Opus majus

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into Latin ; as Jourda in thini si by Gerard of Cremona, the

translator os Ptolemy's Alma PSI. Allia Zen was the writer Onwhom Roger Bacon principalty relied ; though he mal es frequent use of the optical treatis es of Euclid, Ptolemy, Tideus and Alliindi.

The fit si begins with a bries exposition of the nature of lightand colour, and procee is to e XPla in the anatomy of the organs of vision. The second deals with the function of Vision and

with the physiology os perception. The third, with imperfections and illusiones incident to vision. The fourth, fifth and si Xth are devoted to the subject os reflexion. Seven k in is of mirrorS RI O di SCUSSed, plane, Spherical, cylindrica l. and conicat :the conveX and concave formS of the three laSt be ing Separate lyconsiderecl. The multiplication and position of the images formed is trea ted with in ordinate length, but with such geometrical si ill as to secure sor him an abidi nil place in thelii Story os pure, no less than os applied mathematics. His investigation,' says Cantor hichtes der Mathes=uati , vol i. p. 677 , ' of the problem In a Spherical concaUe mirror. to findthe poliat frona whicli an object os gi ven position ririli bereflected to an Cye of gi Uen position. is one Whicli, analyti Callyhand led, leacis to an equation of the foui th degree.' Allia ensolve d it, as Govi remari S Ptol. Ost. P. Ni X), by the use of an hyperbola. The seventh book of the hoonrnS Opticaes deals with refraction. A very elaborate description is gi ven of the instrument for mensuring it, part of whicli Bacon quoteS. More Uer, An attem set is made to e X pla in the cause of refraction whicli is substantialty identicat with Bacon 's. as may be seon hy com parison of Allia gen Vii. 8 with De Mult. Spesciarum, Pari II. CAP. 3. The apparatus for measuring the angle of refraction, which was more accurate ly designed than that os Ptolemy,

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INTRODUCTION.

enabled a series os observations to be made os the angle os refraction, in different media, on whicli the true laru of the Variations os refraction at different an gles and in different media might ultimate ly be base l. Vitello λ, Bacon 's contem Porary dre VP a table os refractions, as Ptolemy had donebe ore hi m. for the three media os air, water, and glasS. It waS soon Seen that the angle os res raction did not vary in accordance with the angle of inciden ce. But more than three CenturieS were to pasS bes ore the discovery of the law os sines, that is to Say, the law that the ratio os the sines of the an gles of incideiace and refraction is Constant sorrefraction in the fame medium, was effected by Sneli and

It might se em, at first si h t. that the optical work of Bacon was litile more than an ab ridgement of that os Allia gen η. Butthis vlew would render Bacon but scanty justice. Problem Sof great importa iace were indicated by hirn which Athagen hadenti rely neglected. In considering the poliat on the axis ofa Rpherical con Cave mirror to whi Ch rays were reflected, Bacon rem artis that this poliat would be different sor rays reflecte frona ea ch concoratri C circle traced round the Centre of them irror. Such a mirror Hiled there re to produce Complete

' Os Vitello, or Witelo. very litile is known. He describes himscis in his dedication to william os Morbeta identi fled by Cantor as William os Moerbeke as filius Thuringorum et Polonorum. In lib. X. 74 of hi S work hespealis of Poland as his count , and other passageS X. 42 and 62) Showthat he travelled in Italy. His work on Optics was editod with great care, and with many emendations, by Risner, and published at Hale in I 57ia in the

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must be other than spherical, it must be that produced by the

rotation os a coni C Section.

BACon, moreo Ver, is distinguished Dorn the Arabian optical writers, and from other in Vestigators of his o vn time; by his Sedulo his endeaVOurs to turn the diSco Uery os the laws of refleXion and refraction to practical account. Nei ther in Allia gentior in Vitello is there any attempt to constru Ct in StrumentS for the purpOSe of increa sing the power of Vision. With Bacon this object was always held steadi ly in View. of the simplemicroscope he had a persectly clear conception. His scientifici magination played freely with the possibilities of bring ingdistant objects 1 ear, and of indefinitely magnis ing minute objecis by giving Sui table directions to refracted rays, and by

the use of appropria te media. It would be, howeUer, an entire CX aggeration os his achi evemenis to spea k of him a s the inventor of the telescope. No eviden ce is sortii coming for his having effected the simple combination of twO ConVCX lonSOS, or os a ConveX with a concave lens, On whicli the power os

telescopi C Vision depencis. Ali that can tie clat med sor hirnis that he was the fit si definite ly and explicit ly to bring the

problem forward leaVing it for aster generationes to solve. In truth, his conception Os an optical image . as Constructed by the assem blage of foci of rays proceecling frona cach potnt of the object magnified. though in the main correct , wRS not at ab Sclearly grasped. Os the distinction belween virtual and reali mages, hi S notion was entii ely in de fauit. Νor, again, had Bacon a Clear conception os the Conditions os distinct vision. He e Xamine d to much bet ter pur pose than Allia gen had done the structu res of the eye : and he wRS a Arctos the refraction produced by the curveci sui face of the Cornea, and by the doub ly conveX crystalline lens. But what hes allecl to grasse ' was the necessi ty of a Clear image of the object efined on the retina; that image being prodii Ced by thes OCVSSing on the retina os rays procee ling from each potnt of the objeci. The Phenomena os accommodation, prodii Ced by the action of the ciliary muscle, whicli, by altering the CurUa-

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he had not anticipaled the physiological knowledge of the

of Jordanus Nemorarius, De Pon cribris, to whi Ch res ronce ismad C, UOl. i. P. I 60, had perhaps suggested the treaiment of the Phenomena of gravi ty as a distinct branch of science. No treati se by Lacon upon this subjeci, So far RS I am aware is e X tant ; and the se in re mari s in the fourth section os the

Speculations On the theory of gravitation. Nor is a nything known to tis of the way in whicli Bacontrea ted, is indoed he e ver attempted the science whicli hecalled Agricultura.' which, as we have Seen, was intended toinclude the stud y of li Ving hodies, Vegetable and animal. But the case is other vise with the science regat ded by him

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as weli as decetUed, and that others were impelled by wildhOpes of gain, has the pursuit os physical science in modern times been wholly free Dona similar tainis Θ Electrici tyapplied to medicine has been a sertile held sor impostors. And will any one maintain that the pursuit os chemistry has not been stimulated by hopes of industriat profit Z Yet stich

a Lavolsier, a Dalton, or a Faraclay. Alchemy was chemi Stryin iis prescienti sic period. Under the quid ance of hypotheseSwhich were not nearly SO wild or crude as they at firSt appear it attacked, like the true science whi Ch gradually grew fromit, the important problem os the transmutation os matter tib artificiat agen cies. It took for granted that metals were compound bodies, the elements of whicli might be separatecl

Sion S- Speculati Ue and operative. Under the latior was

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J XX vi INTRODUCTION. the transmutation os meta is, the discovery of the philosopher Segg, Or the Cli Xir vitae. Η ut Bacon was one of the se in whosaw that the empirical proceed ings of the honest mystics Ors Cheming Chariatans, who were tot ling at their royal road towealth Or longeUity, Covered speculations os a far deeper kind ;the stud y of the transition os matter frona the Mur Aristotelian elemenis, through in creasing degrees of compleXity UPto the hight y Compotand fornas eXhibited by organi ged hodieS. The Alkimia Speculativa ' os Bacon was, incleed, not alche myat ali as Common ly understOod: it was nothing less thanchemistry. 8 Al kimia Speculativa ' he says, in the twelisthchapter of the Optis Tesritam. treats of the generation of thingsi rom their elements and os ali in anima te things-as of the elements and liquids humores) simple and compotand common SionCS, RCIUS, RIad marbleS; go id, and other metal S; Sulphur, SaltS, pigmentS, lapis laguli, minium, and Other ColourS; OilS, bitumen, and Uery many other things of which we find nothingin the books of Aristolle; nor are the natural philosopherS Orany of the Latins ac quainted with these things. Aiad belligignorant of them. they Can know nothing of what follows inphySics, that is, of the generation os animate things-as

Ueget ableS, animal S, and man because knowing not what is prior, they muSt rema in ignorant os what is posterior. Forthe generation os men, and os brutes, and os planis, is stomelemental and liquid substances, and is of like manner with thegeneration of inanimate things. Where re, through ignorance of this science, ne i ther can natural PhiloSOPhy, Common ly SO- Called, be known, nor the theory, and theres ore ne i ther thepractice, of medicine ; not mere ly because natural philosophyand theoretical medicine are necessary for the practice, b Uthecause ali simple medicines are derived froni in animatelliings by this Science.'Os such fundamental trullis os chemicat science as thecomposition os air and water, the theory of combu Stion, and the chemistry Os carbon-he like his contemporariCS, wa Signorant; but the ignorance was Ahared by the second Bacon with the first, and was not to be dissipated for fi Ue Centuries. Ali that could be done in the mean while was to collect empi-

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rical insormation as to a seiu meta is and their oXides, sonae of the principat ali alis, acidS and salis. On ali these things the Arati investigators, Dona Geber clownwariis, had accumulate da considerable mass os materiai. It is not easy to define the resulis of each inquirer, o ing to the prevalent habit os describing their procedure and resulis in mysticat language. Selisede nce against Charges os magic and impos ture was probably their motive. And that the clanger was reat, the history of Bacon 's life sui aces to Sho . His efforis to refute the Charge of magi C were incessant. In his treatise, De Secretis operibus Artis et Inrae et de nul tau Maxiaes, he describes in delati the various procedures of the magician, si eight Ofhand , Ventri loquis m, pretended moUemenis os inani matethings in clim light the a id os accompli COS. ut teran CC of mySterious formulae, invocation of Spiriis. We gather frona thedescription that the lapse os si X centuries has done litile tochange the character of Charlatani Sm. But Bacon wRS aware that the chartatan was osten in POSSCSSion os Ualuatile SecretR

Many books a re held to be magicat, ' he says, hicli are notreatly so, but whicli contain important trullis o whicli are of this Lind, and whicli are not, it is for the eXperience of the wise man to decide. Is he find in them any result of naturalor artificiat forces opus naturae vel arti S), let him accept this: otherwise let hirti reject them as worthless.' Bacon Caresut lyguards himsels against dental os the mystical force of wordes ut tered under solemn conditioris, as in the dat ly miracle of the Eucharist, or in the Solemn invocations that protected the innocent when ex posed to judiciat ordeat. Such powersmight be exerted sor good as for evil ; and the unlawsul use of them was strict ly and Severely t O be condemnecl. Eut to whateVer eXtent Bacon may have sit area the illusionsos his time with regard to the practi Cal operationS os alchem y, it is a strii ing proos of his scientific discern ment that tander the head os Speculative Alchem y he should have formed aclear, though distant Survey, of Chemicat science a S the intermediate link be tween Aristotelian Physics and the scienceos living bodies. As Physics followed on Mathematic s. so Gid

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lxxviii INTRODUCTION

Physics. Aster chemistry came the stud y os living hodies,on whicli Bacon. while assigning to this science iis natural place in the series, has sa id litile or nothing. But on thestu cly os planis and animais was based . under the nanae OfMedicina. the stud y of the Physical structure and functionsos man. Here Bacon had for his gui des not Galen incleed to whom his reseren Ces a re seue, but Avicenna, Haly, anda host of Arabian professors of medicat ari, to whom Galenti ad supplied a very substantial foundation os anatomical and physiological knowledge. Bacon's s hori treatis e. to whichre rence is occasionalty made in the OsnS Majus, De retardandis Senectutis accidesnIMns, wili sufficient ly illustrate his vi eius on this branch of science. X. EXPERIMENTAL SCIENCE. I ast among the series os the natural sciences Comes that whicli Bacon denotes as Scientia EX perimentalis Thesam ple os it sor it can hard ly be regat ded as more thana sample, gi ven in the si Xth Section os the opus Majus indicates that it was connected in Bacon 's mino with no specialde pariment os reSearch, hut was a generat method used forthe dotable purpose os controlling reSulis at ready reached by mathematical procedure. and of Stimulat ing new reSearches inhelds not as 3 et opened to inquii X. In so me respectS thi S is the most original part of his work. Not that eXperiment was a new thing. EX periments without number had been made by man frona the time of his first APPearance On the planet. The Greelis towarcis the end of their marvel lotis scientific career had begun to u se e X peri montin their investigations os natural truth. Galen had applied itin his researches into the nervo us system ; Ptolemy had arrived by iis means at his remari able disco very of the refractiori oflight. The Arab astrono mers, far more si ii sui mechanicians than the Greel f had constructed extrem ely elaborate apparatu Ssor the Same purpOSe, and also to veri sy the equali ty of the angi es of inciden ce and reflection. But no one bes ore Bacontiaci abstracted the method os experiment Do in the concrete

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ΕXPERIMENTAL METHOD.

problem, and had seen iis bearing and importance RS a Universat method os research. Implicit ly men os science hadbegian to recogniZe the Vatiae of eXPeriment. What Bacondid was to mal e the recognition eXplicit. EXPeriment took iis place as a distinct depariment Os philosophy. What mal es this result peculiarly remari able is that it was reached by a thini er who was so pro sotandi y penetraled by the mathematical spirit. In this matter Roger Bacon Comparessavourably with his illustrious namesal e of the spuenteenthcentUry, who wholly falled to appreciate the impori of mathematical method. He rises to the leUel os one greater than ei ther the author of the Disconrs Sur la naeuodes. ForDeSCartes as for Roger Bacon, mAthematicS was clavis Scientiarum, the key to the temple of Science. But it was held by both alii e that eXperiment was needed to carry out the researches whicli mathematical deduction had suggested ;and that, as each science gre , the Share talien by e X periment

in itS progress was to beco me more and more Predominant. I. MORAL PHILOSOPHU.

Last in order, both in the opus Majus and in the Scriptum

it can be made to go in support of the articles of the Catholicsaith. Theology, says Aquinas S. T. ParS I. QuaeSt. i. Art. 5),USes other sciences as her hancinnat is and assistants. Man is more east ly ted on to things above reason, is he begins withthings whicli reason cara demonstrate. It is triae that Unassis ted reaSon is incompetent to disCOver and demonstrate the doctrine

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l XXX

INTRODUCTION. of the Trinity. Impossibile est,' he says Quaest. XXX ii.

Rrt. I), per rationem naturalem ad Cognitionem Trinitatis divinarum Pea Sonarum porVenire.' But he goes on to eXplain that there a re two modes os employing reason. One is tocli scover and prove a principier AS in physi CS we proVe theuniformi ty os the motion of the heaUens. The seCoiad modeis. when the principie is admitted, to Ahow that certain observe deffecis are consistent With and follow from it. So, sor instance, assum ing the reali ty os our hypotheses as to eccentrices an de Picycles, wO Can Show that the move ments of the planeis talae place in accordance with these hypotheses. It is this laiter form os reasoning that we u se in referen ce to the Trinity. 'Trinitate posita, congruunt hujusmodi rationes 'we finii analogies with this doctrine whon we Consider what

PaSses in Our own minit S. Ipse conceptus cordis de ratione

sua habet quod ab alio procedat, scilicet a notitia concipientis ' QuaeSt. XXXi V. art. l). Quanto aliquid magis intelligitur tanto conceptio intellectualis est magis intima intelligenti et

IVRLiS Uniam . . . Undo cum divinum intelligere sit in fine persectioni S . . . neceSSO CSt quod Verbum divinum sit perfecte Unum C tam eo a quo Procedit, absque omni diversitate ' Quaest.

XXV ii. art. Ι). Similarly art. A), the procession os the Thirci Person is likened to the operation of the will which we cali inhuman beings love. Processio Uerbi attenditur secundum actionem intelligibilem. Secundum autem operationem Voluntatis invenitur in nobi S quaedam alia proceSSio, Scilicol proceSSio amori S, SOCund Um quam amnium CSt in amante, Si Cut per Conceptionem Verbi res dicta vel intellecta est in intelligente. Unde Ct, Praeter ProceSSionem Verbi, ponitur alia processio in divinis, quae CSt Processio amoris UERCon RS we might CXPOCt, was not less eager to find the mysteries of revelation restia lowed by human reason.

y It is perhaps hard ly nCcessary to refer in this connexion to Hampclen siectures on Thc Scholastic Philosopis consideria in iis relasion to Christian heolo . Compare p. 8r second edition), The object of the Scholastic Theology was to deieci and dra forti, froin the Scripturo, hy aid of the subile analysis of the philosophy of Aristotio, the mysticat trullis of God on whichthe Sci ipture Revelation was conceived to be founded. '