Charles Schmitt-Experimental Evidence for and Against Void

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Experimental Evidence for

and against a Void: The

Sixteenth-Century Arguments

By Charles B. Schmitt*

I. INTRODUCTION

ONE OF THE CHIEF identifiable characteristics of the period which

we call the Renaissance is that philosophical thought gradually but

steadily rejected Aristotle as the dominant authority. The Stagirite's teach-

ings regarding logic, metaphysics, and psychology were all seriously and

fundamentally questioned during the fourteenth and fifteenth centuries. In

the course of the sixteenth century there emerged a strong critical tendency

which directed its attention more toward Aristotle's natural philosophy.

Among the thinkers of this century who criticized Aristotle from one or

another viewpoint concerning his doctrines of natural philosophy were

Gianfrancesco Pico, Julius Caesar Scaliger, Petrus Ramus, Bernardino Te-

lesio, Francesco Patrizi, Giambattista Benedetti, Giordano Bruno, and the

young Galileo Galilei. In all of these writers we find a deep-seated antipathy

to the Peripatetic world view.

Included in nearly all sixteenth-century critiques of Aristotle is some dis-

cussion of whether a void or empty space exists or could exist in nature with-

out supernatural intervention. Since the Aristotelian dictum nature abhors

a vacuum turned out to be one of his most questionable pronouncements

and one which seems to have been experimentally refuted in the seventeenth

century, it may be fruitful to once more consider the background of these

important experiments.1

In my opinion we can distinguish at least four different ways in which the

1 Of what has been written previously see

University of Leeds. A preliminary draft especially Pierre Duhem, Systeme du monde

of this paper was read before the History of (Paris: Hermann, 1913-1959), esp. Vol. VIII,

Science Society at San Francisco on 28 Dec. 1965. pp. 121-168; Cornelis de Waard, L'experience

The research necessary for the paper was car- barometrique: ses antecedents et ses explica-

ried out in part through the aid of Grant No. tions (Thouars: Imprimerie Nouvelle, 1936);

3809, Penrose Fund, American Philosophical W. E. K. Middleton, The History of the

Society. I would like to thank Professor Ernest Barometer (Baltimore: Johns Hopkins Press,

A. Moody for making a number of helpful sug- 1964); Middleton, Torricelli and the History

gestions in connection with its preparation. of the Barometer, Isis, 1963, 54:11-28.

3 52

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EVIDENCE FOR AND AGAINST A VOID

vacuum problem was discussed in the Middle Ages and Renaissance, namely

from theoretical, kinetic, theological, and experimental viewpoints.2 In this

paper I plan to deal with only the last of these and, even that one, only par-

tially. I shall discuss some of the experimental reasons which were com-

monly used in the course of the sixteenth century both for and against the

natural existence of a vacuum.

On the whole, we find that the Aristotelians showed greater interest in

vacuum experiments than did their opponents. This, of course, may seem

somewhat strange in view of the fact that the decisive blow against the vacuist

position was dealt in the middle of the seventeenth century largely through

experimental means. It is nevertheless the case that the most extensive dis-

cussions of experimental evidence for and against a vacuum in sixteenth-

century writings are to be found in the context of commentaries on Aristotle's

Physics and in the Quaestiones literature relating to the same work. It also

seems evident that the Aristotelian writers of the period are dependent in

large measure on the earlier commentaries and analyses of Aristotle's works.

Among the opponents of the Aristotelian position on the vacuum question

we find only two-Telesio and Patrizi-who discuss the experimental aspect

of the issue in a relatively detailed way. The fact that these two writers have

some rather unusual things to say on the subject gives them a particular

importance which should become apparent as we proceed.

Let us now compare the arguments advanced in favor of a vacuum by the

anti-Aristotelians with those used by the Aristotelians to show that a vacuum

cannot exist in nature. Among the questions which should be faced are the

following: (1) What relation, if any, is there between the sixteenth-century

discussions of vacuum experimentation and the experiments which played

such an important role in seventeenth-century discussions of the same sub-

ject? (2) Was the existence of a partial vacuum interpreted to mean that with

further evacuation a complete vacuum could be realized? (3) In what if any

way do the sixteenth-century discussions of vacuum experiments represent

an advance over like discussions of the thirteenth and fourteenth centuries?

II. THE COMPETING EXPERIMENTS

Duhem has pointed out that Aristotle and the Greek commentators did not

use experiment to demonstrate the impossibility of a void.3 This is not to

say that empirical and experimental arguments were not adduced in antiquity

2 1 plan to treat these viewpoints in greater even a vacuist like John Philoponus cites the

detail elsewhere. For further information see clepsydra argument only to show that air is not

Charles B. Schmitt, Changing Conceptions of weightless. See his In Aristotelis physicorum

Vacuum: 1500-1650, to appear in Proceedings libros commentaria, ed. H. Vitelli, Commen-

of the XI International Congress of the History taria in Aristotelem Graeca, Vol. XVII (Berlin:

of Science, Warsaw-Cracow, 24-31 August G. Reimeri, 1888), pp. 608, 612-613. I use the

1965. term experiment in a very general way in this

3 Duhem, op. cit., Vol. VIII, p. 123. Duhem paper to mean roughly an observation or an

admits (ibid., p. 125) that Aristotle and Simpli- experience of phenomena, either natural or

cius cited the clepsydra as showing that air has artificial and in no way do I mean to imply

weight. His assessment seems to be correct, for that the thinkers approached, other than in a

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CHARLES B. SCHMITT

in its favor, for we have the preface to Hero's Pneumatica4 to show that they

were. It remained, however, for the medievals to attempt systematically to

apply experiential evidence to resolve the questions raised by Aristotle in

the Physics. This they did (1) by developing various empirical arguments

against a vacuum actually existing in nature and (2) by refuting those argu-

ments which were meant to show that there are vacua in nature. Since the

thinkers of the Latin Middle Ages seem to have argued almost without excep-

tion that a vacuum cannot be produced in nature by anything less than a

supernatural power, the experimental evidence which they use ultimately

either supports the Aristotelian position or proves to be inadequate to demon-

strate the actuality of a vacuum ever existing secundum naturam. In other

words, all experimental evidence with regard to the vacuum problem either

acts as a positive support for the Aristotelian position or is inadequate to

refute it.5

In attempting to analyze the function which experiment played in six-

teenth-century discussions of the vacuum problem, we find that a new factor

enters the picture which had been absent in the medieval discussions. For

the first time since antiquity, it seems, there emerges a group of Western

thinkers who seriously entertain the possibility that either (1) there is a

naturally existing vacuum or (2) a void can be produced by purely natural

means. We can, therefore, study and directly compare the experimental evi-

dence adduced by the protagonists on both sides of the controversy. This

cannot be done in the case of the medieval discussions, for although many

experimental arguments were presented in favor of a vacuist position, they

seem always to have been refuted by counterarguments. Consequently, the

pro-vacuum arguments often appear to be merely the straw men later to be

demolished which fill out the contra section of a Scholastic question. In the

sixteenth century, however, we find flesh-and-blood defenders of a vacuist

position. These thinkers are quite willing to present, with all of the force

and vigor at their disposal, experimental evidence which they feel clearly

shows that the Aristotelian position is mistaken.

In general, the sixteenth-century discussions of vacuum experiments reveal

a rather confused situation which must be analyzed with great care. We find

very rudimentary way, the notion of experi-

ment which evolved in classical physics. The

precise meaning of experience and experi-

ment as they were used in the 16th century

is a matter of crucial importance for the entire

interpretation of Renaissance philosophy and

science. There has thus far been no detailed

and systematic investigation of this question

to the best of my knowledge. I plan to discuss

the matter further in a forthcoming paper to

be entitled Experiment and Experience: A

Comparison of Zabarella's View with that Ex-

pressed in Galileo's De motu.

4 Heronis Alexandrini opera quae supersunt

omnia, ed. Wilhelm Schmidt (Leipzig: Teub-

ner, 1899), Vol. I, pp. 2-28.

5 I do not preclude the possibility that there

may have been an isolated Latin who would

have argued that a vacuum could be naturally

produced or naturally exists. The only Latin

thinker, to the best of my knowledge, who held

such a position is Nicholas of Autrecourt. See

J. Reginald O'Donnell, Nicholas of Autre-

court, Mediaeval Studies, 1939, 1:216-222. In

the medieval Arabic and Hebrew traditions the

situation seems to have been different. See

Salomon Pines, Beitrdge zur islamischen Ato-

menlehre (Berlin: Heine, 1936); Franz Rosen-

thal, Das Fortleben der Antike im Islam (Zu-

rich/Stuttgart: Artemis Verlag, 1965), pp. 236-

242; and Harry A. Wolfson, Crescas' Critique of

Aristotle (Cambridge, Mass.: Harvard Univ.

Press, 1929), esp. pp. 54-62, 181-189, 398-422.

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the Aristotelians and anti-Aristotelians repeating the medieval arguments, but

more important than this, we often find them citing the same arguments,

ostensibly based on direct observation and experiment, to demonstrate the

validity of their two diametrically opposed theses. That is to say: the same

experiment is used to show that in nature there is a vacuum and that

there is not a vacuum. Let us now investigate several of these arguments in

some detail.

A. The Bellows

We first consider the case of the bellows and related phenomena. Argu-

ments based on the operation of this widely known device are among the

most common found in medieval and Renaissance discussions of the void. A

typical sixteenth-century statement of the argument to support the Scholastic

position is the following taken from the commentary on the Physics written

by the Jesuits at the University of Coimbra:

But experience as well as reason persuades the authority of philosophy that

a vacuum is not to be granted in the nature of things. Experience, because,

for example, the sides of the bellows, if they are drawn together, can be

separated by no force, unless the orifice, by which air might enter to fill the

interior space, is open.6

We find a more detailed description of the same phenomenon with certain

added embellishments in Franciscus Toletus' commentary on the Physics:

If the bellows are taken, completely folded up, and the bellows' orifice were

inserted into a jar, well closed on all sides, so that air could not enter, and

the sides of the bellows were raised, then certainly there would necessarily

be a vacuum within the bellows, for there would not be a place from which

the air might enter; since if the air in the jar would enter into the bellows,

it would be necessary that the jar be left void, for there would be no place

where air might enter into the jar.

. . It must be said that in this case the sides of the bellows would not

be raised, for if much force were applied, they would without doubt be

broken, because if they would not break they could not be separated.7

These are largely the traditional arguments which had been used during

the Middle Ages against the possibility of the natural occurrence of a void.

They were certainly known to all of the natural philosophers of the period we

are discussing. What, we might ask, was the reaction of the anti-Aristotelians

to these arguments? As we have said, the approach of these thinkers to the

vacuum question is not generally an experimental one. Nevertheless, they do

pay some attention to this type of experimental problem. Consequently,

Bernardino Telesio, one of the century's most incisive opponents of Peri-

6 Commentariorum Collegii Conimbricensis

Societatis Iesu in octo libros physicorum Aris- 7 Francisci Toleti . . . commentaria . . . in

totelis Stagiritae secunda pars (Lyon, 1602), col. octo libros Aristotelis de physica ausculta-

90. For a similar statement see Domingo de Soto, tione . . . (Lyon, 1580), pp. 451, 453. Cf. Giro-

Super octo libros physicorum Aristotelis quaes- lamo Cardano, De subtilitate, I, in Opera omnia

tiones (Salamanca, 1582) fol. 65vb. (Lyon, 1663), III, 359b.

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CHARLES B. SCHMITT

patetic philosophy, admits that it is true that if one attempts to open a bellows

with the orifice blocked, something will break, but only under the condition

that the material which joins the two sides is loose and thin. If it were

thick and heavy, it could not be broken.8 A similar experiment which does

not involve precisely a bellows, but illustrates the same thing, is considered

by Francesco Patrizi:

If a pouch full of water is squeezed, the water will flow out and the pouch will

remain compressed. Then let its mouth, through which the water has flowed,

be bound as tightly as possible. This done, let the pouch be stretched by

the hands; it will follow the hands, and thus the space inside will become

large, and since neither air, water, nor any other body entered it through the

bound mouth, who will henceforth doubt that that entire space is empty of

all body 9

We have here the rather puzzling situation in which the same type of

experiential evidence is used in defense of both of the opposing positions in

the controversy. The Aristotelians argue that a bellows with a restricted ori-

fice will break rather than allow an empty space to be opened up. Patrizi

seems to try to meet the argument head on by saying that a collapsible con-

tainer can indeed be made to house a space empty of all body. It is, however,

somewhat difficult to see precisely how he could accomplish this, if indeed

the container be completely empty and leak free. From Patrizi's description,

the device which he has in mind seems to be similar to the normal wineskin;

and to manually separate the sides of a collapsed wineskin whose opening

is blocked is certainly no easy task.

The arguments of the Aristotelians, on the other hand, seem to have

greater force (if we for a moment consider at face value the experimental

evidence in the arguments), for if one does apply force to separate the sides

of the normal bellows under the conditions stated, there will usually occur

a break at the weakest point or a leak. The realization of this fact probably

led Telesio to his rather ingenious solution. He argues that if we take ade-

quate precautions to make all parts of the bellows strong enough and if

we can apply a powerful enough force, the sides will actually be separated

and a void space created between them. Telesio seems to be arguing here, as

we shall see he does elsewhere, that in carrying out certain experiments special

apparatus must be designed or special conditions for the experiment must

be established. As he sees it, the Scholastic argument fails to become decisive

precisely because its adherents had not gone beyond a few very simple cases

in which the experiment is applicable. If the experiment is extended to take

in a variety of different conditions and provisions are made to construct a

8 Bernardini Telesii De rerum natura, ed. Igitur . . . in folle spatium vacuum fieri

V. Spampanato (Modena: Formiggini, 1910- fatendum est.

1923), Vol. I, p 88: 9 Francesco Patrizi, Nova de universis phi-

Follem itidem si comprimas et occludas, ut losophia libris quinquaginta comprehensa . . .

nullus illabenti aeri aditus pateat, tum ele- (Venice, 1593), Pt. II, fol. 63c. The English

vas expandasque, si pellis laxa gracilisque translation is taken from Benjamin Brickman,

sit, dirumpi earn videas; minime vero, si Francesco Patrizi on Physical Space, Journal

pellis crassa, densa et frangi inepta sit. of the History of Ideas, 1943, 4:234.

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bellows strong enough to withstand these conditions, the results obtained

will be different.

B. Freezing Water in a Closed Container

A second class of widely discussed experiments considers the result of

freezing a filled, closed container of water. Typical of the solutions offered

to this traditional problem is that of Toletus:

A very strong jar full of hot water is taken, and let it be well closed; then let

it be put in a very cold place. Either the water will freeze or it will not. If

not, it seems absurd since the natural agent should necessarily perform its

action. If it does freeze, then the water will occupy a small place because of

its condensation and the rest of the jar will remain void.

. I admit that the water should become cold and should freeze, never-

theless this could not be without the evaporation of subtle vapors, which

would fill the place left by the water.10

It will be noted here, as in what follows, that the assumption that water will

decrease in volume upon freezing seems to have been universally held among

the writers we are discussing.

Using a somewhat different line of reasoning to reach the same conclusion,

the Coimbra commentators argue: The water contained in the jar either

does not solidify because nature prevents the solidification, which it prefers

to the risk of a vacuum; or, if it does solidify, the jar itself is broken. 11

This mode of argument raises an additional problem, however. Certainly the

normal ceramic or glass jar might be expected to break under the circum-

stances, but what would happen were we to use a very strong (i.e., unbreak-

able ) container for the experiment? Are nature's laws invariable enough

that we might expect even a metal container to be broken in preference to

the law of fuga vacui? This question is faced squarely by the Spanish Domini-

can Domingo de Soto. After saying, as Toletus does, that there would have

to be an evaporation of some sort before the freezing would take place, the

Dominican continues:

But if you press the matter further. Let it be granted for example, that there

is a perfectly spherical iron container, completely uniform everywhere in

thickness and strength. This could be done either naturally or supernaturally.

Having no orifice, but nevertheless full of water and surrounded by the cold,

it could freeze. It is asked then, where it might break, lest a vacuum be

granted. It is answered that, in so far as I judge that water is heavy, it will

freeze in the lower part toward the earth; for this reason it will break at the

higher point, lest a vacuum be granted there.12

Thus, even if we have a strong iron container, it will break rather than

allow a vacuum. It seems as though by this time the Aristotelian horror

vacui had become one of the dominant laws of nature; it was held that all

l0 Toletus, op. cit., pp. 451, 453.

11 Collegium Conimbricense, op. cit., cols.

94-95.

12 De Soto, op. cit., fol. 66ra.

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CHARLES B. SCHMITT

sorts of rather unusual phenomena would take place rather than allow an

empty space to come about.

An opposing position was again taken by those two eminent anti-Aristo-

telians Telesio and Patrizi. Both argue that when the closed container is

put out into the cold the water will freeze, it will occupy less space, and

part of the container will become void of any body.13 Neither seems to be

particularly concerned about the problem of whether the container will break

or not, which apparently obsessed the Scholastics. It is to be supposed that

they could solve this problem in the same way as a similar problem was solved

in the bellows experiment, that is by using a container strong enough to

withstand any normal force which would be encountered. To the Scholastics'

contention that upon freezing, the water will give up vapors which will pre-

vent the formation of a void, Telesio argues that, on the contrary, when the

water contracts and freezes, you will find by experience that the vapors

and smoke will have become condensed into the water. 14 Telesio's argu-

ment is certainly more in accord with modern views regarding the reduction

of the vapor pressure of a liquid upon cooling and the significantly lower

vapor pressures of solid substances than of the corresponding liquid form.

One cannot help but think that it was also obvious to the observant indi-

vidual of the sixteenth century. In fact, such a thing is very definitely im-

plied, if not precisely spelled out, in Aristotle's theory of the transformation

of elements as found in the De generatione et corruptione. However, the

very fact that both sides in this controversy, which was ostensibly based on

firsthand experience, failed so miserably to recognize the fact that water

does not decrease in volume upon freezing, but increases, is itself of sig-

nificance. This seems to indicate that much of the apparent emphasis on

experience found in sixteenth-century writers consists in merely repeating

the experimenta of earlier treatises.

Consequently, what is in actuality a meaningful question and one which

gives us no a priori reason for not admitting an experimental approach turns

out to be a hopelessly confused mass of invalid arguments. The common

premise held by both sides (that water contracts upon freezing) proves to

be a false one and none of the participants in the debate seems to have made

any attempt either to validate or to invalidate this long-held assumption.

All of this tends to indicate that in large measure the evidence admitted into

the controversy was based upon thought experiments and the repetition

of traditional stories culled from a variety of sources, rather than upon

direct observation of the phenomena in question. Here we reach an aporia,

for we can find no good reason to choose, considering only the evidence

given, either the solution of the Aristotelians or that of their opponents.

13 Telesio, op. cit., Vol. I, pp. 87-88; Patrizi, dique occludas, ut aer nullus prorsus subire

op. cit., fol. 63va. id queat, tum vehementi id exponas frigori,

manifeste spatium vacuum in eo fieri intue-

14 Telesio, op. cit., Vol. I, pp. 87-88: bere; nam aquam in glaciem et minorem

Quin si ens quippiam crassioribus vaporibus contractam in molem, vapores fumumque

crassioreve fumo aut aqua repleas ac un- in aquam conspissatum experieris.

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Both are rendered ineffective by their common false premise that water con-

tracts upon freezing.

C. The Clepsydra

Discussions involving the operation of the clepsydra, or water clock, go

back to Aristotle himself, although he used the device to show that air has

weight rather than to demonstrate the impossibility of a void.15 Later the

clepsydra experiment was used in a more positive way to show that a vacuurr

cannot exist in nature.16 Throughout the sixteenth century this argument

remained one of the stock empirical weapons used by the Peripatetics to

substantiate their position. The Aristotelian argument is clearly summarized

by Domingo de Soto:

In the first place is the experiment of the clepsydra full of water, which lets

out no water from below while the upper orifice is blocked, lest a vacuum

should result; although when it is half full, it lets out some water, because

the air (since there might easily be rarefaction of it) rarefies in the upper

part 17

Philip Melanchthon frames it in very similar terms, emphasizing that the

water hangs, as it were, lest there be a discontinuity in nature:

There is an evident sign that there may not be a vacuum, nor may such a

thing be possible. A vacuum would produce discontinuous bodies. ... In

the clepsydra nothing trickles down if the upper opening is blocked, since

air does not enter from above. Consequently, the water hangs [pendet], lest, if

it were to leave [the clepsydra], a vacuum would result. However, the rule

of motion of heavy bodies is not changed without cause. But this cause is

evident: that nature avoids the discontinuity of bodies.18

Both of these writers, as well as many others we have not mentioned, repeat

the traditional Scholastic arguments. There is no great difference between

these sixteenth-century versions and those of the thirteenth-century theo-

logians and natural philosophers on this point, although it might be noted

that Melanchthon, immediately after the passage cited above, quotes directly

from Lucretius' De rerum natura to give an opposing position on the

vacuum question. This one rarely finds before the sixteenth century.19

15 Physics 213a25-213a27. For a more detailed

discussion of the clepsydra see pseudo-Aristotle,

Problemata XVI, 8, 914b9-915a25. See also

Hugh Last, Empedokles and His Klepsydra

Again, Classical Quarterly, 1924, 18:169-173,

and D. J. Furley, Empedocles and the Clep-

sydra, Journal of Hellenic Studies, 1957,

77:31-34.

16 See especially Duhem, op. cit., Vol. VIII,

pp. 130-168 passim.

17 Soto, op. cit. fol. 65vb. An alternative type

of demonstration, very common in the litera-

ture, is the following: If the upper orifice is

closed and the lower perforated portion of the

clepsydra is dipped into water, the water will

not enter, for there is no way for the air to get

out. See, for example, Hieronymus Borrius,

De motu gravium et levium (Florence, 1576),

pp. 226-227; Toletus, op. cit., p. 431; Julius

Pacius, Aristotelis . . . naturalis ascultation's

libri VIII (Frankfurt, 1596), pp. 600-601.

18 Philip Melanchthon, Initia doctrinae

physicae, in Corpus reformatorum, ed. C. G.

Bretschneider, Vol. XIII (Halle, 1846), col. 368.

19The extent to which sixteenth-century

Aristotelians were themselves influenced by

non-Aristotelian and non-Scholastic sources in

general, and by Lucretius in particular, re-

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CHARLES B. SCHMITT

We again find Telesio and Patrizi rejecting the Scholastic analysis of the

question. Once more Telesio suggests an interesting modification of the

original experiment, which would, according to him, demonstrate the oppo-

site of what it was originally meant to show:

Furthermore, it is permitted that space, which might in an absolute sense

be filled with no body and for that reason empty [inane] and void [vacuum],

may be granted or seen in the clepsydra itself. For these reasons the Peri-

patetics have argued that a vacuum cannot be granted: since if the clepsydra's

orifice is closed so no air can enter it and thus if the water within flowed

out of the lower openings, the place of the upper water might be rendered

void, by no means whatever will it flow out, but indeed the water stands

over the lower openings themselves and holds itself back. Moreover, this is

seen in all containers which are constructed in the same way and are every-

where closed so no air is allowed to enter them. Indeed, if you would make

only one opening of the clepsydra a little wider and you would somehow

open the lower part of it, you would see that the fluid within would im-

mediately flow down out of the [enlarged] opening and from the lower part.

Furthermore, honey and any other fluids which are a little heavier, as well

as very fine but dense and heavy powder, flow out of the openings of the

clepsydra.20

Telesio here argues to the effect that the Scholastics had not considered the

experiment in question carefully enough. He seems to agree with Melanch-

thon that water will hang in the clepsydra under the normal conditions

of the experiment. If the proper modifications are made, however, not only

quires further investigation. Julius Pacius cites

Lucretius often in reference to the vacuum

problem in op. cit., pp. 602-603, 605, 609-610,

633, 635. The De rerum natura was also used

in a striking way by Francesco Vimercato (Neal

W. Gilbert, Francesco Vimercato of Milan: A

Bio-bibliography, Studies in the Renaissance,

1965, 12:195) and Giulio Castellani (Charles B.

Schmitt, Giulio Castellani [1528-1586]: A Six-

teenth Century Opponent of Scepticism, Jour-

nal of the History of Philosophy, 1967, 5:15-39,

esp. pp. 36, 39). It is also interesting to note that

the avowedly anti-Aristotelian Gianfrancesco

Pico was cited as a source for arguments against

the Aristotelian view concerning the vacuum by

Collegium Conimbricense, op. cit., col. 90. See

Charles B. Schmitt, Who Read Gianfrancesco

Pico della Mirandola? Stud. Renaiss. 1964,

11:124-125.

20 Telesio, op. cit., Vol. I, p. 87:

Spatium porro, quod corpore nullo prorsus

repletum ac propterea inane vacuumque sit,

dari posse vel ipsis in clepsydris videre licet;

quae, quod si earum orificium ita occludatur,

ut aer nullus in eas subire queat, itaque si ex

infernis foraminibus inexistens aqua dela-

batur, superioris aquae locus vacuus fiat,

haudquaquam delabitur, sed vel quae fora-

minibus ipsis superstat, sustinet sese, vacu-

um dari non posse Peripateticis declarant.

In vasis praeterea omnibus, quae ita eaque

e re constructa et undique occlusa sunt, ut

nullus in ea ingressus aeri detur, hos spec-

tatur. Verum si unum tantum clepsydrarum

foramen paulo amplius effeceris et infernam

horum partem quidvis aperias, et ex illo

et ex hac inexsistentem fluorem statim deci-

dere videas. E clepsydrarum praeterea fora-

minibus, e quibus aqua non defluit, mel

fluoresque alii quivis paulo graviores et pul-

vis minutissimus at densus gravisque, decidit.

Patrizi's treatment of the issue is nearly the

same, op. cit., Pt. II, fols. 63rb-63va. A some-

what similar argument is the case of Cardano's

lamp, which became famous in the vacuum

discussions of the next centuries. This device,

consisting basically of an oil lamp, was said

to produce a vacuum when it begins to empty

because of the consumption of the oil. I plan

to write elsewhere on the long and interesting

history of this lamp as part of the vacuum con-

troversy. For Cardano's discussion of what he

calls the lucerna mirabilis, first treated in the

De subtilitate (first printing 1550), see his op.

cit., Vol. III, pp. 359-360. For an English trans-

lation and discussion of the relevant passage

see Leroy Thwing, Flickering Flames (Rutland,

Vt.: Tuttle, 1958), pp. 38-42.

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does the experiment fail to show the impossibility of a vacuum, but it seems

actually to indicate that there is more experimental evidence in favor of a

vacuum than against it.

D. Evacuation of a Vessel

One further bit of experimental evidence which was used in the sixteenth

century in favor of the vacuist position should now be discussed. Already

in antiquity Hero of Alexandria had argued that although not naturally

occurring, a continuous vacuum can be produced by drawing the air from

a container.21 This particular argument does not seem to have been dis-

cussed very extensively during the Middle Ages, although very similar ones-

for example, on the cupping glass-were quite common.22 One of the first

modern writers to make use of the ancient argument, as far as I have been

able to determine, was Adrian Turnebe in his De calore (completed before

1565). Here, though he touches on the vacuum problem only very briefly,

he argues, as Hero had, that there are inanitates quaedam interpositae in

nature. He then continues:

There is another certain emptiness, immense and extending widely, which

nature avoids, because of which it performs marvels, and propels heavy

body upward, which things it can nevertheless bring about. But, if you would

pierce through a glass ball and you would insert a small siphon through the

hole and you would carefully caulk around the hole, with your mouth you

could draw out the air which is inside and there would remain a great empti-

ness within. The proof of this would be the following: if before the air is let

in from the outside, you were to cover the siphon with your finger and you

were to turn it upside down in water, the liquid would enter when you

would remove your finger; and it would be drawn into the interior of the

ball.23

Francesco Patrizi cites essentially the same experiment, although in some-

what less detail. He does make one point which offers an important variation

of Turnebe's treatment. When describing the action of drawing out the air

from the sphere, he says: Let us draw out the air inside; we shall, without

doubt draw out a great deal; and thus there would necessarily remain much

of a vacuum. 24 Patrizi, therefore, realizes that only a partial vacuum can be

21 Hero, op. cit., Vol. I, pp. 8-10. For an Eng-

lish translation see The Pneumatics of Hero of

Alexandria, trans. J. G. Greenwood (London:

Taylor, Walton and Maberly, 1851), pp. 3-4.

22 See the texts of Duhem and De Waard

cited above in n. 1.

23 Adrianus Turnebus, De calore (Paris,

1600), fols. 15v-16r. The argument is repeated

in detail, including a direct quotation from

Turnebe, in Pierre Gassendi, Syntagma philoso-

phicumn, Sec. I, Bk. II, Ch. 4, in the Opera

omnia (Lyon, 1658), I, 198a.

24 Patrizi, op. cit., Pt. II, fol. 63rb: . . . in-

ternum aerem attrahamus, proculdubio mul-

tum extrahemus. Atque ita necessario vacui

multum relinquetur. Brickman (op. cit., p.

234) translates the last sentence as follows:

And so a large vacuum will necessarily be

left inside. This seems to me to be inaccurate.

The multum vacui seems to have the meaning

of a near vacuum or much of a vacuum

rather than a large vacuum. In the previous

sentence Patrizi has stated that a great deal

[multum] of air will be removed and not all

of the air. The distinction is, admittedly, a

rather minor one but in the present context

seems to be not unimportant. When Patrizi

speaks of large vacuum -as distinguished

from the small dispersed empty spaces we find

in the universe-he invariably seems to use the

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CHARLES B. SCHMITT

created by drawing the air out with the mouth. Turnebe, on the other hand,

gives every indication of actually believing that a complete vacuum can be

drawn. Regardless of this discrepancy between the two, both agree that the

experimental evidence is clearly in favor of a vacuist position.

III. ANALYSIS AND CONCLUSIONS

Let us now address ourselves to several questions of more general signifi-

cance. First, let us consider how the existence of a partial vacuum was in-

terpreted in the sixteenth century. Does the fact that we can draw a partial

vacuum (or, in more Scholastic language, produce a rarefied atmosphere)

indicate that a complete vacuum is possible or does it merely show that dif-

fering degrees of fullness are possible in a world which has no discon-

tinuity? The Scholastics generally held the position that the rarefaction and

condensation of matter can explain all of the phenomena which the positing

of a vacuum is meant to explain. However, with some Peripatetic thinkers

there appears to be a certain inconsistency. As we have seen, Toletus does

not seem to take the possibility of rarefaction into consideration in his

experiment of the bellows and the jar. This quite ingenious experiment,

which seems to offer a perfect instance for the rarefaction explanation, is

explained in rather disappointing and conventional terms. It stands in sharp

contrast with de Soto's contention regarding the clepsydra, where he argues

that when the device is only half full of water and the upper orifice is

blocked, some water will flow out, because the trapped air will increase in

volume to occupy the space left vacant by the outflowing water. There is,

consequently, some disagreement among the Aristotelians over just how the

rarefaction-condensation explanation will function. Patrizi, on the other

hand, who basically holds to a corpuscular theory very similar to Hero's (in

which there are naturally existing spatiola, void of all body, but no ingens

spatium vacuum), accepts this as evidence in behalf of the vacuum hypothe-

sis. There seems to be, therefore, a fundamental confusion-which goes back

to antiquity, we might add-as to what would constitute empirical evidence

for the actual existence of a vacuum. Ultimately, it seems to reduce to the

problem of whether rarefaction-condensation phenomena can adequately

be explained in terms of a full universe or whether a vacuum must be posited.

Thus, we find an Aristotelian (de Soto) citing the rarefaction of air as evidence

that there are no empty spaces in nature and an anti-Aristotelian (Patrizi)

citing it as evidence that there are.

From the Aristotelian point of view, although there is rarefaction and

condensation, the last bit of air, which marks the boundary between a rare-

fied but full space and an empty one, can never be extracted by natural

means. For the vacuist, the fact that some air can be extracted indicates that

term spatium inane. One should compare Gi- physicarum liber (Turin, 1585), p. 193. Here

ambattista Benedetti, Disputationes de quibus- Benedetti, one of the most distinguished 16th-

dam placitis Aristotelis, Ch. 34 in his Di- century defenders of the vacuist position, gives

versam speculationum mathematicarum et a rare allusion to experience.

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by the increased application of force more and more air can be removed

until finally the space will be empty. The disagreement arises over how the

same empirical data are to be interpreted and the crucial factor in the de-

cision seems to be the a priori theoretical construction which prompted the

experiment in the first place. Far from being decisive, the variously inter-

preted experiments merely reflect the already obvious position of their pro-

ponents. In a sense the results of the experiments have been determined

beforehand; given the conceptual framework in which they have been car-

ried out, they can give but a single result.

Secondly, how are the radically empirical arguments of Telesio and Patrizi

to be interpreted? As we have seen, both of these men present a series of

rather striking arguments which seem to go beyond the traditional empirical

discussions which we find among the Scholastics. Granted that the arguments

of these men show something of the inventiveness and ingenuity which must

be a stock resource of all good experimentalists, nevertheless there emerges

a further question to be considered. Do Telesio and Patrizi use the experi-

mental arguments in a positive way to establish the foundations of an em-

pirically based science or do they use them merely in a destructive way to

show that the Aristotelian arguments are not conclusive? Although both

make extensive use of empirical evidence in favor of their positions, their

general intent seems to have been to render the Aristotelian position inde-

terminate. As Patrizi at one place argues: Nothing is proved by them

[i.e., the ancients, who held that there is no vacuum] which the senses cannot

refute. 25 The implication is-and I think that a more careful examination

of Patrizi's general philosophical orientation will bear this out-that a sys-

tem of the physical world is basically a theoretical a priori construction, but

it must, at the same time, save the phenomena. There is always the phe-

nomenal world before us to act as a check for any system of natural philosophy,

and, for that reason, observation and experiment can reveal the weaknesses

of any system of natural philosophy. We can say, then, that experiment

does not appear to play a very important positive role in the formula-

tion of Patrizi's Neoplatonic philosophy. Experience and experiment are

more important in Telesio's philosophy of natura juxta propria principia,

but theoretical factors again generally seem to dominate.

Careful examination reveals that both Telesio and Patrizi adopt the stock

Aristotelian experiments meant to show that there cannot be a naturally

occurring vacuum in the physical world and they turn these against the

Peripatetics. The way in which the experimental arguments of Telesio and

Patrizi function bears a striking resemblance to the way in which the devel-

oping skeptical movement of the sixteenth century used arguments against

Aristotelian epistemology.26 The skeptic argued that the Aristotelian sense-

based theory of knowledge is valid only within a relatively narrow range

of boundary conditions and that further experiences drawn from outside

25 Patrizi, op. cit., Pt. II, fol. 63rb.

26 See my book, Gianfrancesco Pico (1469- phy (The Hague: Martinus Nijhoff, 1967), esp.

1533) and His Critique of Aristotelian Philoso- Ch. 4.

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CHARLES B. SCHMITT

this range render the Aristotelian theory unreliable at best. In general, both

Telesio and Patrizi say that the Scholastic experiments are valid as far as they

go, but when they are extended beyond the rather narrow limits envisioned

for them by their proponents, they not only fail to demonstrate what they

claim to, but indicate rather that the opposite is true. Once we have over-

come the technological problems of breaking bellows and cracking jars and

we have replaced the water of the clepsydra with heavier liquids, the vacuum-

less world picture is shattered. The Scholastic experimental arguments are

fine as far as they go, but to get a clearer and more accurate view of the world

we must extend them beyond their normal limits. It is only beyond the

realm of normal occurrence that we encounter the vacuum in a recog-

nizable form.27

Thirdly, let us consider what if any connection these experimental dis-

cussions have with the decisive experiments of the middle of the seventeenth

century. On the whole, it seems as though we do not find a great deal of

evidence to indicate that most of the writers we have been discussing were

really experimentalists themselves. There is a reliable tradition going back

to Telesio himself which attributes to him and to the followers of the phi-

losophia Telesiana an interest in experimentation.28 It seems clear, however,

that generally the writers who discuss the vacuum question do not really

go beyond the sum total of ancient and medieval knowledge on the subject.

In the writings which I have examined I have seen no discussion of the pos-

sible use of a suction pump to extract air from a vessel and thus create a

vacuum, although the suction pump was well known as a water-drawing

device in the sixteenth century.29 What seems evident, however, is that (1) cer-

tain ancient devices were reintroduced into the discussions, principally from

Hero's Pneumatica, (2) certain techniques known to the Arabs were either

reintroduced or rediscovered, and (3) some embellishments and modifica-

tions of the known experiments were suggested.

At any rate, almost all of the experiments which were utilized in the

vacuum discussions are rather primitive and by no stretch of the imagina-

27 A typically Aristotelian rejoinder to the

pro-vacuum arguments is that of the late 16th-

century Oxford professor John Case, who says:

Quintus locus [of the list of arguments he is

giving] est ab experientia, maxima, quod

omnia exempla quae ducuntur ad proban-

dum vacuum probe examinata inferant con-

trarium. Ut sunt illa de fistula explosa de

terrae motus causa, de clepsydra, de curcu-

bitula, de dolio cineribus pleno, non minus

tamen aquae recipiente quam si esset vacu-

um, de tabulis et follibus compressis et un-

dique obstructis. Sed haec omnia praetereo,

concludens nihil esse in rerum natura vac-

uum naturaliter: non negans tamen fieri

possit vi supernaturali et divina, quae nul-

lis mediis alligata potest in nihilum corpora

commutare efficere. (Ancilla philosophiae

seu epitome in octo libros physicorum Aris-

totelis [Oxford, 1599], p. 70; his italics.)

28 Antonio Persio, Liber novarum posi-

tionum (Venice, 1575), fol. 3v; Francis Bacon,

De principiis atque originibus secundum fabu-

las Cupidinis et coeli: sive Parmenidis et Tele-

sii et praecipue Democriti philosophia tractata

in fabula de Cupidine, in The Works of Fran-

cis Bacon, ed. James Spedding and Robert

Leslie Ellis (London: Longman, 1857-1874),

Vol. III, p. 115; Tommaso Cornelio, Progymnas-

mata physica (Venice, 1663), pp. 118-120; and

Raffaello Caverni, Storia del metodo sperimen-

tale in Italia (Florence: G. Civelli, 1891-1898),

Vol. I, pp. 435-436.

29 Sheldon Shapiro, The Origin of the Suc-

tion Pump, Technology and Culture, 1964,

5:566-574. I am indebted to Prof. Lynn T.

White for calling this paper to my attention.

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tion give anything like a definitive solution to the problem. In certain

ways they do point the way to the work of Torricelli, von Guericke, and

their followers, but we must categorically state that they in no way approxi-

mate them. We do find that the sixteenth-century discussions offer certain

hints which could lead to the seventeenth-century experiments. Telesio's

and Patrizi's suggestion that heavier liquids be used in experimental appa-

ratus to produce a vacuum bears some resemblance to the later use of mer-

cury in the barometric experiments.30 Again, the suggestion of Turnebe

and Patrizi regarding the evacuation of a sphere, joined to the widely dis-

cussed experiment of the impossibility of drawing apart two perfectly smooth

plates,31 points the way to von Guericke's experiment, but in no very defi-

nite way

Fourthly, the use of force and the attempt to extract from the physical

world that which it does not give up naturally (e.g., by extracting the air

from a sphere or by applying an extraordinary force to a specially prepared

bellows) indicates the road to more successful experimental procedures of

the succeeding centuries. It was progressively found that compelling na-

ture to do what it was not its nature to do, so to speak, often disclosed new

truths about the structure of the world. What the Scholastics interpreted to

be the puzzling and somewhat aberrant phenomena resulting from nature's

horror vacui, the more modern thinkers interpreted in a much more posi-

tive way. As Turnebe argued, the reluctance of nature to admit a void is

responsible for many marvels (miracula). The great popularity of the re-

introduced Pneumatica of Hero and the consequent development of the sci-

ence of pneumatics in the following centuries clearly indicate the fruits of

such an attitude.32

In conclusion to our rather limited investigation we can say that no major

experimental breakthrough was achieved in the sixteenth century. What is

significant is that Aristotelians and non-Aristotelians alike did confront tra-

ditional Scholastic arguments with newly discovered pro-vacuum sources

from antiquity such as Lucretius and Hero. Even if these ancients seemed

to make little impression on the Peripatetics (although they were known

30 It should be noted that certain medieval

Arabic thinkers had actually suggested the use

of mercury in such experiments. See Salomon

Pines, op. cit., esp. p. 80, n. 2.

31 The origin of this seems to be Lucretius,

De rerum natura I, lines 385-400. For its his-

tory see especially De Waard and Duhem as

cited in n. 1. Renaissance authors who discuss

it include de Soto, op. cit., fol. 66'a; Toletus,

op. cit., pp. 451, 453; and the Collegium Conim-

bricense, op. cit., cols. 89, 95. It is worth noting

that this seems to be the only experiential ar-

gument discussed by Galileo in the De motu

(1589-1590). See Le opere (Florence: G. Barbera,

1890-1909), Vol. I, pp. 394-395. This passage

is unfortunately not included in the recent

(partial) English translation by I. E. Drabkin

in Galileo Galilei on Motion and Mechanics

(Madison: Univ. Wisconsin Press, 1960). Per-

haps the most remarkable discussion of this,

especially with von Guericke's later experiment

in mind, is John Buridan, Subtilissime ques-

tiones super octo Physicorum libros (Paris,

1509), lib. IV, quaestio 7, fol. lxxiiiva, trans. into

French in Duhem, op. cit., Vol. VIII, pp. 126-

127

32 For Hero's influence in the Renaissance

see particularly Marie Boas, Hero's Pneumati-

ca: A Study of its Transmission and Influence,

Isis, 1949, 40:38-48, and Wilhelm Schmidt,

Heron von Alexandria im 17. Jahrhundert,

Abhandlungen zur Geschichte der Mathematik,

1898, 8:195-214.

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366 CHARLES B SCHMTT

and cited), they deeply influenced the new group of thinkers who were

openly hostile to the Aristotelian tradition. The experimental arguments in

favor of a vacuist position which were collected by the anti-Aristotelians

were a useful aid in the demolition of Aristotelian natural philosophy, but

they do not yet seem to have the importance which experiment will have in

the next century. The real development which took place within the group

of Renaissance pro-vacuum thinkers came from other roots. Most of the

evidence points to the fact that a vacuist position was considered to be ten-

able, not for reasons derived from experimental evidence, but for theoretical

reasons. The precise way in which the Renaissance scholars worked out a

coherent natural philosophy based on the vacuist presupposition must be

left for later study.

Documents

Charles Schmitt-Experimental Evidence for and Against Void