travels freely ihroua^h bodies '^' and especially mat;- 

 netic bodies;''" one can understand the action of 

 the armature on tliis basis. "* Since coition cannot 

 be prevented by shieldins?, it must have an imma- 

 terial cause. '^' 



Yet, unless one has the oeeult action-at-a-distance, 

 ehan?;e must be caused by contact forces. Gilbert 

 resolved the paradox of combining contact forces 

 with forces tiiat cannot bi- shielded, by passing to 

 a higher level of aljstraction for the explanation of 

 magnetic phenomena: he saw the contact as that of 

 a form with matter. 



Although Gilbert remarked that the cause of mag- 

 netic phenomena did not fall within any of the cate- 

 gories of the formal causes of the Aristotelians, he 

 did not renounce for this reason the medieval tradi- 

 tion. Actually there are many similarities between 

 Gilbert's explanation of the loadstone's powers and 

 that of St. Thomas. Magnetic coition is not due to 

 any of the generic or specific forms of the .Aristo- 

 telian elements, nor is it due to the primary qualities 

 of any of their elements, nor is it due to the celestial 

 "generans" of terrestrial change. ^'^ 



Relictis aliorum opinionibus dc magiiclis alliactione; 

 nunc coitionis illius rationem. ct motus illius commoNcmcm 

 naturain docebimus. Cum vero duo sint corporuin genera, 

 quae manifestis sensibus nostris molionibus corpora ailicere 

 videntur, Electrica et Magnetica; Electrica naturalibus ab 

 humore effluviis; Magnetica formalibus cfRcienliis, seu 

 potius priinariis vigoribus. incitaliones faciunt. l''onna 

 ilia singularis est, el peculiaris, non Peripalelicoruin causa 

 formalis, et specifica in mi.xtis, est sccunda forma, non 

 generanlium corporum propagatrix; sed primorum el 

 praeciporum globorum forma; et partium corum homo- 

 genearum, non corruptarum, propria enlilas et e.\islentia, 

 quam nos primariam, et radiealcm, et astream appellare 

 possumus formam; non formam primam Aristolelis; sed 

 singularem illam. quae globum suum proprium tuclur ct 

 disponit. Talis in singulis globis. Sole, lunas ct astris, est 

 una; in terra ctiam una, quae vera est ilia potenlia mag- 

 netica, quam nos primarium vigorem appellamus. Quare 

 magnetica natura est telluris propria, eiusque omnibus 

 verioribus partibus, primaria ct stupenda ratione, insita; 

 haec ncc a cacio toto dcrivatur procreaturve, per sym- 

 pathiam, per influentiam, aut oceultiores qualitates; ncc 

 peculiar! aliquo astro: est enim suus in tcllure magncticus 



'" M: pp. 106, 107, 108, 114, 134, 136, 140, 162. 

 i"M: pp. 106, 109, 114, 159, 162. 

 ""M: pp. 137-140. 

 '" M: p. 109. 

 "« M: p. 

 ch. 4, p. 65. 



109. 



105, and Gilbert, De magncle, London, 1600, bk. 



vigor, sicut in sole ct luna suae formae; frustulumquc; 

 lunac, lunaticc ad cius tcrminos, ct formam compxanit se; 

 soiarque; ad solcm, sicut magnes ad tellurcm, ct ad altcrum 

 magnetem, secundum naturam scse inclinando ct alliciendo. 

 Differendum igilur dc tcllure quae magnetica, et magnes; 

 lum etiam dc partibus eius verioribus, quae magnelicae 

 sunt; et quomodo ex eoilione difficiuntur. 



Instead, he declared it to be due to a form that is 

 natural and proper to that element that he made the 

 primary component of the earth."" 



To understand his argument, let us briefly recall 

 the peripatetic theory of the elements. In this philos- 

 ophy of nature each element or simple body is a 

 combination of a pair of the four primary qualities 

 that informs inchoate matter. These qualities arc the 

 instruments of the elemental forms and determine 

 the properties of the element. Thus the element fire 

 is a compound of the qualities hot and dry, and the 

 substantial form of fire acts through these qualities. 

 .Similarly for the other elements, earth, water, and 

 air: their forms determine a proper place for each 

 element, and a motion to that place natural to each 

 element.'^" 



Gilbert had previously declared that the primary 

 substance of the earth is an element. Since it is an 

 element, it has a motion natural to it, and this motion 

 is magnetic coition. As an Aristotelian considered 

 the substantial form of the element, fire, to act 

 through the qualities of hot and dry, and to cause 

 an upward motion; so Gilbert argued that the sul)- 

 stantial form of his element, pure loadstone, acts 

 through the magnetic qualities and causes magnetic 

 coition. This motion is due to its primary form, and 

 is natural to the element earth.'*' It is instilled in all 

 |)ri)per and undegenerate parts of the earth,"'' but 

 in no other element.'" 



To the medieval philosopher, the '"generantia" of 

 the occult powers of the loadstone are the heavenly 

 bodies. Gilbert, however, endowed the earth with 

 these heavenly powers which were placed in the 

 earth in the beginning '" and caused all magnetic 

 materials to conform with it both phvsicallv and 



"9 M: p. 105. 



'" M: pp. 289, 322. 



n' M: pp. 26, 68, 105, 179, 198, 307, 335, 343. I'or rotation, 

 sec footnote 147. 



'*- M: pp. 67, 71. That cacli part is inlbrnu-d widi il\c 

 properties of the whole is an argument favoring an animistic 

 explanation of the nature of this form. 



'« M: p. 109. 



i« Nf: p|i. m, ISS. 



PAPER 8: N.\TUR.\L PHILOSOPHY OF VVILLLA.M GILBERT 



135 



