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on, whicli is specialty potent, and has the greateSt penetrative power. It is to be noted that rays proceed ing stom a Very di Stant so urce appear parallel, though in reali ty they are not So : so the walis ofa house seem parallel to each other, though in reali ty each is directe dio the centre of the earth 494 498
Optical principies leach us that in looking at a sphere the visualcone embraces tess than half the Suriace. In considering the portionos a convex or ConCAVe Suriace that Can be illumina ted by a fource oflighi, we have to determine to What portion Os it rectilinear rays Canproceest Dom the illuminat ing poliat Without impediment. In the mutuat action of two Spheres, more than half the sursace of the smaller
But the species has no dimensions other than those of the medium in Whicli it is generate d. During the generation os species Dom themedium, the medium does not lose iis Corporeat Character, nor i S anynew body created or added. The Species is simply a portion of the medium wrought on in a peculiar way by the agent. Though soWTOUght On RS to resemble the agent, yet the substance of whicli it is formed is that of the medium ....... 502-504But the species moves on ard in space, while the medium rema insat reSt: how can the species be said to have the bo dily substance of the medium y The reply is that the species successively formed arenot numeri catly identi cal. What tal es place is the suCCeSSive generation hom po in t to potnt of Something new, a S in the Case of a Ahadowapparently Shisting iis position, but Whicli is reatly being conStantlyrene ed. It is asked why does not the movement of the air by vindassect the direction of the species 8 The reply is that the force exerted by the agent is in a definite direction and rene S the Specie Sin eaCh portion of air as it is dri ven by. In the Case, again, os refleX-ion, there is no violent casting back of the species : it Simply purSueSthe only path possibi e to it. What we cali species is not orae identi cal
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clxxxii A LYSIS MULTIPLICATION OF SPECIES.
The second question is whether the Species os a corporeat agentshould be regarded as corporeal or spiritual. Clearly the former: since it is not a foui, Or an intelligetice, or a tirst Cause; and theseonly can be considerest aS spiritual. The species must be of like nature with the agent, and of like nature with the completed effeci. It cannot be of nobter nature than that whicli generates it. Some holuthat, though in itS essenCe Corporeat, yet iis mode os existence is spiritual. But there cannot be this disparaten esS between the essen eand the mode os existerice. The esSenCe of the Species has dimen Sion, derived as we have Seen Dom the medium ; it i S there re Corporeat. It is salo that it has not material essence material being here taliensor corporeat j. But Oven Spiritual SubStanCeS have material essence: they are Compoundeo os forin and of matter: much more, there sore, are SpeCies materiai. It has been at ready shown that thespecies of Corporent SubStunce resembles the total compound. In the medium not mei ely is the formal essenee generaled but themateriai, although the essence be in Complete. I therefore conclude that the species of a Corporeal object i S corporeat . . . 507 509 The Contrary View has arisen from imperfeci translations of Aver-roes, Avicenna, Znd Aristolle. In theSe the word insensibie has been mista ken for immateriai. Anu because Spirituat things are insensibie, therelare What is insensibie has been tinen to mean spiritual anclina materiai. It is objected that species are not always in Sen Sible, a Swhen a rny passeS through n window or through coloured glass. Butthis is only accidental. Some expreSSi Ons of Avicenna as to the reception os impressions in the brain have been wrongly interpreted. They must be talien in Connexion with what Aristolle has said on the
SAmo Sulla CCt .......... 509-511
I pass to the question of the mingling of Species in the medium. The question is one of much dissicut ty, but Ptolemy and Alli agenthrow great light upon it. Species of the fame hind meli into one,
and is opposite, then the Stronger overwheims the wenker. Thosethat are contingent, i. e. have no relation to eaCh Other, CO-exi St
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separat ely. Species in laci aci in this respect aS do their a genis, and as do their completed esseCis. Athagen thus explains the uni tyof impression resulting Dona species of an object entering the twoeyes ; they are uni ted in the brain. Eut is species are thus mixed, ho do we reCognige Various objecis as distinctῖ Because throughthe potnt of mixture sonae rays Come perpendicularly froni the objectio the eye, o thers come to this poliat obliquet y; theSe lalter areeclipsed by the former. we may remarii further that the Variotis partS of the agent are always active the generation of the speciesi S there re continuou S. Species urare lated to One another do notCommingle; they eXi Si separalely and Simultaneousty . . 5ll-516
We have no v to consider how and why Species are wenkened in their transit. Is there resistance in the medium 8 There is. ForeVery agent produces rarefaction and Condensation, as the firSt processin every natural action. What is raro re Si StS CondenSation. Anci Con- VerSely. Theres ore eUery medium offers reSi Stance. Further, thereis a practical limit to rarefaction. It may be Sald that resistance isonly offered by Contraries, and that, to many agent S generatingspecieS, nothing i S Contrary, in the sense in xvhicli dari ness is contra to light. Lut the resistance is not to the species them Selves, butto the proceSSeS of rarefaction Or CondenSation whi Ch aCCompany
It is obvious that species, So long as they Continue to radiate, andare not arreSted by an accumulation of Such materiai as will intensis ytheir action as in the Case of sire acting on fuel), are weakened by distance. The senses are leSS affected by a cli stant than a near Objeci. Two causes may be assigne d. It is sald to be a law that as the first species is wenker than the agent, so the SeCond is wenkerthan the firSt, and so on. This, however, is not invariabie. I f ironbe held ut so me distance frona a magnet, the iron is more asseCted than the air belween them. So a ray, paSSing through Coloured glaSS, ProduceS a Stronger effect on a distant wali than on the intermediate uir. Another reason may be assigned. The agent radiates force in ali directions. Mucii force is dispersed thuS. And though, for SpecialreaSons, the force in any one line may be found not to grow weaher, yet it Will be so where the medium is ordinari ly pervioli S. ThuS both distance and radiant dispersion a Count for the wealiening of SpecieS.
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clxxxi v A LYSIS MULTIPLICATION OF SPECIES.
When the direction os radiation is froin terrestriat to celestiat, it might be thought that the in creasing rari ty of the medium would compensate the wenkening of the specieS frona dispersion; but the
Supposing space were uni imited, Could multiplication os species goon indefinitely ῖ No ; for, aS we have Seen, the SpeCiOS grows Continualty weaker the further it is hom itS Source. Is the supply of matter On whicli it could operate were infinite, then no dotibi thea tion would be infinite ; but this is not the Case. It might be said that, since matter is infinitely divi Sible, there Would always rem insomething on whicli the species, however en ebled by distance, coulo aci; that therefore the duration of the action would be infinite. But this Seems a forced ano vn Satisfactory Conclusion. Again, it might be urged that the medium may grow Continually more subile soas to correspond to the continuat wenkening of the species. Put this does not in f Ct talae place. AS a faCt, the reSi Stance, in Our worid, whicli is finite, is always sum cient to prevent the species Dompassing beyond a certain distanee 521 524Supposing the existence of a vacuum het ween earth and heaven, no species Could radiate ; for no natural action Can talae place ina vacuum. It follows also that beyono the ninth and tentii heavens no Species frona the starS Can radiate. For beyond these there is nothing, not even empty Space 524 525
The radiation of force takes place in time. For it involves Change in the medium; and Change involves time. When the path of propagation i S refracteo, more time is talien than when the path is direct. Finite force cannot aci instantaneously, for then it would beequat to infinite force. As a pol ni is to an instant, so is a line toti me. The passage of a poliat is instantaneous, in the passage of a lineti me is occupi ed. Translation implies besore and after . . 525-526 It is said that the transit os light is instantaneous. But ali that is meant is that the time required is insensi ble. Aristolle, in sayingiliis, is arguing against Empedocles, who regarded light as a substance flowing froni the luminous body. In this case no doubt we should beable to see iis passage froin east to west in the heavens. But thevi eiu here talien os light is not that it is a body translated, buta moUement continuouSty Propagated. Aristolle no doubi dis-
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tinguishes the propagation os light Dom that os Sounds or odours. But the distinction is os degree ; light be ing more subile, iis motion
Alli indi urges that, though through shori distances the transit oflight may be imperceptibi e to our senses, yet that the Summation offfiori periods would amount, in the transit Dona enSt to weSt, to Something that would be percepti ble. But os imperceptibili ty there are many degrees; and the propagation os light is so rapid that the Summation Os a vast number of imperceptibi e periods may stili notre Ch the pol ni at whicli perception os time by human Sense isPOSSible . 528 It is further maintained that in radiation os species, aS here described, more time would be occupied than in translation os a body throughspace : beeauSe bet een the formation of any one Species and the formation of that whicli follows it, there is an intervat os rest. ThelaCt is, however, that the resistance of the medium to a body Carrie dthrough it would be far greater than it would be to the formationos Species, whicli involves an exceed ingly slight disturbance of the medium ; so that the motion in this laiter Case will be far more rapid, and the interposition os intervals of rest will pass unperceived . 528 529
The path os Some species falis perpendicularly on the objeci; these
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clxxxvi A LYSIS MULTIPLICATION OF SPECIES.
refracted ray is stronger than the reflected, iis path lying nearer tot he direct perpendicular ray. The ray refracted by paSSage Doma denser to a rarer medium is legS potent, for the Same reason, thanthe Tay refracted stom rarer to denser. In the case of reflected rays, those that malae an angle with the vertical line produce a greater effect than those that sali vertically; not merely because they divergetess stom the direct ray, but be cause they Can be accumulated by suit ably shaped mirrors. Some of these are described, thoughI have not myself Seen them, which bring rays to a focus both in front
Cones of rays Come Dom the agent to each part of the sursace ac ted on. The shorter the cone, the Stronger is the action. Theshortest cone is thus defined. Let a Circle be drawn in the agent sphere divi ling iis operative hom iis inoperative part. From any potnis in the circumference of this circle let diameters of the spherebe drawn. Tangenis to the sphere at the extremities of thesediameterS wili forin the shortest Cone. Other potnis Connected with this subjeci are illustraled by the accompanying diagranis . 539-543
When the generating agent is remoVed, does the Species at oncedisappear Θ Not in Stantaneously, but gradually, hom the Causes stateclin the previ ous Chapter. The apparent permanen Ce in Some CaSeS of the Specie S, after the agent has di Sappeared, is to be explained. The Semen retains iis force in the absence of the male parent; but herethe feniale supplies the place. A heated stone retains iis heat. Herethe SpecieS, i. e. incomplete effeci, has pasSed into a more complete
CHAPTER III. Are the rei terat ed actions of the agent On the patient to be regardedas numeri catly identicat, or aS distinct Θ They must be regarded as
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distinct. There is no question here of anything being created. The action and motion are not fixed ano permanent things, but SuCCeSsOry. Is a box be made and then talien to pieCeS, and SubSequently puttogether again, we consider that it lias been twice made, althoughOut of the Same materint ........ 547-549
In a transparent medium, does the first species Continue during the Pre Selace of the agent, or is it destroyed and rene wed Z Thel alter is the Case. There is far more rapid dispersion in a rare thalain a dense medium. In Certain region S, as in the tropical gone Where the sun is vertical for a ConSiderable time, there is tess rapid an clcomplete dispersion. Mucii depends on the nature of the hodya ted on. Dense bodies retain the effect ir a longer time than rare. The foregoing remarks apply to terrestriai and Corporeat things.
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FRATRIS ROGERI BACONORDINIS MINORUM; OPUS MAJUS. PARS PRI MAHUJUS PERSUASIONIS
IN qua eXcluduntur quatuor universales cata Sae totius ignorantiae humanae, habens quatuor distinctiones. In prima Sunt quatuor capitula. In primo data totius persuasionis intentione reprobantur illae quatuor Causae uniVersali Sermon C. CAPITULUΜ I. Sapientiae persecta Consideratio consistit in duobus, Videlicet, ut videatur quid ad eam requiritur, quatenus Optime sciatur; deinde quomodo ad Omnia comparetiar, Ut Per eam modis congruis dirigantur. Nam per lumen Sapientiae ordinatur Ecclesia Dei. Respublica fidelium disponitur, infidelium
ConUOrSio procuratur; et illi, qui in malitia obstinati sunt, Valent per Virtutem sapientiae reprimi, ut melius a finibus Ecclesiae longiuS pellantur quam per effusionem sanguini SChristiani. Omnia vero quae indigent regimine sapientiae ad haec quatuor reducuntur; nec pluribu S PoteSt Comparari. De hac igitur sapientia tam relate quam absolute Scienda nunc, Secundum tenorem epistolae in , quicquid poSsim Circa
φ Epistolae praecedentis, Cottonian MSS., Jul. D. V. hereaster referred to as Jul A This was the letter of Pope Clement IV. It ran thUS : Dilecto filio Fratri Rogerio dicto Baccon ordinis Fratrum Minorum. Tuae devotionis literas gratanter recepimus, sed et verba notavimuS diligenter
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PerSuasionem ad praesens Vestrae Eeatitudini praesentare conabor. Quoniam autem illa, de quibus agitur, sunt grandia et insolita, gratiam et favorem humanae fragilitatis requirunt. Nam secundum Philosophum septimo Metaphysicae, ea quae
Sunt maXimae cognitionis Secundum SO, Sunt minimae RPPrChen Sionis quoad nos. Involuta enim veritas in alto latet et in Profundo posita est, ut dicit Seneca septimo de beneficiis, et quarto Naturalium. Et Marcus Tullius in Hortensio dicit, quod omnis noster intellectus multis obstruitur difficultatibus quoniam ipse se habet ad manifestissimum in sua natura, Sicut O CUJUS noctuae et vespertilionis ad lucem solis, ut Philosophus dicit secundo Metaphysicae, et Velut surdus a natiVitate ad delectationem harmonicam, sicut undecimo Metaphysicae dicit AVicenna. Quapropter sufficit nobis in inquisitione Veritatis proprii intellectus imbecillitas, ut quantum POSSU IDUS CRUSAS
et OCCASiones erroris eXtraneas longius a debilitate sensus nostri relegem US. Eour causes Quatuor Vero Sunt m a Nima comprehendendae Veritatistiti ori y Offendicula, quae Omnem qUCm Cumque Sapientem impediunt custom, et ViX aliquem permittunt ad Uerum titulum Sapientiaepi εjudiee, PerVenire, Videlicet fragilis et indignae auctoritatis exem P ζ VmP 'lum, consuetudinis diuturnitas, Vulgi sen Sus imperiti, et
knowledile. ProPriae ignorantiae occultatio cum oStentatione sapientiae apparentis. I Iis omnis homo inVOlVitur, OmniS StatUS occupatur. Nam quilibet in singulis artibus vitae et studii et Omnis negotii tribus pessimis ad eandem Conclusionem utitur argumentis, scilicet, hoc CXemplificat Um CSt per majores,
hoc Con Suetum est, hoc Vulgatum est; ergo tenendum. Sed oppositum Conclusionis longe meliuS Sequitur OX Praemi SSi S, Sicut per auctoritatem et eXperientiam et rationem multi
quae ad explanationem earum dilectus filius G. dictus Eo necor miles viva voce nobis proposuit tam fideliter quam prudenter. Sane ut melius nobis liqueat quid intendas volumus ot tibi per Apostolica Scripta praecipiendo mandamuSquatenUS, non ObStante praecepto praelati cujuScunque contrario vel tui ordinis conStitutione quacunque, opus illud quod te dilecto filio Raymundo de Lauduno communicare rogavimus in minore officio constituti scriptum de bona litera nobis mittere quam citiuS poteris non omittas, et per tuas nobis declares literas quae tibi videnter adhibenda esse remedia circa illa quae nuper esse tanti
discriminis intimasti, et Jaoc quanto secretius poteris facias inclitate. Datum Viterbii x Kalend Julii anno ii.' Wadding, Annales Minorum, Vol. iv, P. 265.