER.jpg|thumb|right|200px|"Roger Bacon discovers gunpowder", "whereby [[Guy Fawkes]] was made possible",<ref>{{citation |last=Nye |first=Bill |author-link=Edgar Wilson Nye |display-authors=0 |url=https://archive.org/details/billnyescomichis00nyebrich |title=Bill Nye's Comic History of England |date=1896 |page=[https://archive.org/stream/billnyescomichis00nyebrich#page/136/mode/2up 136] |publisher=Chicago, Thompson and Thomas }}</ref> an image from ''[[Edgar Wilson Nye|Bill Nye]]'s Comic History of England''<ref>{{citation |last=Nye |first=Bill |author-link=Edgar Wilson Nye |display-authors=0 |url=https://archive.org/details/billnyescomichis00nyebrich |title=Bill Nye's Comic History of England |date=1896 |page=[https://archive.org/stream/billnyescomichis00nyebrich#page/136/mode/2up 137] |publisher=Chicago, Thompson and Thomas }}</ref>]]
A passage in the ''{{lang|la|Opus Majus}}'' and another in the ''{{lang|la|Opus Tertium}}'' are usually taken as the first European descriptions of a mixture containing the essential ingredients of [[gunpowder]]. [[J. R. Partington|Partington]] and others have come to the conclusion that Bacon most likely witnessed at least one demonstration of [[Yuan dynasty|Chinese]] [[firecracker]]s, possibly obtained by Franciscans—including Bacon's friend [[William of Rubruck]]—who visited the [[Mongol Empire]] during this period.{{sfnp|Needham|Lu|Wang|1987|pp=48–50}}{{refn|group=n|"Europeans were prompted by all this to take a closer interest in happenings far to the east. Four years after the invasion of 1241, the pope sent an ambassador to the Great Khan's capital in Mongolia. Other travellers followed later, of whom the most interesting was [[William of Rubruck]] (or Ruysbroek). He returned in 1257, and in the following year there are reports of experiments with gunpowder and rockets at Cologne. Then a friend of William of Rubruck, Roger Bacon, gave the first account of gunpowder and its use in fireworks to be written in Europe. A form of gunpowder had been known in China since before AD 900, and as mentioned earlier{{nbsp}}... Much of this knowledge had reached the Islamic countries by then, and the saltpetre used in making gunpowder there was sometimes referred to, significantly, as 'Chinese snow'."{{sfnp|Pacey|1991|p=[https://books.google.com/books?id=X7e8rHL1lf4C&pg=PA45 45]}}}} The most telling passage reads:
<blockquote>We have an example of these things (that act on the senses) in [the sound and fire of] that children's toy which is made in many [diverse] parts of the world; i.e. a device no bigger than one's thumb. From the violence of that salt called saltpetre [together with sulphur and willow charcoal, combined into a powder] so horrible a sound is made by the bursting of a thing so small, no more than a bit of parchment [containing it], that we find [the ear assaulted by a noise] exceeding the roar of strong thunder, and a flash brighter than the most brilliant lightning.{{sfnp|Needham|Lu|Wang|1987|pp=48–50}} </blockquote>

At the beginning of the 20th century, [[Henry William Lovett Hime]] of the [[Royal Artillery]] published the theory that Bacon's ''{{lang|la|Epistola}}'' contained a [[cryptogram]] giving a recipe for the gunpowder he witnessed.<ref>{{cite EB1911 |last=Hodgkinson |first=William Richard Eaton |wstitle=Gunpowder |mode=cs2}}</ref> The theory was criticised by [[Lynn Thorndike|Thorndike]] in a 1915 letter to ''[[Science (journal)|Science]]''{{sfnp|Thorndike|1915}} and several books, a position joined by [[M. M. Pattison Muir|Muir]],{{sfnp|Stillman|2003|p=202}} [[John Maxson Stillman]],{{sfnp|Stillman|2003|p=202}} [[Robert Steele (medievalist)|Steele]],{{sfnp|Steele|1928}} and [[George Sarton|Sarton]].{{sfnp|Sarton|1975|p=958}} [[Joseph Needham|Needham]] et al. concurred with these earlier critics that the additional passage did not originate with Bacon{{sfnp|Needham|Lu|Wang|1987|pp=48–50}} and further showed that the proportions supposedly deciphered (a 7:5:5 ratio of [[Niter|saltpetre]] to [[charcoal]] to [[Sulfur|sulphur]]) as not even useful for firecrackers, burning slowly with a great deal of smoke and failing to ignite inside a gun barrel.{{sfnp|Needham|Lu|Wang|1987|loc=Vol.&nbsp;V, Pt.&nbsp;7, p.&nbsp;358}} The ~41% [[nitrate]] content is too low to have explosive properties.{{sfnp|Hall|1999|p=xxiv}}

[[File:Friar Bacon.png|thumb|left|200px|Friar Bacon in his study{{sfnp|Baldwin|1905|p=64}}]]

===''Secret of Secrets''===
{{main|Secretum Secretorum}}
Bacon attributed the ''Secret of Secrets'' (''{{lang|la|Secretum Secretorum}}'') ({{langx|ar|Sirr al-ʿasrar}}<!--sic-->), to [[Aristotle]], thinking that he had composed it for [[Alexander the Great]]. Bacon produced an edition of [[Philip of Tripoli]]'s Latin translation, complete with his own introduction and notes; and his writings of the 1260s and 1270s cite it far more than his contemporaries did. This led [[Stewart C. Easton|Easton]]{{sfnp|Easton|1952}} and others, including [[Robert Steele (medievalist)|Robert Steele]],{{sfnp|Williams|1997}} to argue that the text spurred Bacon's own transformation into an experimentalist. (Bacon never described such a decisive impact himself.){{sfnp|Williams|1997}} The dating of Bacon's edition of the ''Secret of Secrets'' is a key piece of evidence in the debate, with those arguing for a greater impact giving it an earlier date;{{sfnp|Williams|1997}} but it certainly influenced the elder Bacon's conception of the political aspects of his work in the sciences.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}}

===Alchemy===
[[File:Roger Bacon conducting an alchemical experiment in a vaulted Wellcome V0025604.jpg|thumb|200px|alt=J. Nasmyth (1845)|A 19th-century etching of Bacon conducting an alchemical experiment]]
Bacon has been credited with a number of [[alchemy|alchemical]] texts.{{sfnp|Bartlett|2008|p=124}}

The ''Letter on the Secret Workings of Art and Nature and on the Vanity of Magic'' (''{{lang|la|Epistola de Secretis Operibus Artis et Naturae et de Nullitate Magiae}}''),{{sfnp|Brewer|1859|pp=[http://gallica.bnf.fr/ark:/12148/bpt6k50167j/f631.item.zoom 523 ff]}} also known as ''On the Wonderful Powers of Art and Nature'' (''{{lang|la|De Mirabili Potestate Artis et Naturae}}''), a likely-forged letter to an unknown "William of Paris", dismisses practices such as [[necromancy]]{{sfnp|Zambelli|2007|pp=48–49}} but contains most of the alchemical formulae attributed to Bacon,{{sfnp|Bartlett|2008|p=124}} including one for a [[philosopher's stone]]{{sfnp|Newman|1997|pp=328–329}} and another possibly for [[gunpowder]].{{sfnp|Needham|Lu|Wang|1987|pp=48–50}} It also includes several passages about [[history of flight|hypothetical flying machines]] and [[history of submarines|submarines]], attributing their first use to [[Alexander the Great]].{{sfnp|Gray|2011|pp=185–186}} ''On the Vanity of Magic'' or ''The Nullity of Magic'' is a [[debunking]] of esoteric claims in Bacon's time, showing that they could be explained by natural phenomena.{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA132 132]}}

He wrote on the medicine of [[Galen]], referring to the translations of [[Avicenna]]. He believed that the medicine of Galen belonged to an ancient tradition passed through [[Chaldea]]ns, [[Greeks]] and [[Arab]]s.<ref>{{cite journal|first1=David Eugene|last1=Smith|author-link1=David Eugene Smith|title=Medicine and Mathematics in the Sixteenth Century|pmc=7927718|pmid= 33943138|journal=Ann Med Hist.|date=July 1, 1917|volume= 1|issue=2|pages=125–140|oclc=12650954}} (here cited p. 126).</ref> Although he provided a negative image of [[Hermes Trismegistus]], his work was influenced by Hermetic thought{{dubious|date=December 2023}}{{clarify|date=December 2023}}.<ref>{{cite journal|first1=George|last1=Molland|url=|title=Roger Bacon and the Hermetic Tradition in Medieval Science|journal=Vivarium|volume=XXXI|issue= 1|year=1993|pages= 140–160|jstor=42569882|publisher=Brill|doi=10.1163/156853493X00123|oclc=812885091|issn=0042-7543}}</ref> Bacon's endorsement of Hermetic philosophy is evident, as his citations of the alchemical literature known as the Secretum Secretorum made several appearances in the Opus Majus. The Secretum Secretorum contains knowledge about the Hermetic [[Emerald Tablet]], which was an integral component of alchemy, thus proving that Bacon's version of alchemy was much less secular, and much more spiritual than once interpreted. The importance of Hermetic philosophy in Bacon's work is also evident through his citations of classic Hermetic literature such as the Corpus Hermeticum. Bacon's citation of the Corpus Hermeticum, which consists of a dialogue between Hermes and the pagan deity [[Asclepius]], proves that Bacon's ideas were much more in line with the spiritual aspects of alchemy rather than the scientific aspects. However, this is somewhat paradoxical as what Bacon was specifically trying to prove in the Opus Majus and subsequent works, was that spirituality and science were the same entity. Bacon believed that by using science, certain aspects of spirituality such as the attainment of "Sapientia" or "Divine Wisdom" could be logically explained using tangible evidence. Bacon's Opus Majus was first and foremost, a compendium of sciences which he believed would facilitate the first step towards "Sapientia". Bacon placed considerable emphasis on alchemy and even went so far as to state that alchemy was the most important science. The reason why Bacon kept the topic of alchemy vague for the most part, is due to the need for secrecy about esoteric topics in England at the time as well as his dedication to remaining in line with the alchemical tradition of speaking in symbols and metaphors.<ref>{{cite book|first1=Victoria |last1=Tobes |url=https://scholarsarchive.library.albany.edu/cgi/viewcontent.cgi?article=1017&context=history_honors|title=Roger Bacon: The Christian, the Alchemist, the Enigma (History Honors Program. 12)|pages=29–30|format=PDF|quote="the Creator may be known through the knowledge of the creature{{nbsp}}... to whom service may be rendered{{nbsp}}... in the beauty of morals".|publisher=University at Albany, State University of New York|year=2019|archive-url=https://web.archive.org/web/20200321100704/https://scholarsarchive.library.albany.edu/cgi/viewcontent.cgi?article=1017&context=history_honors|archive-date=March 21, 2020|url-status=live}} (degree thesis)</ref>

===Linguistics===
{{main|Summa Grammatica}}
{{see also|Universal grammar}}
Bacon's early linguistic and logical works are the ''Overview of Grammar'' (''[[Summa Grammatica]]''), ''{{lang|la|Summa de Sophismatibus et Distinctionibus}}'', and the ''{{lang|la|Summulae Dialectices}}'' or ''{{lang|la|Summulae super Totam Logicam}}''.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} These are mature but essentially conventional presentations of Oxford and Paris's terminist and pre-[[modistae|modist]] logic and grammar.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} His later work in linguistics is much more idiosyncratic, using terminology and addressing questions unique in his era.<ref name=hovd1>{{harvp|Hovdhaugen|1990|p=[https://books.google.com/books?id=8UxAAAAAQBAJ&pg=PA124 121–122]}}.</ref>

In his ''[[Grammatica Graeca|Greek]]'' and ''[[Grammatica Hebraica|Hebrew Grammars]]'' (''{{lang|la|Grammatica Graeca}}'' and ''{{lang|la|Hebraica}}''), in his work "On the Usefulness of Grammar" (Book III of the ''{{lang|la|[[#Opus Majus|Opus Majus]]}}''), and in his ''Compendium of the Study of Philosophy'',<ref name=hovd1/> Bacon stresses the need for scholars to know several languages.<ref name=hovd8/> Europe's vernacular languages are not ignored—he considers them useful for practical purposes such as [[medieval trade|trade]], [[Christian proselytism|proselytism]], and [[government in the High Middle Ages|administration]]—but Bacon is mostly interested in his era's [[languages of science]] and religion: [[Arabic]], [[Greek language|Greek]], [[Hebrew language|Hebrew]] and [[Medieval Latin|Latin]].<ref name=hovd8>{{harvp|Hovdhaugen|1990|p=[https://books.google.com/books?id=8UxAAAAAQBAJ&pg=PA128 128]}}.</ref>

Bacon is less interested in a full practical mastery of the other languages than on a theoretical understanding of their grammatical rules, ensuring that a Latin reader will not misunderstand passages' [[authorial intent|original meaning]].<ref name=hovd8/> For this reason, his treatments of Greek and Hebrew grammar are not isolated works on their topic<ref name=hovd8/> but contrastive grammars treating the aspects which influenced Latin or which were required for properly understanding Latin texts.<ref name=hovd9>{{harvp|Hovdhaugen|1990|p=[https://books.google.com/books?id=8UxAAAAAQBAJ&pg=PA129 129]}}.</ref> He pointedly states, "I want to describe Greek grammar for the benefit of Latin speakers".<ref name=hovd3/>{{refn|group=n|Latin: ''{{lang|la|Cupiens igitur exponere gramaticam grecam ad vtilitatem latinorum}}''.<ref name=hovd3>{{harvp|Hovdhaugen|1990|p=[https://books.google.com/books?id=8UxAAAAAQBAJ&pg=PA123 123]}}.</ref>}} It is likely only this limited sense which was intended by Bacon's boast that he [[Language education|could teach an interested pupil a new language]] within three days.<ref name=hovd9/>{{refn|group=n|It has been claimed that the copies of Bacon's grammars which have survived was not their final form, but [[Eva Hovdhaugen|Hovdhaugen]] considers that—even if that were the case—the final form would have been similar in scope to the surviving texts and mostly focused on improving a Latinate reader's understanding of texts in translation.<ref name=hovd9/>}}

Passages in the ''Overview'' and the Greek grammar have been taken as an early exposition of a [[universal grammar]] underlying all [[human]] [[language]]s.<ref name=lawman>{{harvp|Murphy|1974|p=[https://books.google.com/books?id=8B5z0MiRnJ8C&pg=PA153 153]}}.</ref> The Greek grammar contains the tersest and most famous exposition:<ref name=lawman/>
{{blockquote|Grammar is one and the same in all languages, substantially, though it may vary, accidentally, in each of them.{{refn|[[Edmond Nolan|Nolan]],{{sfnp|Nolan & al.|1902|p=27}} cited in [[James J. Murphy|Murphy]].{{sfnp|Murphy|1974|p=[https://books.google.com/books?id=8B5z0MiRnJ8C&pg=PA154 154]}}}}{{refn|group=n|[[Latin]]: ''{{lang|la|...grammatica vna et eadem est secundum substanciam in omnibus linguis, licet accidentaliter varietur...}}.''<ref name=hovd3/>}}}}
However, Bacon's lack of interest in studying a literal [[grammar]] underlying the languages known to him and his numerous works on linguistics and comparative linguistics has prompted [[Eva Hovdhaugen|Hovdhaugen]] to question the usual literal translation of Bacon's ''{{lang|la|grammatica}}'' in such passages.<ref name=hovd7/> She notes the ambiguity in the Latin term, which could refer variously to the structure of language, to its description, and to the science underlying such descriptions: i.e., [[linguistics]].<ref name=hovd7>{{harvp|Hovdhaugen|1990|p=[https://books.google.com/books?id=8UxAAAAAQBAJ&pg=PA127 127–128]}}.</ref>

===Other works===
[[File:Roger Bacon Wellcome M0004130.jpg|thumb|right|200px|A portrait of Roger Bacon from a 15th-century edition of ''{{lang|la|De Retardatione}}''<ref>MS Bodl. 211.</ref>]]
[[File:Roger Bacon page from book.jpg|right|200px|thumb|The first page of the letter from Bacon to {{nowrap|[[Pope Clement IV|Clement IV]]}} introducing his ''{{lang|la|Opus Tertium}}''{{sfnp|Brewer|1859|loc=[https://books.google.com/books?id=wMUKAAAAYAAJ&pg=PR9-IA6 Plate III]}}]]

Bacon states that his ''Lesser Work'' (''{{lang|la|Opus Minus}}'') and ''Third Work'' (''{{lang|la|Opus Tertium}}'') were originally intended as summaries of the ''{{lang|la|Opus Majus}}'' in case it was lost in transit.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT66 66]}} [[Stewart C. Easton|Easton]]'s review of the texts suggests that they became separate works over the course of the laborious process of creating a [[Foul papers|fair copy]] of the ''{{lang|la|Opus Majus}}'', whose half-million words were copied by hand and apparently greatly revised at least once.{{sfnp|Clegg|2003|p=[https://books.google.com/books?id=IiqeBAAAQBAJ&pg=PT67 67]}}

Other works by Bacon include his "Tract on the Multiplication of Species" (''{{lang|la|Tractatus de Multiplicatione Specierum}}''),{{sfnp|Bacon|1897|p=[https://archive.org/stream/opusmajusofroger02bacouoft#page/404/mode/2up 405–552]}} "On Burning Lenses" (''{{lang|de|De Speculis Comburentibus}}''), the ''{{lang|la|Communia Naturalium}}'' and ''{{lang|la|Mathematica}}'', the "Compendium of the Study of Philosophy" and "of Theology" (''{{lang|la|Compendium Studii Philosophiae}}'' and ''{{lang|la|Theologiae}}''), and his ''Computus''.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§2}} The "Compendium of the Study of Theology", presumably written in the last years of his life, was an anticlimax: adding nothing new, it is principally devoted to the concerns of the 1260s.

===Apocrypha===
''[[The Mirror of Alchimy]]''<!--sic--> (''{{lang|la|Speculum Alchemiae}}''), a short treatise on the origin and composition of metals, is traditionally credited to Bacon.<ref>{{citation |last=Zwart |first=Hub |author-mask=Zwart |title=Understanding Nature |date=2008 |page=236 }}</ref> It espouses the Arabian theory of [[Mercury (element)|mercury]] and [[Sulfur|sulphur]] forming the other metals, with vague allusions to [[Alchemy|transmutation]]. [[John Maxson Stillman|Stillman]] opined that "there is nothing in it that is characteristic of Roger Bacon's style or ideas, nor that distinguishes it from many unimportant alchemical lucubrations of anonymous writers of the thirteenth to the sixteenth centuries", and [[M. M. Pattison Muir|Muir]] and [[Edmund Oscar von Lippmann|Lippmann]] also considered it a [[Pseudepigrapha|pseudepigraph]].{{sfnp|Stillman|2003|p=271}}

The cryptic [[Voynich manuscript]] has been attributed to Bacon by various sources, including by its first recorded owner,{{sfnp|Newbold & al.|1928}}{{sfnp|Goldstone & al.|2005}}<ref>{{citation |url=https://query.nytimes.com/gst/fullpage.html?res=9C03E4DD103AF933A15751C0A9639C8B63&pagewanted=1 |contribution=The Bacon Code |last=Steele |first=Margaret Farley |author-mask=Steele |date=20 Feb 2005 |title=NY Times }}</ref> but [[history of science|historians of science]] [[Lynn Thorndike]] and [[George Sarton]] dismissed these claims as unsupported,<ref>{{citation |last=Thorndike |first=Lynn |author-mask=Thorndike |author-link=Lynn Thorndike |contribution=Review of ''The Cipher of Roger Bacon'' |title=The American Historical Review |volume=34, No.&nbsp;2 |issue=2 |pages=317–319 |date=Jan 1928 |jstor=1838571 |title-link=The American Historical Review |publisher=Oxford University Press, American Historical Association |doi=10.2307/1838571 }}</ref><ref>{{citation |last=Sarton |first=George |author-mask=Sarton |author-link=George Sarton |contribution=Review of ''The Cipher of Roger Bacon'' |title=Isis |volume=11, No.&nbsp;1 |issue=1 |pages=141–145 |jstor=224770 |date=Sep 1928 |doi=10.1086/346365 |publisher=The University of Chicago Press, The History of Science Society }}</ref><ref>{{citation |last=Foster |first=Benjamin R. |author-mask=Foster |editor-last=Garraty |editor-first=John Arthur |editor2-last=Carnes |editor2-first=Mark Christopher |display-editors=0 |title=American National Biography |contribution=William Romaine Newbold |date=1999 |title-link=American National Biography }}</ref> and the [[vellum]] of the manuscript has since been dated to the 15th century.<ref>{{cite web|title=UA Experts Determine Age of Book 'Nobody Can Read'|url=http://uanews.arizona.edu/story/ua-experts-determine-age-of-book-nobody-can-read|publisher=University of Arizona|access-date=3 December 2015|date=9 February 2011}}</ref>

==Legacy==
[[File:Friar Bacon's Brazen Head.png|thumb|right|200px|A woodcut from [[Robert Greene (dramatist)|Robert Greene]]'s [[Friar Bacon and Friar Bungay|play]] displaying the [[brazen head]] pronouncing "Time is. Time was. Time is past."]]
[[File:Roger Bacons Study in Oxford.jpg|thumb|200px|"Friar Bacon's Study" in [[Oxford]]. By the late 18th century this study on [[Folly Bridge]] had become a place of pilgrimage for scientists, but the building was pulled down in 1779 to allow for road widening.{{sfnp|Fauvel & al.|2000|p=2}}]]
[[File:Roger Bacon Plaque.jpg|thumb|right|200px|The [[Westgate Oxford|Westgate]] plaque at Oxford]]
Bacon was largely ignored by his contemporaries in favour of other scholars such as [[Albertus Magnus]], [[Bonaventure]], and [[Thomas Aquinas]],{{sfnp|''Encyclopædia Britannica''|1878|p=218}} although his works were studied by Bonaventure, [[John Pecham]], and [[Peter of Limoges]], through whom he may have influenced [[Raymond Lull]].{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=Intro.}} He was also partially responsible for the addition of [[history of optics|optics]] (''{{lang|la|perspectiva}}'') to the [[medieval university]] [[medieval university#curriculum|curriculum]].{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}}

By the [[early modern period]], the English considered him the epitome of a wise and subtle possessor of [[Western esotericism|forbidden knowledge]], a [[Faust]]-like magician who had tricked the [[Devil (Christianity)|devil]] and so was able to go to [[heaven (Christianity)|heaven]]. Of these legends, one of the most prominent was that he created a [[Brazen head|talking brazen head]] which could answer any question. The story appears in the anonymous 16th-century account of ''The Famous Historie of Fryer Bacon'',{{refn|group=n|Although the manuscript was circulated in by {{circa|lk=no|1555}}, it was not published until 1627.{{sfnp|''Fryer Bacon''|1627}} It was republished in the mid-19th century.<ref>{{citation |editor-last=Thomas |editor-first=William J. |display-editors=0 |title=Early English Prose Romances: With Bibliographical and Historical Introductions |location=London |publisher=Nattali & Bond |date=1858 }}</ref>}} in which Bacon speaks with a demon but causes the head to speak by "the continuall fume of the six hottest Simples",<ref name=fryer>{{harvp|''Fryer Bacon''|1627}}.</ref> testing his theory that speech is caused by "an effusion of vapors".{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA134 134]}}

Around 1589, [[Robert Greene (dramatist)|Robert Greene]] adapted the story for the stage as ''[[The Honorable Historie of Frier Bacon and Frier Bongay]]'',{{sfnp|Greene|1594}}{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA129 129]}}{{sfnp|Kavey|2007|pp=38–39}} one of the most successful [[English Renaissance theatre|Elizabethan comedies]].{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA129 129]}} As late as the 1640s, [[Thomas Browne]] was still complaining that "Every ear is filled with the story of Frier Bacon, that made a brazen head to speak these words, ''Time is''".<ref name=girlscout>[[Thomas Browne|Browne]], ''[[Pseudodoxia Epidemica|Pseud. Epid.]]'', [http://penelope.uchicago.edu/pseudodoxia/pseudo717.html#brazenhead Bk.&nbsp;VII, Ch.&nbsp;xvii, §7.] {{Webarchive|url=https://web.archive.org/web/20230108104636/http://penelope.uchicago.edu/pseudodoxia/pseudo717.html#brazenhead |date=8 January 2023 }}</ref> Greene's Bacon spent seven years creating a brass head that would speak "strange and uncouth aphorisms"<ref>[[Robert Greene (dramatist)|Greene]], ''[[Friar Bacon & Friar Bungay|Fr. Bacon]]'', iii.168.</ref> to enable him to encircle [[Great Britain|Britain]] with a wall of brass that would make it impossible to conquer.

Unlike his source material, Greene does not cause his head to operate by natural forces but by "[[necromancy|nigromantic]]<!--sic--> charms" and "the enchanting forces of the [[devil (Christianity)|devil]]":<ref>[[Robert Greene (dramatist)|Greene]], ''[[Friar Bacon & Friar Bungay|Fr. Bacon]]'', xi.15 & 18.</ref> i.e., by entrapping a [[ghost|dead spirit]]{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA134 134]}} or [[hobgoblin]].<ref>[[Robert Greene (dramatist)|Greene]], ''[[Friar Bacon & Friar Bungay|Fr. Bacon]]'', xi.52.</ref> Bacon collapses, exhausted, just before his device comes to life and announces "Time is", "Time was", and "Time is Past"<ref>[[Robert Greene (dramatist)|Greene]], ''[[Friar Bacon & Friar Bungay|Fr. Bacon]]'', ix.53–73.</ref> before being destroyed in spectacular fashion: the [[stage direction]] instructs that "''a lightening flasheth forth, and a hand appears that breaketh down the Head with a hammer''".<ref>[[Robert Greene (dramatist)|Greene]], ''[[Friar Bacon & Friar Bungay|Fr. Bacon]]'', ix.72.</ref>

A [[brazen head|necromantic head]] was ascribed to [[Pope Sylvester&nbsp;II]] as early as the 1120s,<ref>[[William of Malmesbury|Malmesbury]], ''[[Chronicle of the Kings of England|Chron.]]'', [https://books.google.com/books?id=rTpLAwAAQBAJ&pg=PA181  Bk.&nbsp;II., Ch. x., p.&nbsp;181].</ref>{{refn|group=n|[[William of Malmesbury|Malmesbury]] even notes that "probably some may regard all this as a fiction, because the vulgar are used to undermine the fame of scholars, saying that the man who excels in any admirable science, holds converse with the devil"<ref>[[William of Malmesbury|Malmesbury]], ''[[Chronicle of the Kings of England|Chron.]]'', [https://books.google.com/books?id=rTpLAwAAQBAJ&pg=PA174  Bk.&nbsp;II., Ch. x., p.&nbsp;174].</ref> but professes himself willing to believe the stories about [[Pope Sylvester II|Sylvester]] because of the (spurious) accounts he had of the pope's "shameful end".<ref>[[William of Malmesbury|Malmesbury]], ''[[Chronicle of the Kings of England|Chron.]]'', [https://books.google.com/books?id=rTpLAwAAQBAJ&pg=PA175  Bk.&nbsp;II., Ch. x., p.&nbsp;175].</ref>}} but [[Thomas Browne|Browne]] considered the legend to be a misunderstanding of a passage in [[Petrus Bonus|Peter the Good]]'s {{circa|lk=no|1335}} ''[[Petrus Bonus|Precious Pearl]]'' where the negligent alchemist misses the birth of his creation and loses it forever.<ref name=girlscout/> The story may also preserve the work by Bacon and his contemporaries to construct clockwork [[armillary sphere]]s.{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA138 138]}} Bacon had praised a "self-activated working model of the heavens" as "the greatest of all things which have been devised".<ref>Bacon, ''[[De Nullitate Magiae|De Null. Mag.]]'', 29.</ref>

As early as the 16th century, [[natural philosophy|natural philosophers]] such as [[Giordano Bruno|Bruno]], [[John Dee|Dee]]{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA132 132–4]}} and [[Francis Bacon]]{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}} were attempting to rehabilitate Bacon's reputation and to portray him as a scientific pioneer who had avoided the petty bickering of his contemporaries to attempt a rational understanding of nature. By the 19th century, commenters following [[William Whewell|Whewell]]{{sfnp|Whewell|1858}}{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}} considered that "Bacon{{nbsp}}... was not appreciated in his age because he was so completely in advance of it; he is a 16th- or 17th-century philosopher, whose lot has been by some accident cast in the 13th century".{{sfnp|''Encyclopædia Britannica''|1878|p=218}} His assertions in the ''{{lang|la|Opus Majus}}'' that "theories supplied by reason should be verified by sensory data, aided by instruments, and corroborated by trustworthy witnesses"<ref>Bacon, ''Opus Majus'', Bk.&VI.</ref> were (and still are) considered "one of the first important formulations of the [[scientific method]] on record".{{sfnp|Borlik|2011|p=[https://books.google.com/books?id=c_ShAgAAQBAJ&pg=PA132 132]}}

This idea that Bacon was a modern experimental scientist reflected two views of the period: that the principal form of scientific activity is experimentation and that 13th-century Europe still represented the "[[Dark Ages (historiography)|Dark Ages]]".{{sfn|Hackett (1997), "Scientia Experimentalis"|p=279}} This view, which is still reflected in some 21st-century [[popular science]] books,{{refn |E.g., [[Brian Clegg (writer)|Clegg]]'s 2003 treatment of Roger Bacon, entitled ''The First Scientist''.{{sfnp |Clegg |2003}}<ref>{{citation |last=Wooley |first=Benjamin |author-link=Benjamin Wooley |author-mask=Wooley |date=17 May 2003 |contribution-url=https://www.theguardian.com/books/2003/may/17/featuresreviews.guardianreview10 |contribution=Review of ''The First Scientist'' |title=The Guardian |url=http://www.guardian.co.uk }}</ref>{{sfnp |Goldstone & al. |2005}}}} portrays Bacon as an advocate of modern experimental science who emerged as a solitary genius in an age hostile to his ideas.{{sfnp|Gray|2011|p=184}} Based on Bacon's [[#Apocrypha|apocrypha]], he is also portrayed as a visionary who predicted the invention of the [[submarine#History|submarine]], [[history of aviation|aircraft]], and [[automobile#History|automobile]].{{sfnp|Mayer|1966|pp=500–501}} Consistent with this view of Bacon as a man ahead of his time, [[H. G. Wells]]'s ''[[The Outline of History|Outline of History]]'' attributes this prescient passage to him:<blockquote>Machines for navigating are possible without rowers, so that great ships suited to river or ocean, guided by one man, may be borne with greater speed than if they were full of men. Likewise, cars may be made so that without a draught animal they may be moved ''cum impetu inaestimabili'', as we deem the scythed chariots to have been from which antiquity fought. And flying machines are possible, so that a man may sit in the middle turning some device by which artificial wings may beat the air in the manner of a flying bird.<ref name=Wells>[https://archive.org/details/hgwellsoutlinehistoryvol2/page/638/mode/1up?view=theater Wells, H. G., ''The Outline of History'', Vol. 2, Ch. 33, §6, p. 638 (New York 1971) ("updated" by Raymond Postgate and G. P. Wells).]</ref></blockquote>

However, in the course of the 20th century, [[Edmund Husserl|Husserl]], [[Martin Heidegger|Heidegger]] and others emphasised the importance to the modern science of [[René Descartes|Cartesian]] and [[Galileo Galilei|Galilean]] projections of [[mathematics]] over sensory perceptions of nature; Heidegger, in particular, noted the lack of such an understanding in Bacon's works.{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}} Although [[Alistair Cameron Crombie|Crombie]],{{sfnp|Crombie|1953}} [[Thomas Kuhn|Kuhn]]{{sfnp|Kuhn|1976}} and {{ill|Matthias Schramm|de|Matthias Schramm (Wissenschaftshistoriker)|lt=Schramm}}{{sfnp|Schramm|1998}} continued to argue for Bacon's importance to the development of "qualitative" areas of modern science,{{sfnp|''Stanford Encyclopedia of Philosophy''|2013|loc=§1}} [[Pierre Duhem|Duhem]],{{sfnp|Duhem|1915|p=442}} [[Lynn Thorndike|Thorndike]],{{sfnp|Thorndike|1914}}{{sfnp|Thorndike|1916}} [[Raoul Carton|Carton]]{{sfn|Hackett (1997), "Scientia Experimentalis"|p=280}} and [[Alexandre Koyré|Koyré]]{{sfnp|Koyré|1957}} emphasised the essentially medieval nature of Bacon's ''{{lang|la|scientia experimentalis}}''.{{sfn|Hackett (1997), "Scientia Experimentalis"|p=280}}{{sfnp|Lindberg|1996|p=lv}}

Research also established that Bacon was probably not as isolated—and not as persecuted—as was once thought. Many medieval sources of and influences on Bacon's scientific activity have been identified.{{sfn|Hackett (1997), "Scientia Experimentalis"|pp=279–284}} In particular, Bacon often mentioned his debt to the work of [[Robert Grosseteste]]:{{sfn|Hackett (1997), "Life"|pp=11–12}} his work on [[#Optics|optics]] and the [[#Calendrical reform|calendar]] followed Grosseteste's lead,{{sfnp|Crombie|1990|p=129}} as did his idea that [[inductive reasoning|inductively-derived conclusions]] should be submitted for verification through experimental testing.{{sfnp|Gauch|2003|p=222}}

Bacon noted of [[William of Sherwood]] that "nobody was greater in philosophy than he";{{sfnp|Brewer|1859}}{{sfnp|Wood|1786|p=[https://archive.org/stream/historyantiquiti00wood#page/38/mode/2up 38]}} praised [[Petrus Peregrinus de Maricourt|Peter of Maricourt]] (the author of "A Letter on Magnetism")<ref>{{citation |last=Turner |first=Gillian |author-mask=Turner |title=North Pole, South Pole |date=2010 }}</ref> and [[John of London]] as "perfect" mathematicians; [[Campanus of Novara]] (the author of works on astronomy, astrology, and the calendar) and a Master Nicholas as "good";{{sfnp|Molland|1997}} and acknowledged the influence of [[Adam Marsh]] and lesser figures. Some scholars have pushed back on his reputation as an isolated genius.{{sfn|Hackett (1997), "Life"|pp=11–12}}

As a result, the picture of Bacon has changed. Bacon is now seen as part of his age: a leading figure in the beginnings of the [[medieval university|medieval universities]] at [[University of Paris#History|Paris]] and [[University of Oxford|Oxford]] but one joined in the development of the philosophy of science by [[Robert Grosseteste]], [[William of Auvergne]], [[Henry of Ghent]], [[Albertus Magnus|Albert Magnus]], [[Thomas Aquinas]], [[Duns Scotus|John Duns Scotus]], and [[William of Ockham]].{{sfnp|Gauch|2003|p=51}} [[David C. Lindberg|Lindberg]] summarised:
<blockquote>Bacon was not a modern, out of step with his age, or a harbinger of things to come, but a brilliant, combative, and somewhat eccentric [[scholasticism|schoolman]] of the thirteenth century, endeavoring to take advantage of the new learning just becoming available while remaining true to traditional notions{{nbsp}}... of the importance to be attached to philosophical knowledge".{{sfnp|Lindberg|1987|p=520}}</blockquote>

A recent review of the many visions of Bacon across the ages says contemporary scholarship still neglects one of the most important aspects of his life and thought: his commitment to the Franciscan order. 
<blockquote>His {{lang|la|Opus majus}} was a plea for reform addressed to the supreme [[Pope|spiritual head of the Christian faith]], written against a background of [[Apocalypse|apocalyptic]] expectation and informed by the driving concerns of the [[friar]]s. It was designed to improve training for [[missionary|missionaries]] and to provide new skills to be employed in the defence of the Christian world against the enmity of non-Christians and of the [[Antichrist]]. It cannot usefully be read solely in the context of the [[history of science]] and [[history of philosophy|philosophy]].{{sfnp|Power|2006}}</blockquote>

With regard to religion's influence on Bacon's philosophy, [[Charles Sanders Peirce]] noted, "To Roger Bacon,{{nbsp}}... the schoolmen's conception of reasoning appeared only an obstacle to truth{{nbsp}}... [but] Of all kinds of experience, the best, he thought, was interior illumination, which teaches many things about Nature which the external senses could never discover, such as the [[transubstantiation]] of bread."<ref>{{citation |last=Peirce |first=Charles Sanders |author-link=Charles Sanders Peirce |date=1877 |title=The Fixation of Belief |url=http://www.peirce.org/writings/p107.html }}</ref> Later scholars have therefore viewed him as a proto-protestant.<ref name="Porterfield 2006 p. 136">{{cite book | last=Porterfield | first=A. | title=The Protestant Experience in America | publisher=Greenwood Press | series=American religious experience | year=2006 | isbn=978-0-313-32801-5 | url=https://books.google.com/books?id=V9VM9NEsqXwC&pg=PA136 | access-date=2023-05-29 | page=136}}</ref>

In [[University of Oxford|Oxford]] lore, Bacon is credited as the namesake of [[Folly Bridge]] for having been placed under house arrest nearby.{{sfnp|Smith|2010|loc=[https://books.google.com/books?id=JAE7AwAAQBAJ&pg=PT21 "Bacon Friar"]}} Although this is probably untrue,<ref>{{citation |last=Thacker |first=Frederick Samuel |author-mask=Thacker |title=The Stripling Thames |url=http://thames.me.uk/0TST/t00020.htm |date=1909 |volume=Ch. 2 }}</ref> it had formerly been known as "Friar Bacon's Bridge".<ref>{{citation |author=C. |contribution=Friar Bacon's, or Folly Bridge, Oxford |date=Aug 1829 |page=105 |contribution-url=https://books.google.com/books?id=IvdfAAAAcAAJ&pg=PA105 |editor-last=Cave |editor-first=Edward |editor-link=Edward Cave |display-editors=0 |title=Gentleman's Magazine |url=https://books.google.com/books?id=IvdfAAAAcAAJ }}</ref> Bacon is also honoured at Oxford by a plaque affixed to the wall of the [[Westgate Oxford|Westgate shopping centre]].{{sfnp|Smith|2010|loc=[https://books.google.com/books?id=JAE7AwAAQBAJ&pg=PT21 "Bacon Friar"]}}

==In popular culture==
[[File:William Blake, Visionary Heads of Friar Roger Bacon and Poet Gray.jpg|upright|thumb|[[William Blake]]'s ''[[Visionary Heads|visionary head]]'' of "Friar Bacon"]]
To commemorate the 700th anniversary of Bacon's approximate year of birth, [[John Erskine (educator)|Prof. J. Erskine]] wrote the biographical play ''A Pageant of the Thirteenth Century'', which was performed and published by [[Columbia University]] in 1914.{{sfnp|Erskine|1914}}<ref>{{citation |last=Baker |first=Blanch M. |author-mask=Baker |title=Dramatic Bibliography |date=1933 |page=[https://books.google.com/books?id=4iL0a2rQzsgC&pg=PA180 180] }}</ref> A fictionalised account of Bacon's life and times also appears in the second book of [[James Blish]]'s ''After Such Knowledge'' trilogy, the 1964 ''[[Doctor Mirabilis (novel)|Doctor Mirabilis]]''.{{sfnp|Blish|1964}} Bacon serves as a mentor to the protagonists of [[Thomas B. Costain|Thomas Costain]]'s 1945 ''[[The Black Rose (novel)|The Black Rose]]'',<ref>{{cite web|title=Roger Bacon|url=https://sites.google.com/site/lis763theblackrose/for-history-buffs/roger-bacon|work=The Black Rose|publisher=Google Sites|access-date=27 April 2014}}</ref><ref>{{cite web|title=The Black Rose|url=http://unsworth.unet.brandeis.edu/courses/bestsellers/search.cgi?title=The+Black+Rose|publisher=Brandeis University|access-date=27 April 2014|archive-url=https://web.archive.org/web/20140428004449/http://unsworth.unet.brandeis.edu/courses/bestsellers/search.cgi?title=The+Black+Rose|archive-date=28 April 2014|df=dmy-all}}</ref> and [[Umberto Eco]]'s 1980 ''[[The Name of the Rose]]''.<ref>{{citation |last=Scult |first=A. |date=1985 |contribution=Book Reviews |title=The Quarterly Journal of Speech |volume=71, No.&nbsp;4 |issue=4 |pages=489–506 |doi=10.1080/00335638509383751 }}</ref>
[[Robert Greene (dramatist)|Greene]]'s [[Friar Bacon and Friar Bungay|play]] prompted a less successful sequel ''[[John of Bordeaux]]'' and was recast as a children's story for [[James Baldwin (editor and author)|James Baldwin]]'s 1905 ''Thirty More Famous Stories Retold''.{{sfnp|Baldwin|1905}} "The [[Brazen Head]] of Friar Bacon" also appears in [[Daniel Defoe]]'s 1722 ''[[A Journal of the Plague Year|Journal of the Plague Year]]'', [[Nathaniel Hawthorne]]'s 1843 "[[The Birth-Mark]]" and 1844 "[[The Artist of the Beautiful]]", William Douglas O'Connor's 1891 "The Brazen Android" (where Bacon devises it to terrify [[Henry III of England|King Henry]] into accepting [[Simon de Montfort, 6th Earl of Leicester|Simon de Montfort]]'s demands for greater democracy),<ref>{{citation |last=Anders |first=Charlie Jane |contribution-url=http://io9.com/5260116/walt-whitmans-best-friend-wrote-the-first-robot-revolution-story |contribution=Walt Whitman's Best Friend Wrote the First Robot Revolution Story |date=18 May 2009 |title=io9 |url=http://www.io9.com }}</ref><ref>[[William Douglas O'Connor|O'Conner]], "[https://archive.org/details/BrazenAndroid The Brazen Android]" (audiobook hosted at Internet Archive).</ref> [[John Cowper Powys]]'s 1956 ''The Brazen Head'', and [[Robertson Davies]]'s 1970 ''[[Fifth Business]]''.<ref>{{cite web|title=Fifth Business|url=http://www.studymode.com/essays/Fifth-Business-8315.html|publisher=Study Mode|access-date=27 April 2014}}</ref> Bacon appears in Rudyard Kipling's 1926 story 'The Eye of Allah'.

==See also==
* [[Baco (crater)|Baco]], a lunar crater named for Roger Bacon
* [[History of geomagnetism]], [[Translation#Western theory|of translation]], [[History of scientific method|of the scientific method]], and [[History of science|of science in the Middle Ages]]
* [[John of St Amand]]
*[[List of Catholic clergy scientists]]
* [[Oxford Franciscan school]]
* [[Roger Bacon High School]]
* [[Vitello]]
* [[Wilfrid Voynich]]

==Notes==
{{Reflist|group=n}}

== References ==
=== Citations ===
{{Reflist|25em}}

=== Sources ===
==== Primary sources ====
{{refbegin|30em}}
* {{citation |author=Anonymous |author-mask=Anon. |ref={{harvid |''Fryer Bacon'' |1627}} |title=The Famous Historie of Fryer Bacon: Containing the wonderfull things that he did in his Life: Also the manner of his Death; With the Lives and Deaths of the two Coniurers<!--sic-->, ''Bungye'' and ''Vandermast'' |location=London |publisher=G. Purslowe for F. Grove |year = 1627 |url = http://penelope.uchicago.edu/bacon/baconhistory.html }}.
* {{citation |last=Bacon |first=Roger |editor-last=Brewer |editor-first=J.S. |ref={{harvid |Brewer|1859}} |year = 1859 |title=Opera Quaedam Hactenus Inedita, ''Vol.&nbsp;I:'' Opus Tertium, Opus Minus, Compedium Philosophiae, & De Nullitate Magiae |location=London |series = ''[[Chronicles and Memorials of Great Britain and Ireland during the Middle Ages]]'', No.&nbsp;15 |url = http://gallica.bnf.fr/ark:/12148/bpt6k50167j/f7.image |publisher=Eyre & Spottiswoode for Longman, Green, Longman, & Roberts |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=The 'Opus Majus' of Roger Bacon |editor-last=Bridges |editor-first=John Henry |year = 1897 |location=Oxford |publisher=Horace Hart for the Clarendon Press |language = la, en }}
** [https://archive.org/stream/opusmajusofroger01baco volume I]
** [https://archive.org/stream/opusmajusofroger02baco volume II]
* {{citation |last=Bacon |first=Roger |title=The 'Opus Majus' of Roger Bacon: Edited, with Introduction and Analytical Table, ''Supplementary Volume:'' Containing—Revised Text of First Three Parts; Corrections; Emendations; and Additional Notes |url = https://archive.org/stream/b24975655_0003#page/n5/mode/2up |editor-last=Bridges |editor-first=John Henry |date=1900 |ref={{harvid |Bridges|1900}} |location=London |publisher=Williams & Norgate |language = la, en }}
* {{citation |last=Bacon |first=Roger |author-link=Roger Bacon |editor-last=Nolan |editor-first=Edmond |editor2-last=Hirsch |editor2-first=S.A. |display-editors=1 |title=Grammatica Graeca ''[''Greek Grammar'']'' |location=[[Cambridge, England|Cambridge]] |year = 1902 |ref={{harvid|Nolan & al.|1902}} |publisher=Cambridge University Press |language = la, el }}
* {{citation |last=Bacon |first=Roger |editor-last=Duhem |editor-first=Pierre |ref={{harvid|Duhem|1909}} |location=Quaracchi (Clara Aqua) |year=1909 |title=Un Fragment Inédit de l'Opus Tertium de Roger Bacon, Précédé d'une Étude sur Ce Fragment |url = http://capricorn.bc.edu/siepm/DOCUMENTS/BACON/Bacon_Fragment%20Op%20Tert.pdf |publisher=[[College of St Bonaventure]] (Collegium S. Bonaventurae) |language = la, fr }}
* {{citation |last=Bacon |first=Roger |title=Metaphysica: De Viciis Contractis in Studio Theologie |url = https://archive.org/details/operahactenusine01baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;I |location=Oxford |publisher=Henry Frowde for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |ref={{harvid|Steele|1909}} |year = 1909 |language = la, en }}<!-- undated -->
* {{citation |last=Bacon |first=Roger |title = Communium Naturalium, ''Vol.&nbsp;I, Pt.&nbsp;I&nbsp;& II'' |url = https://archive.org/details/operahactenusine02baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;II |location=Oxford |publisher=Henry Frowde for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |ref={{harvid|Steele|c. 1910}} |year = c. 1910 |language = la, en }}<!--undated-->
* {{citation |last=Bacon |first=Roger |title=Communium Naturalium, ''Vol.&nbsp;I, Pt.&nbsp;III&nbsp;& IV'' |url = https://archive.org/details/operahactenusine03baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;III |year = 1911 |location=Oxford |publisher=Henry Frowde for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |ref = {{harvid|Steele|1911}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |editor-last=Little |editor-first=Andrew George |ref={{harvid|Little|1912}} |year = 1912 |url = https://archive.org/details/partofopustertiu04baco |title=Part of the Opus Tertium of Roger Bacon, Including a Fragment Now Printed for the First Time |location=Aberdeen |series=''British Society of Franciscan Studies'', No.&nbsp;IV |publisher=Aberdeen University Press |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=Communium Naturalium, ''Vol.&nbsp;II:'' De Celestibus |url = https://archive.org/stream/operahactenusine04baco#page/n5/mode/2up |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;IV |date=1913 |location=Oxford |publisher=Henry Frowde for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |ref = {{harvid|Steele|1913}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=Secretum Secretorum cum Glossis et Notulis Tractatus Brevis et Utilis ad Declarandum Quedam Obscure Dicta |url = https://archive.org/stream/operahactenusine05baco#page/n5/mode/2up |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;V |date=1920 |location=Oxford |publisher=Humphrey Milford for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |editor2-last=Fulton |editor2-first=A.S. |display-editors=1 |ref = {{harvid |Steele & al.|1920}} |language = la, en }}
* {{citation |last3=Dei |first3=Alexander de Villa |last=Bacon |first=Roger |author2-last=Grosseteste |author2-first=Robert (Robertus Grossecaput) |display-authors=1 |title=Compotus |url=https://archive.org/details/p6p7operahactenu00baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;VI |year=1926 |location=Oxford |publisher=Humphrey Milford for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |ref = {{harvid|Steele|1926}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=Questiones Supra Undecimum Prime Philosophie Aristotelis (Metaphysica XII), ''Pt. I & II'' |url = https://archive.org/stream/p6p7operahactenu00baco#page/n337/mode/2up |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;VII |year = 1926 |location=Oxford |publisher=John Jonson for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |editor2-last=Delorme |editor2-first=Ferdinand M. |display-editors=1 |ref={{harvid|Steele & al.|1926}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |title = Questiones Supra Libros Quartuor Physicorum Aristotelis |url = https://archive.org/details/operahactenusinep8p9baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;VIII |year = 1928 |location=Oxford |publisher=Humphrey Milford for the Clarendon Press |editor2-last=Steele |editor2-first=Robert |editor2-link=Robert Steele (medievalist) |editor-last=Delorme |editor-first=Ferdinand M. |display-editors=1 |ref={{harvid|Delorme & al.|1928}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=De Retardatione Accidentium Senectutis cum Aliis Opusculis de Rebus Medicinalibus |url = https://archive.org/stream/operahactenusinep8p9baco#page/284/mode/2up |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;IX |year = 1928 |location=Oxford |publisher=Humphrey Milford for the Clarendon Press |editor2-last=Withington |editor2-first=E. |editor-last=Little |editor-first=Andrew George |display-editors=1 |ref={{harvid |Little & al.|1928}} |language = la, en }}
* {{citation |last=Bacon |first=Roger |title=Questiones supra Libros Prime Philosophie Aristotelis (Metaphysica I, II, V–X) |url = https://archive.org/details/operahactenusine10baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;X |date=1930 |location=Oxford |publisher=John Jonson for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |editor2-last=Delorme |editor2-first=Ferdinand M. |display-editors=1 |ref = {{harvid |Steele & al. |1930}} |language = la, en }}
* {{citation |author2=Aristotle |last=Bacon |first=Roger |display-authors=1 |title=Questiones Altere supra Libros Prime Philosophie Aristotelis (Metaphysica I–IV), Questiones supra de Plantis, & Metaphysica Vetus |url = https://archive.org/details/operahactenusine11baco |series=''Opera Hactenus Inedita Rogeri Baconi'', No.&nbsp;XI |year = 1932 |location=Oxford |publisher=John Jonson for the Clarendon Press |editor-last=Steele |editor-first=Robert |editor-link=Robert Steele (medievalist) |editor2-last=Delorme |editor2-first=Ferdinand M. |display-editors=1 |ref={{harvid|Steele & al.|1932}} |language = la, en |author2-link=Aristotle }}
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{{refend}}

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* {{citation |last=Williams |first=Steven J. |contribution=Roger Bacon and the ''Secret of Secrets'' |pages=365–374 |editor-last=Hackett |editor-first=Jeremiah M.G. |display-editors=0 |title=Roger Bacon and the Sciences: Commemorative Essays |series=''Studien und Texte zur Geistesgeschichte des Mittelalters'', No.&nbsp;57 |url = https://books.google.com/books?id=Gy3Vp7TurVUC |location=Leiden |publisher=Brill |year=1997 |isbn=90-04-10015-6 }}.
* {{citation |last=Wood |first=Antony |url=https://archive.org/stream/historyantiquiti00wood#page/n5/mode/2up |title=The History and Antiquities of the Colleges and Halls in the University of Oxford |editor-last=Gutch |editor-first=John |author-link=Anthony Wood (antiquary) |editor-link=John Gutch |display-editors=0 |location=Oxford |publisher=Clarendon Press |year=1786 }}.
* {{citation |last=Wood |first=Anthony à |author-link=Anthony Wood (antiquary) |title=The History and Antiquities of the University of Oxford, ''Vol.&nbsp;II'' |url = https://books.google.com/books?id=0gYVAAAAQAAJ |editor-last=Gutch |editor-first=John |editor-link=John Gutch |display-editors=0 |location=Oxford |year=1796 }}.
* {{citation |last=Zambelli |first=Paola |title=White Magic, Black Magic in the European Renaissance |year=2007 |location=Leiden |publisher=Brill |isbn=978-90-04-16098-9 }}.
{{refend}}

==External links==
{{commons category}}
{{wikiquote}}
{{wikisource|works=or}}
* {{cite SEP |url-id=roger-bacon |title=Roger Bacon |last=Hackett |first=Jeremiah}}
* [https://www.bbc.co.uk/programmes/b08m8z2w "Roger Bacon" – In Our Time 2017]
* {{cite IEP |url-id=bacon-ro |title=Roger Bacon}}
* {{cite IEP |url-id=bacon-la |title=Roger Bacon on Language}}
* {{Cite CE1913|wstitle=Roger Bacon |mode=cs2}}
* [http://www.jewishencyclopedia.com/view.jsp?artid=79&letter=B 1901–1906 Jewish Encyclopedia: Bacon, Roger]
* [https://web.archive.org/web/20070714015552/http://mathdl.maa.org/convergence/1/?pa=quote&sa=browseQuotesFrontEnd&sortLetter=b Roger Bacon Quotes] at [http://mathdl.maa.org/convergence/1/ Convergence]
* [http://www.fordham.edu/halsall/source/bacon2.html Roger Bacon: On Experimental Science, 1268]
* {{MacTutor Biography|id=Bacon}}
* [http://www.levity.com/alchemy/rbacon.html Brehm, Edmund A., "Roger Bacon's Place in the History of Alchemy"]
* {{cite encyclopedia |url=http://www.britannica.com/biography/Roger-Bacon |title=Roger-Bacon |encyclopedia=Britannica Encyclopedia|date=January 2024 }}
* [https://i.pinimg.com/736x/e2/ba/0e/e2ba0e78be05d6431464050bb5609867--medieval-philosophy-roger-bacon.jpg classic wood engraving of Roger Bacon's visage, appears in Munson and Taylor's "Jane's History of Aviation" c.1972]
* {{Librivox author |id=12734}}

{{Medieval Philosophy|state=expanded}}
{{philosophy of science}}
{{History of Catholic theology}}
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{{Alchemy}}

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