FORMULATION OF THE CONCEPT

Few dicta are more inextricably linked with the Middle Ages than the declaration that “nature abhors a vacuum.” Although the full significance of this famous principle would be described and explicated only in the fourteenth century, it had already emerged in the thirteenth, when expressions such as natura abhorret vacuum, horror vacui, and fuga vacui began to appear. The origin of the principle is, however, unknown. But already in the first half of the twelfth century, Adelard of Bath expressed the fundamental idea of nature's resistance to a vacuum. In denying that magic plays any role in the failure of water to pour out of the holes in the bottom of a clepsydra when the holes in the top are stopped up, Adelard explained this strange phenomenon in cosmic terms by observing that

As the place within which bodies could move and rest and the potential frame of the universe, empty space was a central theme in physical thought from Greek antiquity to the Scientific Revolution. Despite a great awakening interest in the history of science in this century, only a few significant studies have appeared to shape our understanding of earlier spatial conceptions. However much these works may differ from each other, they share one common feature: Medieval and early modern scholastic contributions are excluded from serious consideration, and in most cases mentioned not at all. Given the almost universally held assumption that Aristotelian scholastics had nothing to contribute, their omission caused no comment. Serious discussions on space were thought to have begun in the Renaissance with the likes of Nicholas of Cusa or Bernardino Telesio.

The historical realities, however, are quite otherwise. Scholastics did indeed play a significant role in the development of a concept of infinite space that would be acceptable to the majority of nonscholastics for whom the relationship between God and space was still a vital matter. Demonstration of this claim is a major objective of my study, which is divided in two major parts (the third being a conclusion). The first concerns the existence of intracosmic void, which was always conceived as if it were surrounded by the innermost surface of one or more material bodies.

Medieval concern for the various problems associated with the possibility of void space within the world was, as we have now seen, both extensive and intensive. This is hardly surprising when it is realized that every commentator on Aristotle's Physics had to confront a variety of arguments against the possible existence of empty space. With regard to the possibility that a vacuum might exist beyond the boundaries of the cosmos, the situation was quite different. For although, as will be seen, Aristotle had occasion in De caelo to reject extracosmic space, he considered the matter only briefly, and scholastic commentators on De caelo rarely used Aristotle's discussion as a point of departure for further speculation. In fact, brief discussions on extracosmic void were just as likely to turn up in commentaries on the Physics. Although Aristotle's arguments for the rejection of extracosmic void were to play a central role, the probable reason why the subject of extracosmic void did not become a regularly discussed theme in the Aristotelian commentary literature is the theological nature of the problem as it emerged in the Middle Ages during the thirteenth century. Although the historical roots of the concept of extracosmic void were both secular and theological, speculation about it became significant in the late Middle Ages only after it became enmeshed in theological debates about God's location, His absolute power, and the conditions that obtained before the creation.

ARISTOTLE'S REJECTION OF EXTRACOSMIC VOID AND THE REACTION IN GREEK ANTIQUITY

The idea of extracosmic void space reached the Latin West from a number of sources during the Middle Ages. As with so much else, it was Aristotle who conveyed the concept in the form that would be most widely known and that would be central to all subsequent discussion. In the course of rejecting the existence of a plurality of worlds in De caelo, Aristotle declared categorically that “neither place, nor void, nor time” can exist “outside the heaven.” He had earlier argued that no bodily mass could come into being beyond the heavens, or outermost circumference of the universe, and inferred from this that neither place nor vacuum could exist there because “in every place a body can be present” (no body, therefore no place) and because “void is said to be that in which the presence of body, though not actual, is possible” (no possibility of body, therefore no vacuum). Aristotle concluded that absolutely nothing existed beyond the universe, a nothing that was best characterized as a privation. His denial of extracosmic existence to place, void, time, and body was frequently repeated. Special reliance was placed upon the necessary connection between body and void. By definition, vacuum was conceived as a place devoid of body but capable of receiving it.

THE PROBLEM OF INSTANTANEOUS MOTION

Among Aristotle's arguments denying the possibility of motion in a vacuum (see Chapter 1), none was viewed as more fundamental than the deduction that such motions would be instantaneous. As Aristotle expressed it, the speeds of bodies moving in a void would be “beyond any ratio”; or, to put it another way, a body would occupy the termini of its motion, and all intervening points, simultaneously. Before describing the subsequent history of this powerful argument, it will be well to take note of a paradoxical feature that was implicit in many discussions of it. Did the assumption of instantaneous motion in a vacuum categorize one as a proponent of motion in a vacuum, even though that motion is instantaneous or of infinite velocity? Or rather, did the assumption of instantaneous motion imply that its proponent actually denied motion in a vacuum because the very concept of instantaneous motion is absurd and impossible? One can scarcely doubt that Aristotle was of the latter opinion. For him, the consequence that motion in a vacuum would be instantaneous was equivalent to a denial of motion. Thus instantaneous motion in a vacuum is no motion at all. But already in the thirteenth century, Roger Bacon distinguished between those motions in a void that were instantaneous (and presumably nontemporal) and those that were successive (and therefore finite and temporal).

With perhaps a few minor exceptions, there was little serious discussion of the possibility of extracosmic void prior to the Condemnation of 1277. When the problem did arise, Aristotle's rejection was usually adopted with little elaboration, as in the anonymous Liber sex principiorum, falsely ascribed to Gilbertus Porretanus; in Johannes de Sacrobosco's Sphere; and in Robert Grosseteste's Commentary on the Physics. Even Thomas Aquinas found little occasion to discuss the possibility seriously, perhaps because he thought extracosmic void an untenable suggestion.

After 1277, however, the situation altered dramatically and the possibility of the existence of extracosmic space came to be discussed in two interrelated, though distinguishable, contexts. In the first context, the primary concern was with the possible existence of void space independent of God but assumed to have been created by Him before, during, or after the creation of the world. The possibility that God could create finite vacua at will was regularly conceded after 1277, though His ability to make an infinite vacuum was, as will be seen, seriously questioned. In the second context, extracosmic void space was not assumed independent of God but was conceived to be in some sense associated, as a property or attribute, with God's omnipresent immensity. Although not all discussions of extracosmic void can be fitted neatly into one or the other of these two contexts – Jean de Ripa's treatment of the subject, for example, seemed to fall into both – it is convenient to consider them separately.

The concept of space that will be of primary concern in this volume is one in which space was regarded as something separate from material body. With a few rare exceptions, that separate space was associated with a vacuum that was assumed to exist either within the confines of a finite, spherical universe, as described by Aristotle, or beyond the bounds of that universe, extending infinitely in every direction.

Although our study focuses on the period between the thirteenth and seventeenth centuries in Western Europe and, except for the last two chapters, is largely confined to the Aristotelian scholastic tradition, the central role of vacuum in the history of spatial theories was firmly established in the fifth century B.C., when Greek atomists designated void as a “nonbeing” that was as real as the hard, impenetrable, and eternal atoms that randomly moved and collided through its infinite extent. The atomist identification of real, albeit empty, space with “nothing” guaranteed that the history of spatial concepts would, from its inception, be rooted in paradox and enigma. Described and defined as nothing by the terms that came to represent it – kenon in Greek; inane, vacuum, and nihil in Latin – the void was from the outset, and almost inevitably, subjected to a double entendre. Was it an unintelligible, total privation incapable of existence – a true “nothing”?

Throughout the Middle Ages, the three-dimensional void space rejected by Aristotle as a candidate for place was regularly described as the “common” or “vulgar” opinion. Not only did Aristotle himself suggest this in the Physics, but ironically, the characterization of three-dimensional void space as common or vulgar was invoked in the Middle Ages in order to save Aristotle from the charge that he himself had advocated the rejected opinion. For it was generally acknowledged that in the Categories, or Predicamenta, as it was known in the Middle Ages, Aristotle had actually assigned the properties of tridimensionality and divisibility to place and body. According to one scholastic interpretation, Aristotle was believed to have declared in the Predicamenta that “as are the dimensions of a body so are the dimensions of its place and conversely; and that the parts of a body are joined (copulantur) to the parts of its place.” No exegesis, however subtle, could explicate the passage in the Predicamenta as suggestive of place as a two-dimensional surface, the position upheld by Aristotle in the Physics and known to be his true opinion. The dilemma was resolved by appeal to Averroes, who, in his Commentary on the Metaphysics, explained that in the Predicamenta Aristotle had frequently described common, or vulgar, opinions, whereas he sought to determine the truth in other parts of philosophy.

JOHN MAJOR AS A POSSIBLE LINK BETWEEN MEDIEVAL AND EARLY MODERN SCHOLASTICS

Although we have now seen that numerous late medieval authors had occasion to express an opinion on extracosmic void, few considered it within the theological context developed in the last chapter. This situation changed dramatically during the sixteenth century, when the relationship of God and a possible infinite void space came to be discussed at great length by numerous scholastic authors of major and minor significance. That the problem was a legacy of the late Middle Ages can scarcely be doubted. And yet the names of Bradwardine, De Ripa, and Oresme, who accepted the possibility or actuality of an infinite void space associated with God's immensity, go unmentioned in the great debates that developed in the sixteenth and seventeenth centuries. Despite the publication of Bradwardine's De causa Dei by Henry Savile in 1618, it played no apparent role in the sixteenth century, and no citation of it in the seventeenth has yet come to light. But the ideas that Bradwardine, De Ripa, and Oresme expressed are much in evidence and may plausibly be assumed to form the ultimate basis for the elaborate and detailed discussions of the later period. But by whom were their ideas transmitted?

Aristotle's denial of the existence of a separate void space must form the point of departure of any consideration of the history of spatial concepts from the Middle Ages to the Scientific Revolution. As an entity possessed of dimensions, such a space would have been equivalent to body and therefore unable to receive material bodies. But even if void space existed, finite and successive motion in it would be impossible, as Aristotle's numerous arguments had demonstrated. Although medieval and early modern scholastics would follow Aristotle and reject the actual existence of intracosmic void, they were nevertheless prepared to consider the behavior of bodies in hypothetical extended vacua. From such conjectures and speculations, many in the Middle Ages would conclude that if extended vacua could exist, motion in them would indeed be finite and successive, a conclusion derived from the widely accepted argument known as the distantia terminorum. On the basis of the Aristotelian assumption that extended void is like a body and therefore divisible into parts, the distantia terminorum argument provided a rationale and justification for finite and successive motion by demonstrating that successive parts of that vacuum could be traversed only sequentially and therefore of necessity in a finite period, however small. Widely accepted as kinematically sound, the distantia terminorum argument also demanded a causal explanation, which proved difficult to provide.

In arriving at his definition of the place of a body as “the boundary [or inner surface] of the containing body at which it is in contact with the contained body,” Aristotle had occasion to reject three other possibilities, namely that place is (1) shape or form; (2) the matter of a body; and (3) the extension between the bounding surfaces of a containing body. The last of these represented the concept that place is a three-dimensional void space. By defining void as “place bereft of body,” it was easy to infer that a void place is something distinct from the bodies that occupy it. Indeed because most people believed “that everything is somewhere and in place,” it would seem that, like Hesiod's chaos, place, or space, would necessarily precede the things that must move and rest in it. “If this is its nature,” Aristotle declared, “the potency of place must be a marvellous thing, and take precedence of all other things. For that without which nothing else can exist, while it can exist without the others, must needs be first; for place does not pass out of existence when the things in it are annihilated.”

If Hesiod and the atomists could find justification for the existence of such a separate, empty space, Aristotle found it an unintelligible conception from which only absurdities and impossibilities followed. For if place or space were three-dimensional, it would be a body.

THE IMPACT OF THE NEW GREEK TREATISES

As nonscholastic interpretations and approaches to nature gained adherents during the sixteenth and seventeenth centuries, many of whom would be among the leading scientific and philosophical thinkers of the period, a common attitude toward scholastic authors and their works developed. When not characterized by downright hostility and contempt, this attitude is best described as indifference. With regard to discussions of space and vacuum generally and infinite space in particular, indifference was usually manifested by silence. Except for occasional mention of an opinion or attitude of the “schools” or “schoolmen,” and even one specific and respectful citation of scholastic sources, nonscholastic authors chose to document and support their varied arguments about space, whether associated with God or not, with ancient Greek authors (Plato, Proclus, Epicurus, the Stoics, Hero, Simplicius, Plutarch, Philoponus, Hermes Trismegistus, etc.), the Church Fathers, Cabbalists, and nonscholastic predecessors and contemporaries. Silence about, or contempt for, the large and detailed scholastic literature on infinite space does not and cannot legitimize the inference that scholastic ideas about space and God played no role in shaping nonscholastic interpretations and opinions. It only makes the determination of such influences difficult to demonstrate and document. As the previous chapters have shown, the problem of infinite space and its relationship to the deity had engaged the attention of scholastic authors since the fourteenth century.

An institutional anniversary provides the occasion to stand back from the transient pre-occupations of administration, teaching and research, and look at the tradition in which the particular institution operates. In my own case, several factors have coincided to make the process especially congenial. The first, and most important, is very personal, and concerns my attitude to history. Twenty years ago, the suggestion that I should write a book on the history of the Botanic Garden, or of Cambridge botany, would have worried and even depressed me: now I find the opportunity richly rewarding. I can only report this change of heart without comment.

A second factor is the product of my career as Curator of the Herbarium and Lecturer in the Botany School, from which I was appointed in 1973 as Director of the Garden. This translation from a professional career in scientific botany in the main University Department to my present post enables me to appreciate the separate and combined elements in two interestingly different traditions, and stimulates me to ask how the differences came about. To some extent, this book is a product of such questioning.

The third of the factors encouraging me to write this little book concerns the nature and size of the University Botanic Garden itself. An institution occupying under 40 acres and employing fewer than 40 people is a comprehensible whole, in which it is possible to feel personal links and loyalties and to understand the nature and strength of tradition.