The coming to be of the worlds (cosmoi) is thus: (1) In severance from the infinite, many bodies, of all varieties of shape, move into a great void. (2) These, being assembled, create a single vortex, in which they collide, gyrate in every way, and are sorted like to like. (3) When because of the number they are no longer able to move round in equilibrium, then the fine ones move into the void outside, as if sifted, while the remainder stay together, become intertwined, join courses with each other, and bring about a first system, in the shape of a sphere.2
This cosmogony is said to proceed by “necessity” (anankē). Unlike Plato’s account in the Timaeus, however, this likely story includes no formative Demiurge, since “all varieties of shape” are present from the start. Also present are “the infinite” (again to apeiron, but now construed not just as boundless but as a positive being), “the great void,” and “many bodies.” These three crucial constituents of the universe—that is, of to pan—are uncreated and pregiven. From them, everything else ensues: regions of “like” things as well as the earth, the sun, the moon, the stars, and all other celestial bodies. The great void is the gathering area for those bodies that will form “a first system,” that system being our own cosmos.3 Other cosmoi will form in what Leucippus calls “the void outside.” Taken together, the great void and the void outside constitute the infinite void, and this all-encompassing void is differentially populated throughout by those compact indivisible material bodies called “atoms.”
The Atomist model entails a double infinity: the infinity of space and the infinity of the atoms that populate this space. Just as there can be no end to space in the universe, so there is no end to the number of atoms (and thus, as a corollary, to the number of worlds to which atomic combinations in turn give rise). As Epicurus (341–270 B.C.) put it, “The totality is infinite both in the quantity of atomic bodies and in spatial magnitude.”4 Instead of there being a fixed number of elements that make up material bodies—as Empedocles, Plato, and Aristotle all believed—the elements and bodies themselves are constituted from an unlimited number of atoms in diverse configurations. In fact, the two Atomist infinities here in question are closely related. On the one hand, an infinite number of atoms requires an infinite space in which to move; anything less would curtail their motions. (Also required is that this infinite space be essentially empty [kenon] or at least “porous” [manon].)5 On the other hand, an infinite space calls for an infinite number of bodies within it; otherwise, it would be merely the region for a few, or even many, bodies—but not for all possible bodies.6
The Atomists would agree with their archrival Parmenides that what is real is a plenum, adding only that what is real is plural and not singular. Since the void per se is empty of any material body, this means that the void in any of its three basic guises is necessarily “unreal” or “not real” (mē on). Yet the void exists (einai); indeed, as we have just seen, it must exist—exist as providing space—if the motion of the atoms is to be possible.7 As Aristotle is reported to have said concerning this double ontology: “The real exists not a whit more than the not real, empty space no less than body.”8 Atoms and the void, the ultimate constituents of the physical universe, both exist, although only one is real in any strict sense. Even if one has “being” (to on) and the other does not, they rejoin each other in the co-necessity of their common existence.
The ingrained wholism of Aristotle and Plato—their passionate desire for perfection, especially of a teleologically ordered sort—ends in a cosmographic picture of a closed and finite world with no further universe around it. In contrast, the Atomists seek, beyond minuscule atoms, that which is infinitely large—a universe of empty space. In the first case, an overriding concern with formal, rational order (an order that, if not found initially, has to be added to the precosmic matrix) eventuates in a world of discrete places, whereas in the second case a commitment to “saving the appearances” (and especially the appearances of particular perceptual objects) calls for a vision of an infinite spatial universe, populated by sporadic and endlessly varying combinations of atomic units—both universe and atoms sharing in a like imperceptibility.9 This difference of vision suggests that a radical departure from the primacy of place (first evident in Hesiod) occurred in the thought of the inaugural Atomists. For does not classical Atomism—a thousand years before Philoponus and two thousand years before Newton—plunge us into an unaccommodating, placeless space? Is there any place for place within the Atomistic void?
Democritus and Leucippus will not help us directly with these questions. Not only is the surviving evidence of their full-scale systems—called intriguingly the Great World System and the Little World System—extremely scanty, but these founding figures were not alive to answer Aristotle’s scathing critique of the void. Epicurus, who visited Athens at the time of Aristotle’s death in 322 B.C, was in a better position to answer this critique. This latter-day Atomist conceded to Aristotle that void is indeed placelike in certain basic respects. The concession was so striking that modern editors of Epicurus have been tempted to alter the standard Atomistic phrase “bodies and space” (sōmata kai chōra)” or “bodies and void” (sōmata kai kenon) to “bodies and place” (sōmata kai topos). However controversial this emendation has proven to be,10 the temptation is based on a substantive point. For the more Epicurus pondered Aristotle’s objections to the void as superfluous—superfluous precisely insofar as it duplicates what is already accomplished by place qua topos—the more he came to conceive of the void as locatory in nature. Void is that “in which” (hopou) atoms are located and that “through which” (di’ hou) they move.11 Precisely as such, it is what immediately situates any given atom. Does this mean that void surrounds the atoms it situates? One recent commentator draws our attention to
the striking similarity of Epicurean void, [regarded] as place, to Aristotle’s fluid, immediate place for moving objects. . . . [This void] is not a sort of extension that could be filled or not filled. It was simply an anaphēs phusis (“intangible substance”) surrounding the distinct, constantly moving atoms. . . . Void is accepted as the absence of body, but not, on that account, as the unoccupied part of an extended space. . . . For Epicurus, an atom did not strictly speaking occupy space; it was simply surrounded by the absence of body.12
If this characterization of Epicurus is right, then the mere existence of atoms does not, after all, entail the existence of open and empty, much less infinite, space. No such amplitude, no such vacuity, is required. To each atom there corresponds only a quite particular place in which it is located at any given moment. The fact that atoms are always moving means only that their places are continually changing. On this view atomic motion does not demand an abiding space that is “a continuous entity subsisting everywhere in the same degree and manner, both where bodies are and where they are not.”13 In short, we can retain the basic Atomist cosmologic that says “if there were no void, there would be no motion; but there is motion; therefore, there is void”14—without having to interpret such a void as continuous or empty, not to say infinite. The void is finite; it is the very place of each and every atom.
Epicurus rejoins Democritus and Leucippus by maintaining that a distinction is to be made between genuinely empty space or “void proper” (as we can call the original sense of void in the phrase “atoms and the void”) and what ought to be termed “vacuum,” that is, an empty part or portion of a compound entity constructed of atoms, for example, an empty stomach in a hungry human being. A vacuum is a form of nonbeing, even a nothing, but it exists within the compound—which in turn exists within the void proper. This is why we can speak intelligibly and not merely oxymoronically of a vacuum as a nonbeing that exists: here the ancient paradox is seen to apply to a more discrete entity. The vacuum exists precisely as a “space-filler” in the apt term of David Sedley, who remarks that a vacuum “occupies some parts of space just as effectively as body occupies others.”15 The Archytian axiom is undisturbed by this claim: for a vacuum exists just to the extent that it has a place in which to exist.16 Void proper—redescribed as “intangible substance” by Epicurus—is what provides such a place, its source as it were. Yet neither void nor vacuum is place in Aristotle’s strict sense of an always already occupied locus for fully formed material objects.17