expountlcd at Qjrcalcr Icntflh in his treatise on the 

 soul."'' 



Quod quidciii ex piopiiis roniiaruin opcrationibiis 

 perpcndi potest. I'ormac enim clcmentoiuin, quae sim 

 infimac et maleiiae propinquissimc, non habent aliquain 

 operationem c.xcedentcin qualitates activas ct passivas, ui 

 raium cl densum, et aliae huiusmodi, qui videnlur esse 

 materiae dispositiones. .Super has autcni sunt formae 

 mistorum quae praetcr praediclas operationcs, habeiit 

 aliquam operationem consequcntcm speciem, quam fortiun- 

 tur ex corporibus coelestibus; sicut quod magnes attrahit 

 ferruin non propter calorem aul higiis. aut ahquid huius- 

 modi; sed ex quadam participalione virtulis coelestis. 

 Super has autem formas sint iterum animac plantarum, 

 quae habent simihtudincm non solum ad ipsa corpora 

 coelestia, sed ad motores corporum coelesiium. inquanluiu 

 sunt principia cuiusdam molus, quibusdam seipsa movenli- 

 bus. .Super has autem ulterius sunt animae brutorum, 

 quae similitudinem iam habent ad substanliam moventem 

 coelestia corpora, non solum in operationc qua movent 

 corpora, sed etiam in hoc quod in seipsis cognoseitivae sum, 

 licet brutorum cognilio sit maleriahuni lantiun et ma- 

 terialiter. . . . 



St. Thomas placed the form of the mat!;net and its 

 powers in the hierarchy of forms intermediate be- 

 tween the forms of the inanimate world and the 

 forms of the organic world with its hierarchy of plant, 

 animal and rational souls. The form of the loadstone 

 is then superior to that of iron, which can only act 

 throus^h its active and passive qualities, but inferior 

 to the plant soul, that has the powers of growth from 

 the "virtus cocli." This is similar to Galen's com- 

 parison of the magnet's powers to that of the nutritive 

 powers of organic bodies. 



In his commentary on .Aristotle's P/ijsics, St. Thomas 

 explained how iron is moved to the magnet. It is 

 moved by some quality imjiarted to the iron by 

 the magnet.-' 



lUud ergo irahere diciuir. quod movel aheruni ad 

 seipsum. Movere autem aliquid secundum locum ad 

 seipsum contingit tripliciler. Uno modo sicul finis movel; 

 unde et finis dicitur trahcre, secundum illud poetate: 

 "trahit sua quemque volufjtas"' : et hoc modo potest dici quod 



-• St. Thomas .\quinas, of) cit. (footnote 19), vol. 8, Qimalin 

 unica: de anima, art. 1 (Utrum anima humana possit esse 

 forma et hoc aliquid), p. 437. See also vol. 8, Qiiaeslio: Dr 

 veritate, quaestio 5 (Dc providentia), art. 10 (Utrum human! 

 actus a divina providentia gubcrnentur mcdiis corporibus 

 coelestibus), p. 678. 



" St. Thomas Aquina.s, op. cil. (footnote 19), vol. 2, Physi- 

 corum Arislotelis rxpositio, lib. 7, lect. 3, cap. g (Probatur in 

 motu locali quod movens et motum oportct esse simul), p. 97 

 (quoted in Gilbert, M: p. 104). 



locus trahit id, quod naturaliter movclur ad locum. Alio 

 modo potest dici aliquid trahere, quia movel illud ad 

 seipsum alterando aliqualiter, ex qua altcralionc contingit 

 f|Uod alteralum moveatur secundum locum: et hoc modo 

 magnes dicitur trahcre ferruiti. .Sicul enim generans 

 niovet gravia et levia, inquanlum dat eis formarum per 

 quam movenlur ad locum, ita el magnes dat alicjuam 

 qualitatem ferro, per quam movctur ad ipsum. Et quod 

 hoc sit verum palct ex Iribus. Primo c|uidem quia magnes 

 non trahit ferrum ex quacumque disiantia, sed ex propin- 

 (|Uo; si autem ferruin moveretur ad magnetein solum sicul 

 ad linem, sicut grave ad suum locum, ex qualibet disiantia 

 tenderet ad ipsum. .Secundo, quia, si magnes aliis pcr- 

 ungatur, ferrum atlrahere non potest; cjuasi aliis vim 

 alterativam i|)sius impedientibus, aut eiiam in conirarium 

 alterantibus. Tertio, quia ad hoc quod magnes attrahat 

 ferrum, oporlet prius ferruin liniri cum magnete. ma.\ime 

 si magnes sit parvus; quasi ex magnete aliquam virtulcm 

 ferrum accipial ut ad eum moveatur. Sic igitur magnes 

 attrahit ferrum non solum sicul finis, sed etiam sicul movens 

 et allerans. Tertio modo dicitur alic|uid atlrahere, quia 

 movel ad seipsum motu locali lantum. El sic definilur hie 

 traclio, prout unum corpus trahit alterum, ita quod irahcns 

 simul moveatur cum eo quod trahitur. 



As the "generans" of terrestrial change moves what 

 is light and heavy to another place by implanting 

 a new form in a substance, so the magnet moves the 

 iron by impressing upon it the quality by which it 

 is moved. By virtue of the new quality, the iron is 

 not in its natural place and moves accordingly. 

 .St. Thomas proved that the loadstone acts as a 

 secondary "generans" in three ways: (1) the load- 

 stone produces an effect not from any distance 

 but only from a nearby position (showing that this 

 motion is due to more than place alone), (2) rubbing 

 the loadstone with garlic acts as if it impedes or 

 alters the "virtus magnetis," and (3) the iron must 

 be properly aligned with respect to the loadstone in 

 order to be moved, especially if the loadstone is small. 

 I'hus the iron is moved by the magnet not only to a 

 place, but also by changing and altering it: one has 

 not only the change of locomotion but that of altera- 

 tion. Moreover the source of this alteration in ihe 

 iron is not the heavens but the loadstone. Accordingly 

 the loadstone could cause change in another sub- 

 stance because it could influence the nature of the 

 other substance. 



.\bout the time that St, Thomas was writing his 

 letter De operalionihus occuUis naluraf to a certain 

 knight, Pctrus Peregrinus was writing from a military 

 camp a letter in wliicli he showed how certain rela- 

 ii\elv new eflVcts could be produced by the loadstone. 



PAPER 8: N.VrURAI, PHILOSOPHY OF VVII I IAM (GILBERT 



127 



