Prior to the examination of the Islamic impact on some specific sciences such as astronomy, mathematics, optics, etc, it is first necessary to look at how the Islamic influence revolutionised learning. How Islamic science  was taken up by a second generation of influential Western scholars, knowledge which they Latinised and legitimised for their milieus, and which allowed the first Western institutions of higher learning to emerge. Islam also provided modern science with observation, measurement, the search for accuracy, scientific methodology, etc, all seized upon by Western Christendom. 

Early Men of Learning of The Christian West

  The first wave of Western Christian scholars has already been dealt with at great length. This included the likes of Adelard of Bath , Gerbert , Petrus Alphonsi , Walcher of Malvern, Daniel of Morley, Constantine the African  etc… all scholars, and for most, translators, too. Their crucial role in the awakening of Western Christendom  has been considered, the English, amongst them, as a group, for instance, as Haskins  notes, put England  at the centre in the diffusion of Islamic science s throughout Western Europe in the 12^th century, mainly thanks to Adelard,[1] whose works, and pioneering trust for Islamic learning, mark a significant stage in the history of ideas.[2] The labours of these early men led to a wide variety of scientific advances in the 13^th century.[3] Advances furthered by scholars on whom emphasis is placed in the following.

The list includes the likes of Roger Bacon  (1220-1294), Robert Grosseteste  (1175-1253), Albertus Magnus (1206-1280), Thomas Aquinas  (d.1274), Arnold of Villanova (d.1311) etc. They were the first to adapt Islamic learning on Western ground, Latinise such learning, not just in form (as those before them did), but also in the manner it is diffused, besides, of course, building upon it. All these second wave scholars appeared to the fore in the 13^th century, in the wake of the translations just discussed, and all of them, were connected in one way or another with institutions or regions where Islamic learning was dominant: Southern Italy, Spain, Montpellier , etc. All knew Arabic; and evidently, all their works bear, some up to the totality, Islamic influences. These characteristics are looked at here through the lives and works of Aquinas, Bacon and Grosseteste.

 Before these three are dealt with, it is appropriate to skip briefly through some other names and their works, as diversely as possible, to highlight the Islamic influence on them.

  Beginning with optics and John Peckham (fl. Second half of 13^th)  (theologian, mathematician, and physicist), a Franciscan, who spent his life in Paris, Oxford, Rome and as Archbishop of Canterbury from 1279 to his death. His optics is largely derived from Ibn al-Haytham, where he also refers to the camera obscura, just as to be found in the works of Bacon  and Witelo .[4]

The Polish philosopher and physicist Witelo  (Vitelo) (1230-1275) was a Dominican born in Silesia, whose optics is largely derived from the work of Ibn al-Haytham. The value of his work is much impaired if one realises how much of it was of such provenance, Sarton  observes, but his followers did not realise this and admired him far beyond it should have been the case.[5]Witelo’s work did lack explicit acknowledgement of the source, though.[6] In his lengthy introduction to Optica Thesaurus, Lindberg highlights Witelo's close reliance on Ibn al-Haytham.[7] The best demonstration for such resemblance, Lindberg points out, being `simply to follow the cross-references between Al-Hazen (Ibn al-Haytham) and Witelo in the Pisner edition of their works: one quickly learns that for the most part Witelo treats the same topics in the same fashion, and sometimes in even the same words. Occasionally Witelo omits a topic, and sometimes he seeks to clarify Alhazen's points by further elaboration on a tightening of the argument, but seldom does he depart from his principal source.’[8]

Witelo ’s optical treatise Perspective, Birkenmajer says, is well ordered and full of good facts, and its scientific worth is not compromised by the fact that the author derived the largest part of his knowledge from the Aspectibus of Ibn al-Haytham.[9]  Even when he sought to explain the problem of optical illusion in his Denatura demonum, Witelo also relied on Ibn al-Haytham.[10]  Ibn al-Haytham deeply impacted on Witelo on other matters, which include the study of Ibn al-Haytham’s optical treatises at Padua, in Italy, in seeking to explain optical phenomena met in the grottos of Covolo, and also, in his Scientia motuum coelestium, where he, Witelo, deals with the proportion of distance between the earth and the sphere of fixed stars.[11] Witelo’s work on visual illusions, which he derived from Ibn al-Haytham had an impact on Nicolas Oresme via his commentary on the Meteore.[12]

Theodoric of Freiberg, just like Witelo , leaned, and considerably, on Ibn al-Haytham (referred to as `auctor perspectiva') and to a lesser extent on Ibn Rushd  (`Commentator'), Ibn Sina  and Al-Farabi.[13] His theory of colour was somewhat more novel, following Ibn al-Haytham, and in contrast to Bacon , he treated colour as real as light itself.[14]

  Leopold of Austria was an astronomer and meteorologist, who flourished probably in the middle of the second half of the 13^th century. He composed an astronomical compilation, appropriately entitled Compilatio de astronum scientia, divided into ten treatises. The author was acquainted with the tables of al-Zarqali, and a very large part of his work was derived from the Kitab al-madkhal (The Introduction) of Abu Ma'ashar.[15] A French translation of Leopold's Compilatio (li compilacions Leupo le fil le duc d'Austeriche de le science des estoiles) came to be owned by Mary of Luxembourg, queen of France (d. 1324).[16]

 The astronomical work by John of Holywood  (d. 1250) who was long a teacher at Paris, was universally popular, existing in numerous manuscripts, and was translated into most European vernaculars.[17] It contains, however, no new or original elements and is put together from translations of Muslim works.[18] The Tractatus de Sphaera, or Sphaera Mundi, completed in 1233 by Sacrobosco (John of Holywood) is, indeed, nearly a word by word reproduction of al-Farghani and al-Battani.[19] 

 Vincent of Beauvais’s Speculum naturale’s astronomy is a reproduction of al-Bitruji's theory (on the sphere) as distorted by Albert (Magnus).[20]

Chaucer's (1340-1400) treatise on the astrolabe written in 1390, appears to be a re-statement of an Islamic work of the 8^th-9^th Century.[21] Chaucer’s use of the `contemporary sciences’ in presenting the physical and spiritual condition of man, medieval and universal, reflects the observations, ideas, and methodology of great `Arabian’ masters who occur throughout the body of his works, as he names them: Alkabucious, Alocen, Arsechiel, Averrois, Avycen, Haly, Razis.[22] Chaucer equally refers to Constantyn (the African) and Piers Alfonce (Petrus Alfonsi), the pioneer of Islamic studies on English soil.[23]

John of Genoa , another astronomer (fl 1332-37), compiled tables for the computation of eclipses in 1332 derived partly from al-Battani;[24] whilst Ristoro d'Arezzo (fl c.1282) completed in Arezzo (Tuscany) an encyclopaedic treatise on the composition of the world, in Italian: Della composizione del mondo colle sue cagioni, which deals with astronomy, meteorology, and geology, largely derived from Latin  translations of Islamic works of the 9^th century by al-Farghani, Sahl ibn Bishr, Abu Ma'ashar; and he may also have used Ibn Sina ' Qanun, and Ibn Rushd 's commentary on Aristotelian meteorology.[25]

The geological ideas of the great encyclopaedists, Vincent of Beauvais and Albert the Great, were essentially derived from Muslim sources, including The Kitab al-Shifa of Ibn Sina , the so called Avicennae Mineralia translated by Alfred of Sareshel. When they explain the movements of the sea, erosion, the generation of mountains, they are simply repeating the words of Ibn Sina or of the unknown author of the De elementis.[26] Vincent of Beauvais’s geological part of Speculum naturale is derived from Ibn Sina through Albert the Great.[27]

Al-Biruni ’s Tahdid nihayat al-amakin (The identification of the end of places), written in 1025, speaks of the alternations of dry land and sea, and in another text he remarks that the Indus valley should be considered an ancient sea basin filled with alluvium.[28] Similar views appeared in Albert the Great (Albertus Magnus) and Ristoro d'Arezzo (13^th century); the latter even referred to fossil fishes, and so did Joinville in his life of St. Louis.[29]

  Lanfrank, who was both practioner in Paris, and also a teacher is the author of the Chirurgia magna, where he insists on the study of good clinical cases, and where he sets down the foundations of French surgery. Lanfrank relies, and vastly, on Islamic sources, which include Hunain Ibn Ishaq, Al-Razi , Ishaq al-Israeli, Ali Ibn Abbas, Abu-l-Qasim, Ibn Sina , Constantine, Ibn Sarabi, Ibn Rushd,  etc.[30]

Equally, Arnold of Villanova’s sources of influence were mainly Muslim Spain, Valencia , most particularly, and Montpellier .[31]His translations and other aspects of his scholarly life have already been covered, just to add here observations made by Daniel, that Arnold copied so much Al-Razi , that he (Daniel) sees in him a sort of lesser and European Al-Razi.[32] Arnold covers so large a field, Daniel observes, that he must be thought a re-editor as much as an author;[33] plagiarism, Daniel notes, is meaningless in the mediaeval context, `but almost the whole of the medical culture of Europe with all its acquisitions from the Arabs  seems to pass through his pen.’[34]

 John of St Amand (d. early 14^th) was a Belgian physician (working in Paris,) and canon (of Tournai, Belgium.) His fame is based upon two works: a commentary on the antidotary of Nicholas of Salerno  Expositio sive additio super antidotarium Nicolai, and a medical compendium called Revocativum memoriae.[35] The first work deals, exactly in the Salernitan tradition as introduced by Constantine, with digestion, evacuation (spontaneous, or artificial by means of purgation, bloodletting, leeches, etc.), up-building, bloodletting, uroscopy, diet etc. For both works, his main sources include Al-Razi , Hunain Ibn Ishaq, Ishaq al-Israeli, Ali Ibn Abbas, Ibn Sina , and, obviously, Constantine the African .[36]

   The Regimen du corps was written by Aldobrandin of Siena in 1256 for Beatrice of Savoy on the occasion of a journey which she undertook to visit her four daughters, the Queen of France, the Queen of England , the Queen of Germany, and the countess of Anjou (later Queen of Sicily ).[37] Such is the stature of Aldobrandin, that Countess Beatrice recommended him as a doctor to the French king Saint Louis himself.[38] The Regimen du corps is divided into four main parts dealing respectively with general and special hygiene of various organs (hair, eyes, ears, teeth and gums, face, stomach, liver, heart); dietetics and physiognomy.[39]This work is a near total reproduction of Muslim medical learning; its first two parts wholly based on Ibn Sina , and also on Ali Abbas and Hunayn Ibn Ishaq.[40] The third part follows Ishaq al-Israili, whilst the fourth and final part is a near literal translation of a part of the Kitab al-Mansuri of Al-Razi .[41]

Medical books often included a study of the weights and measures used by doctors. The best example of this class is the De Ponderibus e mensuris of Dino del Garbo (d.1327), which is more elaborate than other studies appearing in medical treatises, and is valuable for comparative purposes, for it includes Greek , Hebrew, and Arabic terms as well as Latin  ones; but Dino's main authority was the Qanun of Ibn Sina .[42]

And finally, here, mention must be made of John of Gaddesden (C.1280-1361),  a fellow of Merton College, Oxford, who compiled the famous treatise Rosa Anglica, which is mainly based on the works of both `Arabists’ Bernard de Gordon and Henry de Mondeville.[43]

  Very brief mention must be made of Albert the Great (1206-1280), who re-occurs quite often in this work, to note that his philosophical ideas are mainly derived from Al-Farabi, Ibn Sina , Al-Ghazali; Ibn Baja; and Ibn Rushd .[44] Hammond has shown that al-Farabi’s influence on Albertus Magnus (as on his pupil Aquinas ) is clearly visible in ontology, cosmology, psychology and theology.[45] In his comments on Aristotle , he chiefly uses Ibn Sina;[46] In anatomy and medicine, Albert must have used the Anatomia vivorum, or the translation of Ibn Sina's Qanun by Gerard of Cremona .[47] In meteorology and climatology, his views are mainly a clear summary of those transmitted by the Muslims. In geology and mineralogy, it was Ibn Sina's De Congelatione et conglutionatione lapidum; Ibn Sina’s influence also present in Albert’s Zoology.[48]

    The first of the three 13^th century main figures who is dealt with here is Robert Grosthead or (Greathead) Robert of Lincoln, better known as Robert Grosseteste  (1175-1253). He was born of humble parentage at Stradbrook, Suffolk, and was educated in Oxford and Paris(?). He was first chancellor of the University of Oxford; first lecturer to the Oxford Franciscans, 1224; Bishop of Lincoln from 1235 to his death in 1253. His scientific works are indebted to the texts brought to England  in the earlier stages of Islamic influence, records speaking of him as a master at Hereford , where Burnett  reminds us, Muslim mathematics and sciences flourished.[49] Grosseteste is also one of the earliest English authors to be acquainted with the writings of the Salernitan school.[50] It was, indeed, he who introduced that Salernitan medicine, with all its Islamic garb in England,[51]which later on a number of his students disseminated in turn. Just as his other sciences were also of Islamic origin to great measure.  Grosseteste astronomical ideas were partly derived from Al-Bitruji  after the latter was translated by Michael Scot.[52] His basing natural philosophy upon mathematics and experiment was extremely far reaching, although in this respect he was by no means the inventor of the experimental method, Muslims having preceded him by centuries (as seen in part one). A thorough study will indeed show from which source Grosseteste derived his ideas on experimentation, but it could well be Ibn al-Haytham. This was very much obvious in other areas as Grosseteste knew of the properties of convex lenses from a Latin  version of Ibn al-Haytham.[53] And Grosseteste developed from them a theory of the formation of the rainbow.[54]In this way he was clearly the forerunner of his most famous pupil, Roger Bacon , and he may have influenced the whole of Western Christendom , partly through his own writings, and partly through these new tendencies emphasised by Bacon and others.[55]

  Roger Bacon  (1220-1294) who lectured in both Paris and Oxford used Muslim philosophers in order to make polemic points against Islam, but seems genuinely to have liked what he quoted.[56] He argued that `our apprehension of the future life is like that of a deaf man's of music,’ and supported this from Ibn Sina .[57]Bacon was fond of this passage: `A man shall not be freed of this world and of its deceptions until, wholly taken up with that other heavenly world... the love of the things there draws him altogether away from thinking of anything lower.'[58] In his medical work Epistola de accidentibus senectutis Bacon also drew heavily from Islamic sources, that include the writings of Ibn Sina, Al-Razi , and Isaac Judaeus.[59] In mathematics his inspiration was al-Farabi, in astronomy it was Ibn al-Haytham and al-Kharaqi, and the former also influenced him with respect to optics, as also did al-Kindi.[60] In turn, Bacon influenced John Pecham and William st Cloud. He was in fact the first Latin  to make exposition of Ibn al-Haytham’s account of the eye, with its lens, as an optical system; following Ibn al-Haytham closely in accounting for the structure and function affecting vision.[61] Using the works Ibn al-Haytham (and al-Kindi’s) on lenses, he gave a geometrical description of the rainbow's position in the sky understanding it to be composed of a multiple of droplets.[62] Bacon’s commentary on the Secretum secretorum (a book of miscellaneous precepts for the guidance of human affairs, which was many times translated from Arabic during the Middle Ages, altered, augmented and edited by Bacon) shows good material on astronomy, on the size and sphericity of the earth, and on the relative extent of land and Sea.[63]

  Bacon  did step out of the Church boundaries in his too close borrowings from Islamic sources. After Stephen Tempier's condemnation of Ibn Rushd ’s theories in 1277, the Franciscan censorship struck harder, and in the following year Bacon was condemned for teaching `suspected novelties'. According to a Franciscan chronicle (Chronica viginti quattuor generalium, to 1374)  he was imprisoned from 1278 to 1292.[64]In his third letter to Pope Clement, Bacon held: `It is on account of the ignorance of those with whom I have had to deal that I have not been able to accomplish more.'[65]

Still, his legacy was considerable. He was an important link in the chain of scientific development, an authority at Oxford for centuries, an influence traceable through Pierre d'Ailly and the Imago Mundi to Columbus and through Paul of Middleburg (1445-1534), and the reform of the Gregorian calendar to Copernicus .[66] It was also he, Bacon , who first insisted that Latin  science of the Middle Ages came for the best part from other civilisations, and that it was useful to have a direct knowledge of original texts upon which was based that science.[67] He never wearied of declaring that `knowledge of Arabic and Arabian science was for his contemporaries the only way to true knowledge.'[68] Forster, it is, who, said, Bacon `drank deeply of the Arabian learning at the fountain head’ and provided `the undoubted origin of the rue astronomy as afterwards unfolded in the Copernican system’.[69]

  Born to a noble family near Naples, Thomas (Aquinas ) (c.1225-1274) was educated as a boy at the famous abbey of Monte Cassino. Later he studied at the newly established University of Naples (both institutions bed-sits of Islamic learning). Naples University, it must be remembered was founded by Frederick II , and this goes far, according to O’Leary `to account for his more accurate appreciation of Islamic teaching.’[70] After becoming a Dominican friar, Aquinas set out for Paris to study theology.[71] In the wide area that lies on the margins of theology and philosophy, he relied heavily on Muslim sources, mostly Ibn Sina , al-Ghazali and Ibn Rushd .[72]Aquinas appreciated Ibn Rushd most particularly, as `the supreme master in logic, but heretical in his metaphysics and psychology.’[73] Indeed, all kinds of subversive elements conglomerated around the views of Ibn Rushd as distorted by their `bigoted’ adversaries.[74] Supporters of Ibn Rushd were accused of questioning the fundamental doctrines of the Church, especially of doubting the dogmas of creation and of the immortality of the soul, of being materialists, etc.. They also had the bad reputation of being scientifically minded and prone to dialectics.[75] The enlargement of horizons by the Crusades , the increasing acquaintance with Islamic life and thought in East and West-all these, Durant holds, `could have produced an Aquinas even if Aristotle  had remained unknown; indeed the industry of Aquinas was due not to love of Aristole but to fear of Averroes (Ibn Rushd).’[76]Thus, while St Thomas was fighting for Christian rationalism and using many of the weapons forged by Ibn Sina, Al-Ghazzali, and Ibn Rushd, he was also fighting the subversive Ibn Rushd.[77] The aim of St Thomas, in this seeking to reproduce the arguments, formulas, and methods of Ibn Sina and his predecessors, was in seeking to reconcile reason and religion.[78] He was particularly prone to adopt the thoughts of Al-Farabi, Ibn Sina, Al-Ghazali, Ibn Baja, and, of course, Ibn Rushd, just as his teacher, Albertus Magnus was.[79]The particular impact of Al-Farabi (c.870-950) on Aquinas (just as on his teacher) is obvious in matters of cosmology, psychology and theology.[80]In the discussion of topics that were of great importance to his natural theology like the principle of causality and the `cosmological proofs’ of God, Aquinas merely repeats al-Farabi’s proofs.[81] Gilson also finds Ibn Sina’s influence on Aquinas in this particular area.[82]

  Aquinas , Durant points out, was always seeking his ways through, for the introduction of Islamic thoughts, but it must be reminded, this was the time of the Crusades  after all, and by his time, they were already nearly two century old of incessant warfare.[83]Where St Thomas accomplishes his great achievement is in his adopting the medium line as far as the situation in the Christian West  was concerned. He fought both Muslim rationalism and Christian irrationalism, following a line between the `Averroists’ of the left and the Scotists and Augustinians of the right, a conciliatory attitude, which made his prestige;[84] and which became the route for subsequent followers, opening the road to query whilst remaining within Church guidelines.