Chapter 1

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CONTRIBUTIONS FROM

THE MUSEUM OF HISTORY AND TECHNOLOGY:

PAPER 8

THE NATURAL PHILOSOPHY OF WILLIAM GILBERT AND HIS PREDECESSORS

_W. James King_

By W. James King

THE NATURAL PHILOSOPHY OF WILLIAM GILBERT AND HIS PREDECESSORS

Until several decades ago, the physical sciences were considered to have had their origins in the 17th century--mechanics beginning with men like Galileo Galilei and magnetism with men like the Elizabethan physician and scientist William Gilbert.

Historians of science, however, have traced many of the 17th century's concepts of mechanics back into the Middle Ages. Here, Gilbert's explanation of the loadstone and its powers is compared with explanations to be found in the Middle Ages and earlier.

From this comparison it appears that Gilbert can best be understood by considering him not so much a herald of the new science as a modifier of the old.

THE AUTHOR: W. James King is curator of electricity, Museum of History and Technology, in the Smithsonian Institution's United States National Museum.

The year 1600 saw the publication by an English physician, William Gilbert, of a book on the loadstone. Entitled _De magnete_,[1] it has traditionally been credited with laying a foundation for the modern science of electricity and magnetism. The following essay is an attempt to examine the basis for such a tradition by determining what Gilbert's original contributions to these sciences were, and to make explicit the sense in which he may be considered as being dependent upon earlier work. In this manner a more accurate estimate of his position in the history of science may be made.

[1] William Gilbert, _De magnete, magneticisque corporibus et de magno magnete tellure; physiologia nova, plurimis & argumentis, & experimentis, demonstrata_, London, 1600, 240 pp., with an introduction by Edward Wright. All references to Gilbert in this article, unless otherwise noted, are to the American translation by P. Fleury Mottelay, 368 pp., published in New York in 1893, and are designated by the letter M. However, the Latin text of the 1600 edition has been quoted wherever I have disagreed with the Mottelay translation.

A good source of information on Gilbert is Dr. Duane H. D. Roller's doctoral thesis, written under the direction of Dr. I. B. Cohen of Harvard University. Dr. Roller, at present Curator of the De Golyer Collection at the University of Oklahoma, informed me that an expanded version of his dissertation will shortly appear in book form. Unfortunately his researches were not known to me until after this article was completed.

One criterion as to the book's significance in the history of science can be applied almost immediately. A number of historians have pointed to the introduction of numbers and geometry as marking a watershed between the modern and the medieval understanding of nature. Thus A. Koyré considers the Archimedeanization of space as one of the necessary features of the development of modern astronomy and physics.[2] A. N. Whitehead and E. Cassirer have turned to measurement and the quantification of force as marking this transition.[3] However, the obvious absence[4] of such techniques in _De magnete_ makes it difficult to consider Gilbert as a founder of modern electricity and magnetism in this sense.

[2] Alexandre Koyré, _Études galiléennes_, Paris, 1939.

[3] Alfred N. Whitehead, _Science and the modern world_, New York, 1925, ch. 3; Ernst Cassirer, _Das Erkenntnisproblem_, ed. 3, Berlin, 1922, vol. 1, pp. 314-318, 352-359.

[4] However, see M: pp. 161, 162, 168, 335.

There is another sense in which it is possible to contend that Gilbert's treatise introduced modern studies in these fields. He has frequently been credited with the introduction of the inductive method based upon stubborn facts, in contrast to the methods and content of medieval Aristotelianism.[5] No science can be based upon faulty observations and certainly much of _De magnete_ was devoted to the destruction of the fantastic tales and occult sympathies of the Romans, the medieval writers, and the Renaissance. However, let us also remember that Gilbert added few novel empirical facts of a fundamental nature to previous observations on the loadstone. Gilbert's experimental work was in large part an expansion of Petrus Peregrinus' _De magnete_ of 1269,[6] and a development of works like Robert Norman's _The new attractive_,[7] in which the author discussed how one could show experimentally the declination and inclination of a magnetized needle, and like William Borough's _Discourse on the variation of the compass or magnetized needle_,[8] in which the author suggested the use of magnetic declination and inclination for navigational purposes but felt too little was known about it. That other sea-going nations had been considering using the properties of the magnetic compass to solve their problems of navigation in the same manner can be seen from Simon Stevin's _De havenvinding_.[9]

[5] For example, William Whewell, _History of the inductive sciences_, ed. 3, New York, 1858, vol. 2, pp. 192 and 217; Charles Singer, _A short history of science to the nineteenth century_, Oxford, 1943, pp. 188 and 343; and A. R. Hall, _The scientific revolution_, Boston, 1956, p. 185.

[6] _Petri Peregrini maricurtenis, de magnete, seu rota perpetui motus, libellus_, a reprint of the 1558 Angsburg edition in J. G. G. Hellmann, _Rara magnetica_, Berlin, 1898, not paginated. A number of editions of Peregrinus, work, both ascribed to him and plagiarized from him, appeared in the 16th century (see Heinz Balmer, _Beiträge zur Geschichte der Erkenntnis des Erdmagnetismus_, Aarau, 1956, pp. 249-255).

[7] Hellmann, _ibid._, Robert Norman, _The newe attractive, containyng a short discourse of the magnes or lodestone, and amongest other his vertues, of a newe discovered secret and subtill propertie, concernyng the declinyng of the needle, touched therewith under the plaine of the horizon. Now first founde out by Robert Norman Hydrographer_. London, 1581. The possibility is present that Norman's work was a direct stimulus to Gilbert, for Wright's introduction to _De magnete_ stated that Gilbert started his study of magnetism the year following the publication of Norman's book.

[8] Hellman, _ibid._, William Borough, _A discourse of the variation of the compasse, or magneticall needle. Wherein is mathematically shewed, the manner of the observation, effects, and application thereof, made by W. B. And is to be annexed to the newe attractive of R. N._ London, 1596.

[9] Hellman, _ibid._, Simon Stevin, _De havenvinding_, Leyden, 1599. It is interesting to note that Wright translated Stevin's work into English.

Instead of new experimental information, Gilbert's major contribution to natural philosophy was that revealed in the title of his book--a new philosophy of nature, or physiology, as he called it, after the early Greeks. Gilbert's attempt to organize the mass of empirical information and speculation that came from scholars and artisans, from chart and instrument makers, made him "the father of the magnetic Philosophy."[10]

[10] As Edward Wright was to call him in his introduction.

Gilbert's _De magnete_ was not the first attempt to determine the nature of the loadstone and to explain how it could influence other loadstones or iron. It is typical of Greek philosophy that one of the first references we have to the loadstone is not to its properties but to the problem of how to explain these properties. Aristotle[11] preserved the solution of the first of the Ionian physiologists: "Thales too ... seems to suppose that the soul is in a sense the cause of movement, since he says that a stone has a soul because it causes movement to iron." Plato turned to a similar animistic explanation in his dialogue, _Ion_.[12] Such an animistic solution pervaded many of the later explanations.

[11] Aristotle, _On the soul_, translated by W. S. Hett, Loeb Classical Library, London, 1935, 405a20 (see also 411a8: "Some think that the soul pervades the whole universe, whence perhaps came Thales' view that everything is full of gods").

[12] Plato, _Ion_, translated by W. R. M. Lamb, Loeb Classical Library, London, 1925, 533 (see also 536).

That a mechanical explanation is also possible was shown by Plato in his _Timaeus_.[13] He argued that since a vacuum does not exist, there must be a plenum throughout all space. Motion of this plenum can carry objects along with it, and one could in this manner explain attractions like that due to amber and the loadstone.

[13] Plato, _Timaeus_, translated by R. G. Bury, Loeb Classical Library, London, 1929, 80. It is difficult to determine which explanation Plato preferred, for in both cases the speaker may be only a foil for Plato's opinion rather than an expression of these opinions.

Another mechanical explanation was based upon a postulated tendency of atoms to move into a vacuum rather than upon the latter's non-existence. Lucretius restated this Epicurean explanation in his _De rerum natura_.[14] Atoms from the loadstone push away the air and tend to cause a vacuum to form outside the loadstone. The structure of iron is such that it, unlike other materials, can be pushed into this empty space by the thronging atoms of air beyond it.

[14] Lucretius, _De rerum natura_, translated by W. H. D. Rouse, Loeb Classical Library, London, 1924, bk. VI, lines 998-1041.

Galen[15] returned to a quasi-animistic solution in his denial of Epicurus' argument, which he stated somewhat differently from Lucretius. One can infer that Galen held that all things have, to a greater or lesser degree, a sympathetic faculty of attracting its specific, or proper, quality to itself.[16] The loadstone is only an inanimate example of what one finds in nutritive organs in organic beings.

[15] Galen, _On the natural faculties_, translated by A. S. Brock, Loeb Classical Library, London, 1916, bk. 1 and bk. 3. A view similar to this appeared in Plato, _Timaeus_, 81 (see footnote 13).

[16] This same concept was to reappear in the Middle Ages as the _inclinatio ad simile_.

One of the few writers whose explanations of the loadstone Gilbert mentioned with approval is St. Thomas Aquinas. Although the medieval scholastic philosophy of St. Thomas seems foreign to our way of thinking, it formed a background to many of Gilbert's concepts, as well as to those of his predecessors, and it will assist our discussion to consider briefly Thomist philosophy and to make its terminology explicit at this point.[17]

[17] The background for much of the following was derived from Annaliese Maier, _An der Grenze von Scholastik und Naturwissenchaft_, ed 2, Rome, 1952.

In scholastic philosophy, all beings and substances are a coalescence of inchoate matter and enacting form. Form is that which gives being to matter and which is responsible for the "virtus" or power to cause change, since matter in itself is inert. Moreover, forms can be grasped intellectually, whence the nature of a being or a substance can be known. Any explanation of phenomena has to be based upon these innate natures, for only if the nature of a substance is known can its properties be understood. Inanimate natures are determined by observation, abstraction, and induction, or by classification.[18]

[18] St. Thomas' epistemology for the natural inanimate world was based upon Aristotle's dictum: that which is in the mind was in the senses first.

The nature of a substance is causally prior to its properties; while the definition of the nature is logically prior to these properties. Thus, what we call the theory of a substance is expressed in its definition, and its properties can be deduced from this definition.

The world of St. Thomas is not a static one, but one of the Aristotelian motions of quantity (change of size), of quality (alteration), and of place (locomotion). Another kind of change is that of substance, called generation and corruption, but this is a mutation, occurring instantly, rather than a motion, that requires time. In mutation the essential nature is replaced by a new substantial form.

All these changes are motivated by a causal hierarchy that extends from the First Cause, the "Dator Formarum," or Creator, to separate intellectual substances that may be angels or demons, to the celestial bodies that are the "generantia" of the substantial forms of the elements and finally to the four prime qualities (dry and wet, hot and cold) of the substantial forms. Accidental forms are motivated by the substantial forms through the instrumentality of the four prime qualities, which can only act by material contact.

The only causal agents in this hierarchy that are learned through the senses are the tangible qualities. Usually the prime qualities are not observed directly, but only other qualities compounded of them. One of the problems of scholastic philosophy was the incorporation, into this system of efficient agents, of other qualities, such as the qualities of gravity and levity that are responsible for upward and downward motion.

Besides the causal hierarchy of forms, the natural world of St. Thomas existed in a substantial and spatial hierarchy. All substances whether an element or a mixture of elements have a place in this hierarchy by virtue of their nature. If the material were removed from its proper place, it would tend to return. In this manner is obtained the natural downward motion of earth and the natural upward motion of fire.

Local motion can also be caused by the "virtus coeli" generating a new form, or through the qualitative change of alteration. Since each element and mixture has its own natural place in the hierarchy of material substances, and this place is determined by its nature, changes of nature due to a change of the form can produce local motion. If before change the substance is in its natural place, it need not be afterwards, and if not, would then tend to move to its new natural place.

It will be noted that the scholastic explanation of inanimate motion involved the action and passion of an active external mover and a passive capacity to be moved. Whence the definition of motion that Descartes[19] was later to deride, "motus est actus entis in potentia prout quod in potentia."

[19] René Descartes, _Oeuvres_, Charles Adam and Paul Tannery, Paris, 1897-1910, vol. 2, p. 597 (letter to Mersenne, 16 Oct., 1639), and vol. 11 (Le Monde), p. 39. The original definition can be found in Aristotle, _Physics_, translated by P. H. Wickstead and F. M. Cornford, Loeb Classical Library, London, 1934, 201a10. Aquinas rephrases the definition as "_Motus est actus existentis in potentia secundum quod huius modi._" See St. Thomas Aquinas, _Opera omnia_, Antwerp, 1612, vol. 2, _Physicorum Aristotelis expositio_, lib. 3, lect. 2, cap. a, p. 29.

We have seen above that the "motor essentialis" for terrestial change is the "virtus coeli." Thus the enacting source of all motion and change is the heavens and the heavenly powers, while the earth and its inhabitants becomes the focus or passive recipient of these actions. In this manner the scholastic restated in philosophical terms the drama of an earth-centered universe.

Although change or motion is normally effected through the above mentioned causal hierarchy, it is not always necessary that actualization pass from the First Cause down through each step of the hierarchy to terminate in the qualities of the individual being. Some of the steps could be by-passed: for instance man's body is under the direct influence of the celestial bodies, his intellect under that of the angels and his will under God.[20] Another example of effects not produced through the tangible prime qualities is that of the tide-producing influence of the moon on the waters of the ocean or the powers of the loadstone over iron. Such causal relations, where some members of the normal causal chain have been circumvented, are called occult.[21]

[20] St. Thomas Aquinas, _op. cit._ (footnote 19), vol. 9, _Summa contra gentiles_, lib. 3, cap. 92 (Quo modo dicitur aliquis bene fortunatus et quo modo adjuvatur homo ex superioribus causis), p. 343.

[21] St. Thomas Aquinas, op. cit. (footnote 19), vol. 17 _Opuscula, De operationibus occultis naturae ad queindam militem ultramontem_, pp. 213-224.

While St. Thomas referred to the loadstone in a number of places as something whose nature and occult properties are well known, it was always as an example or as a tangential reference. One does not find a systematic treatment of the loadstone in St. Thomas, but there are enough references to provide a fairly explicit statement of what he considered to be the nature of the magnet.

In one of his earliest writings, St. Thomas argued that the magnet attracts iron because this is a necessary consequence of its nature.[22]

Respondeo dicendum, quod omnibus rebus naturaliter insunt quaedam principia, quibus non solum operationes proprias efficere possunt, sed quibus etiam eas convenientes fini suo reddant, sive sint actiones quae consequantur rem aliquam ex natura sui generis, sive consequantur ex natura speciei, ut magneti competit ferri deorsum ex natura sui generis, et attrahere ferrum ex natura speciei. Sicut autem in rebus agentibus ex necessitate naturae sunt principia actionum ipsae formae, a quibus operationes proprie prodeunt convenientes fini....

Due to its generic form, the loadstone is subject to natural motion of place of up and down. However, the "virtus" of its specific form enabled it to produce another kind of motion--it could draw iron to itself.

Normally the "virtus" of a substance is limited to those contact effects that could be produced by the form operating through the active qualities of one substance, on the relatively passive qualities of another. St. Thomas asserted the loadstone to be one of these minerals, the occult powers of whose form goes beyond those of the prime qualities.[23]

Forma enim elementi non habet aliquam operationem nisi quae fit per qualitates activas et passivas, quae sunt dispositiones materiae corporalis. Forma autem corporis mineralis habet aliquam operationem excedentem qualitates activas et passivas, quae consequitur speciem ex influentia corporis coelestis, ut quod magnes attrahit ferrum, et quod saphirus curat apostema.

That this occult power of the loadstone is a result of the direct influence of the "virtus coeli" was expounded at greater length in his treatise on the soul.[24]

Quod quidem ex propriis formarum operationibus perpendi potest. Formae enim elementorum, quae sint infimae et materiae propinquissime, non habent aliquam operationem excedentem qualitates activas et passivas, ut rarum et densum, et aliae huiusmodi, qui videntur esse materiae dispositiones. Super has autem sunt formae mistorum quae praeter praedictas operationes, habent aliquam operationem consequentem speciem, quam fortiuntur ex corporibus coelestibus; sicut quod magnes attrahit ferrum non propter calorem aut frigiis, aut aliquid huiusmodi; sed ex quadam participatione virtutis coelestis. Super has autem formas sint iterum animae plantarum, quae habent similitudinem non solum ad ipsa corpora coelestia, sed ad motores corporum coelestium, inquantum sunt principia cuiusdam motus, quibusdam seipsa moventibus. Super has autem ulterius sunt animae brutorum, quae similitudinem iam habent ad substantiam moventem coelestia corpora, non solum in operatione qua movent corpora, sed etiam in hoc quod in seipsis cognoscitivae sunt, licet brutorum cognitio sit materialium tantum et materialiter....

St. Thomas placed the form of the magnet and its powers in the hierarchy of forms intermediate between 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 through its active and passive qualities, but inferior to the plant soul, that has the powers of growth from the "virtus coeli." This is similar to Galen's comparison of the magnet's powers to that of the nutritive powers of organic bodies.

In his commentary on Aristotle's _Physics_, St. Thomas explained how iron is moved to the magnet. It is moved by some quality imparted to the iron by the magnet.[25]

Illud ergo trahere dicitur, quod movet alterum ad seipsum. Movere autem aliquid secundum locum ad seipsum contingit tripliciter. Uno modo sicut finis movet; unde et finis dicitur trahere, secundum illud poetate: "trahit sua quemque voluptas": et hoc modo potest dici quod locus trahit id, quod naturaliter movetur ad locum. Alio modo potest dici aliquid trahere, quia movet illud ad seipsum alterando aliqualiter, ex qua alteratione contingit quod alteratum moveatur secundum locum: et hoc modo magnes dicitur trahere ferrum. Sicut enim generans movet gravia et levia, inquantum dat eis formarum per quam moventur ad locum, ita et magnes dat aliquam qualitatem ferro, per quam movetur ad ipsum. Et quod hoc sit verum patet ex tribus. Primo quidem quia magnes non trahit ferrum ex quacumque distantia, sed ex propinquo; si autem ferrum moveretur ad magnetem solum sicut ad finem, sicut grave ad suum locum, ex qualibet distantia tenderet ad ipsum. Secundo, quia, si magnes aliis perungatur, ferrum attrahere non potest; quasi aliis vim alterativam ipsius impedientibus, aut etiam in contrarium alterantibus. Tertio, quia ad hoc quod magnes attrahat ferrum, oportet prius ferrum liniri cum magnete, maxime si magnes sit parvus; quasi ex magnete aliquam virtutem ferrum accipiat ut ad eum moveatur. Sic igitur magnes attrahit ferrum non solum sicut finis, sed etiam sicut movens et alterans. Tertio modo dicitur aliquid attrahere, quia movet ad seipsum motu locali tantum. Et sic definitur hic tractio, prout unum corpus trahit alteram, ita quod trahens simul moveatur cum eo quod trahitur.