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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. Koyre 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 Koyre, _Etudes galileennes_, 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.

[Illustration: Figure 1.--WILLIAM GILBERT'S BOOK ON THE LOADSTONE,
TITLE PAGE OF THE FIRST EDITION, FROM A COPY IN THE LIBRARY OF
CONGRESS. (_Photo courtesy of the Library of Congress._)]

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, _Beitraege 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] Rene 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 <DW25> 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.

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 loadstone 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. Thus 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 alteration. Moreover the source of this
alteration in the iron is not the heavens but the loadstone.
Accordingly the loadstone could cause change in another substance
because it could influence the nature of the other substance.

    [22] St. Thomas Aquinas, _op. cit._ (footnote 19), vol 7,
    _Scriptum in quartum librum sententiarum magistri Petri
    Lombardi_, lib. 4, disq. 33 (De diversis coniugii legibus),
    art. 1 (Utrum habere plures uxores sit contra legem naturae),
    p. 168. The same statement occurs in one of his most mature
    works, _op. cit._ vol. 20, _Summa theologica_, pars 3
    (supplementum), quaestio 65 (De pluralitate uxorum in quinque
    articulos divisa), art. 1 (Utrum habere plures uxores sit
    contra legem naturae), p. 107.

    [23] St. Thomas Aquinas, _op. cit._ (footnote 19), vol. 8,
    _Quaestio unica: de spiritualibus creaturis_, art. 2 (Utrum
    substantia spiritualis possit uniri corpori), p. 404. See
    also vol. 9, _Summa contra gentiles_, lib. 3, cap. 92
    (Quomodo dicitur aliquis bene fortunatus, et quomodo
    adjuvatur <DW25> ex superioribus causis), p. 344; and vol. 17,
    _Opuscula, De operationibus occultis naturae ad queindam
    militem ultramontem_, pp. 213-214.

    [24] St. Thomas Aquinas, _op. cit._ (footnote 19), vol. 8,
    _Quaestio unica: de anima_, art. 1 (Utrum anima humana possit
    esse forma et hoc aliquid), p. 437. See also vol. 8,
    _Quaestio: De veritate_, quaestio 5 (De providentia), art. 10
    (Utrum humani actus a divina providentia gubernentur mediis
    corporibus coelestibus), p. 678.

    [25] St. Thomas Aquinas, _op. cit._