SOURCE: “Democritus and the Atomic Theory: Materialism,” in The Philosophers of Greece, Thomas Y. Crowell Company, 1964, pp. 78-92.

[In the following excerpt, Brumbaugh summarizes Democritus's atomist philosophy, considers some criticisms of it, and relates it to the development of Greek mechanical devices.]

There is no chance, but all is from necessity.

leucipus

Nothing exists but atoms and the void.

democritus

Applying the logic developed in the Eleatic school by Parmenides and Zeno to the ideas of matter that had been formulated by the Milesians, Leucippus and Democritus produced a new philosophy—materialism. Their thesis was that all reality consists of hard indivisible particles, moving and colliding in empty space. This was the first philosophical or scientific statement of the atomic theory. But in this Greek form, the theory is somewhat different from later versions. And it is important not to confuse it with later philosophical ideas or with the theories of twentieth-century atomic physics.

When Democritus of Abdera was a young man, he journeyed to Athens, hoping to talk with Anaxagoras, the leading scientist and philosopher of the circle of artists and intelligentsia that Pericles, the Athenian statesman, had gathered around him. But the eminent older man had no time for a bright young theorist from a foreign city and did not see him. Disappointed, Democritus wrote, “I came to Athens, and no one knew me.”¹ How different he would find the trip today, where the main approach to the city from the northeast runs past the impressive “democritus nuclear research laboratory.” The name is a reminder that ancient Greece was the original home of the “atomic theory,” and that Democritus was its first great developer. It is to variations on the theme of Democritus' ideas that modern science and technology owe much of their spectacular development; and it was atomism that provided the final concepts needed for materialism to appear as a powerful and coherent system of philosophy.²

Credit for the invention of this theory is given to a philosopher named Leucippus, but we know almost nothing about him, and it was in the systematic explanation and applications of Democritus that the theory became stabilized and influential.³

Democritus of Abdera lived about 400 b.c. He lived at the same time as Socrates, and we are therefore ignoring chronological order when we follow the accustomed practice of discussing him as a pre-Socratic philosopher. But in a way it is entirely reasonable to do so, for Democritus represents the final synthesis of ideas that brought to systematic completion the Milesian effort to understand the underlying material components and mechanisms of nature. Socrates began a revolution in thought by rejecting the claim that science can answer all questions of ethics, human life, and philosophy.

There is something not unlike William James's division of philosophers into “tough- and tender-minded,” in the ancient world's contrast of Heraclitus and Democritus as the weeping and laughing philosophers: “Heraclitus weeps, and Democritus laughs, at all things.”

Of the events of Democritus' life we know little; the one personal item is his remark quoted above: “I came to Athens and no one knew me”—a clear record of unappreciated genius that has been sympathized with by many a later scholar. Of his thought, we know a good deal, for his atomic theory was criticized extensively by Aristotle and quoted approvingly by Epicurus (whose extensive philosophic “Letter to Herodotus” has been preserved in the medley of lives and opinions in Diogenes Laërtius' book).⁴

The atomic theory as Democritus developed it was a combination of the Milesian science, Eleatic logic, and probably the development of technology that preceded it.⁵ Long before Leucippus or Democritus developed the notion of atoms, others had suggested that the physical world is made up of small particles. Empedocles had suggested that each of “the elements” comes in small particles of definite size and shape. This idea in turn traces back to the Pythagorean notion of small “regular solids” as the “molecular parts” of nature. Earlier, the Pythagorean attempt to bring mathematics and physics together by building a physical world out of points led in this same direction. Most important in the background of this theory, however, must have been the use of mechanical models to study natural process, which was introduced by Anaximander. In the model, a natural phenomenon is duplicated by the mechanical interaction of small, separate “parts.” Therefore, it is tempting, when one wonders why model-building works, to test the hypothesis that the model is like nature because nature, too, is a complex combination of small parts that interact mechanically. This notion gains plausibility when technology shows that mechanisms can perform functions of a much more complex kind than earlier thinkers had imagined.

The essential ideas of Greek atomism as a physical theory are four: first, that matter comes in separate, smallest particles which are “uncuttable” (atoma- “unable to be cut”); second, that an empty space exists, in which these particles move; third, that the atoms differ only in shape and volume; fourth, that all change is the result of transfer of momentum by the moving atoms and such transfer can occur only by contact—there is, of course, no “action at a distance” in this scheme.⁶

The atoms of this theory are small, hard chunks of being (which, like the One Being of Parmenides, are indivisible, because there are no inner veins of not-being along which they could be “cut”). They have none of the “secondary” qualities—color, flavor, and so on—that we experience, but only shape and extension. (The idea of a qualitatively neutral matter is finally clearly formulated here.)

The atoms differ from each other, singly and in their combinations, “in shape, position, and order.” Thus, A differs from B in shape; N from Z in position; AZ from ZA in order.⁷ These particles come in all sorts of shapes, for, as Democritus argues, “There is no reason why they should have one shape rather than another.” They have always been in motion, and as they move about they collide; sometimes they “interlock” and hold together; sometimes they “rebound” from a collision.⁸ (The Roman poet Lucretius, trying to present a popular, imaginative picture of atomism, pictures “hooks” on the atoms that fasten them together.) All change is ultimately, therefore, change of place and transfer of momentum among these hard particles, and all objects are aggregates packed together in more and less stable patterns.

This notion of all change as a transfer of motion or change of “packing” among differently shaped, hard particles offered an immediate and satisfying explanation of many phenomena that physics wanted to explain.

First of all, consider condensation and rarefaction, changes that have continued to play a central part in physics ever since Anaximenes. If density depends on the relative amount of empty space between the particles of a substance, it is easy to see how pressure leads to condensation, while bombardment by small “fire” particles will spread the atoms apart, leading to rarefaction. And, in principle at least, science has found no more satisfying explanation of differences and changes in density.

The Ionian accounts of the formation of the world by a “spinning vortex,” in which different elements collect in different levels because of their respective mass, worked excellently when the vortex was reinterpreted as made up of many fine particles. It could be argued, with close analogies to experience, that collisions would tend to make the smaller atoms “rebound” further, gradually forcing them to the outside. Empedocles' analysis of “pores and effluences” could be taken over, and was much more satisfactory when the pores were genuinely “empty spaces” in latticeworks of atoms. Anaximander's “models” were, of course, the strongest argument in favor of this new approach to physical reality; for the atomic theory could explain the fact that nature behaved like a machine because it really was a complex mechanism.

So far, the new theory could synthesize and improve on all of the developments of physics up to its inception. There seemed no sharp limit to the phenomena it could explain. In principle, the atomic theorists believed that physics was identical with philosophy; that to the question, What is being?, science had finally found the answer, “In reality, nothing exists but atoms and the void.”

The logical and philosophical background of this new theory played a crucial part in the emergence of atomism as a systematic materialistic philosophy, rather than a specialized physical theory. The scientists of Ionia and the logicians of Elea were almost equally responsible for this. Tracing the line back to Parmenides, the reasoning leads directly to atomism, in the following way:

1. Parmenides had shown to the satisfaction of the atomic theorists that the existence of change, or even the appearance of change, required that being be many, not one; and, if many, divided by not-being into its separate parts;

2. But common sense and Ionian science made it clear that “nature” does change, if not really, in some abstract sense, at least apparently;

3. Therefore, reality must be divided into many parts; and not-being must exist as their separator.

(As a matter of fact, this line of argument, which Democritus accepts, had already been outlined by Melissus of Samos, a philosopher who followed the ideas and methods of Zeno and Parmenides, but Melissus had gone on to reject the conclusion as absurd. since it asserted the existence of not-being. Leucippus and Democritus, on the other hand, accepted the conclusion as actually true, since it was a necessary condition for the appearance of change.)

This Eleatic ancestry also shows in the clear, rigorous logic by which the characteristics of atoms and space are deduced. The atoms are in fact small chunks of Parmenidean “being,” and each one has the properties of indivisibility, homogeneity, qualitative neutrality that Parmenides had ascribed to his One Being. If they were otherwise, the atoms would necessarily have some not-being within them, and so would be, not single particles of matter, but collections of several parts. Empty space is Eleatic not-being: it is defined as having no resistance, density, or cohesion: it cannot, therefore, do or transmit anything, since “nothing comes from nothing.” Any interaction must be the result of two units of being coming together.

The theory thus synthesizes earlier traditions into a new philosophy that has methods and logical rules of its own. The way to understand a subject matter, it assures us, is to analyze every subject matter into its least parts and to find their pattern of combination. If the theory is right, there will always be such parts, and phenomena can always be explained and duplicated by study of their mechanical interaction.

The proponents of the atomic theory further claimed that it could be used to explain medicine, psychology, ethics, and the theory of knowledge, as well as physics and chemistry. In these extensions it sometimes ran into difficulties—for example, in ethics its idea of absolute determinism was hard to adapt to the notion of freedom of choice. But it also had some remarkable successes. For example, in medicine, the doctors and surgeons of that day found that the atomists' idea of treating the body as a complex machine fitted their own practical knowledge of the body's mechanics. It was clear that the workings of the muscular and skeletal system, the ebb and flow of blood (they did not, of course, know of its circulation), the effects of damage to the brain could all be mechanically explained. The processes and functions involving an interaction of the mind and body were obviously more complex. For example, there were patients who complained of pain, though physically there was nothing wrong with them; their trouble had a psychological origin. It was not clear then—and still is not clear today—how such phenomena as these could be reduced to mechanical explanation. But that they could, somehow, be so reduced the atomists were certain.

The old indecisions about psyche, reflected in attempts to make the soul pneuma or aer—but still to hold religious views that would make it immortal—or to make psyche a part of the regular order of the physical world—but still have it initiate motion by a kind of “free decision” to act—had found a decisive resolution. The self was no exception to the total structure of reality; it was corporeal and part of nature, and only illusion and wishful thinking had led mankind to believe in its freedom or immortality. The soul, because of its sensitivity and activity, was supposed to be made up of particularly small, mobile atoms (probably spherical to account for their mobility), which responded by inner movement to the impacts of sensation from the outer world.⁹ When, after a disturbance, the soul moved back into equilibrium, its motion was amplified and transmitted to the body, and also was transmuted into consciousness and thought.

The theory provided a new tool for exploring the mechanism of sensation. Since all “action” is the result of contact, sense perception was explained as the impression made on the senses by atoms from outside. Visible surfaces, for example, radiated atomic films that moved through the air and struck the eye. The clarity of vision depended both on the strength of this constant radiation and on the state of the medium. If the air atoms between the observer and the object were moving violently, the image would be distorted. Even if it were not moving violently, there would be some friction. The corners of the film traveling from a square tower would be knocked off: the eye would receive the impression of a round tower. For transmission and distortion of visual images and sound, for an analysis of touch and taste, the theory gave new precision to accounts of sensation and illusion. Philosophers have never forgotten the new sharpness which this application gave to accounts of the work of the senses, and of the different “perspectives” that objects present to us under different conditions of observation.¹⁰

Consistent with their philosophical position, the atomic theorists treated so-called secondary qualities (warmth, weight, color, taste), not as objective properties of things, but as a subjective contribution by the observer. All of these exist only “by convention,” writes Democritus. “By convention”—here is the opposite of existing “in reality” or “by nature.” The phrase extends the notion of social custom and law—distinctively human constructions—to the senses of the observer who clothes the neutral outer world, which consists of “nothing but atoms and the void,” with its apparent qualities. There are some early and rather unsatisfactory suggestions in Democritus' fragments of the way in which different “colorless” or “black-and-white” configurations of atoms are perceived as having color.

In the field of ethics, the price of consistency seems rather high. Since all events are the mechanical result of physical chains of causality (one of the two surviving fragments of Leucippus says, “Nothing occurs by chance, but all is from necessity”), there is no place for human freedom in this scheme. Neither is there any way for a purpose to be explained, and there is no assurance, on the basis of this theory, that observations from the past will have any relevance in the future: the theory will accept only direct observation as evidence, and the future can never be directly observed. On the other hand, the theory is an excellent antidote to the superstitious component of the then current religious notions.

Various sayings, attributed to Democritus, show how atomism was able logically to connect itself with ethical recommendations. According to these, the soul will either be disturbed, so that its motion affects the body in a violent way, or it will be at rest, in which case it regulates thoughts and actions harmoniously. Freedom from disturbance is the condition that causes human happiness, and this is the ethical goal. A society in which individual men meet and associate like atoms will be stabilized when collisions are kept to a minimum.

It may seem strange to find, in the ethical fragments of Democritus, statements about what we ought to choose or to do, for the theory leaves no place for human freedom of choice. Sometimes this problem is met by saying that because of our ignorance, we seem to have freedom, since we do not know all of the small contributing causes that made a given decision inevitable. In the light of our illusion, we make moral judgments, administer justice, and feel responsible for our own destinies. (To dismiss human freedom, in order to keep the explanation of reality simple and precise, is not satisfying to those for whom ethics is the most important part of philosophy. Later, Epicurus and his school added the notion that the atoms sometimes “swerve” unpredictably, in an attempt to give freedom and chance some foundation in natural science.)

Ethics and politics based on an atomist philosophy are clear and realistic; it is tempting to develop them in this way. Nevertheless, throughout the history of Western thought, no one has satisfactorily reconciled his notion of human nature with rigorous physical necessity. Materialism as a philosophy, based on atomism as its scientific application, has remained ever since Greek times an important and attractive speculative synthesis. There was a period of eclipse during the Middle Ages, because materialism so evidently went contrary to the Christian religion, but there have been three different versions of the theory: the Greek original, the later Roman adaptation of Epicurus and his school, and our contemporary interpretation. … What is particularly interesting about these three variations on a philosophic theme is the different excellences of each version: Democritus' atomism is, of the three, the most clear and rigorous in its logic and its deductions; Epicurus' atomism is less interested in logical elegance than in the ethical implications of atomism, and the theory is reconstructed around these ethical applications; our contemporary concern is less with the logical rigor, or the moral impact of our theory, than with the physical applications for description and control. We may now be moving toward a theory that will combine the excellences of each of these three.¹¹ …

Four more specific criticisms might also be noted here as suggesting limits to the theory—and criticisms continue to be made.¹²

First, there is the criticism that in an atomist's universe, there can be no theory at all.¹³ For to claim that a theory is generally true and that people should believe it, presupposes a theorist who has examined the evidence and chosen the best explanation from among alternatives. But if “all is from necessity,” including all psychological processes, what any man thinks is simply a necessary, mechanical outcome of previous conditioning. The objection, notice, is, not that someone who believes the atomic theory is wrong, but only that he is inconsistent in holding that this belief can represent more than a personal reflection of his past experience and that he, therefore, has no right to say that anyone else ought to agree with him.

Second, there is the question of whether the so-called secondary qualities can really be relegated to existence “by convention.”¹⁴ To explain how a black-and-white world can appear colored, for example, scientists have devised excellent laboratory experiments in which patterns built from colorless elements show how the observer perceives color. But it is sheer Milesian absentmindedness to think that this explains how I perceive color. The scientist, treating his experiment as a model of the brain, forgets his own part in it. He can show, granted, that a pattern of colorless impulses can look colored, but he has not shown how the observer knows it has this color. What, in the model of the brain, corresponds to the experimenter in the laboratory, who “sees” the color emerge from the neutral pattern?

Third, there is the question of whether “empty space” is an intelligible scientific concept at all.¹⁵ If like Democritus we treat it as pure not-being, then can we say that it “separates” the atoms that move about in it? This third objection does not apply, as the first two do, so directly to our modern theory as to the two older versions.

Fourth, there is the objection that there is our own awareness of our freedom, responsibility, and sensitivity to value and purpose. Here the atomic theory may be in the same position that Eleatic philosophy confronted with its denial of motion. Even if ultimately these things are an illusion, isn't it necessary for an adequate theory to show how it is possible for the illusion to appear? And can this be done by any theory that supposes at the outset that there is no place in reality for freedom or value?

Perhaps the first atomic theorists were too optimistic in thinking that their ideas could answer all of the questions of philosophy. In the following chapters, we will see how a new attention to the human observer led to the different speculative synthesis of Platonic idealism and the final attempt of Aristotle to combine Platonism and materialism, which ends the Hellenic epoch of Greek thought.

As a final comment on the relation of technology to the atomic theory, I should like to note that the atomic theory has always been useful when applied to experience. It is a particularly useful view for the inventor or engineer who wants to get a set of mechanical parts to work together automatically and perform some useful function. Would the theory have seemed plausible and remained so intellectually important in a culture with no technology to give it imaginative plausibility and concrete illustration? One would certainly think not, and the fact that in ancient India atomism was thought of as a theoretical position but discarded as implausible matches this expectation.¹⁶ But until recently we had no notion of the true ancient Greek attitude toward technological gadgetry. Classical literature offered several references deprecating arts and crafts and almost no passages describing inventions or equipment. On the basis of this evidence, we would have had to picture the classical atomist as a very strange human being, able to be as fascinated by abstract mechanical design as we are but without any concrete experience with mechanisms.

New archeological evidence shows, however, that by the time of Leucippus and Democritus there was enough use of mechanism to make the analogy of ancient and modern atomic theorists plausible. Factors partly of custom, regulating what themes were or were not the sort of thing to put in book form, partly of supply and demand, determining what available written works would be best sellers and hence recopied and preserved, operated to cause a gap in the older picture. For a clear, demonstrated tradition of scientific apparatus, we are still about fifty years short of closing the gap between Hellenistic and Hellenic periods. But for the discovery of a number of more modest devices that show exactly what we want to know, 1957 in the Athenian Agora proved a decisive year.¹⁷

Aristotle in his Constitution of Athens, itself not recovered until the turn of the present century, describes the equipment and procedure used in impaneling jurors and deciding cases in court. His description has overtones of a Rube Goldberg dream. In 1957, archeologists first discovered ancient equipment that confirms Aristotle's statements. Let us look at one or two of these applications of mechanical ingenuity to insure legal impartiality. The American voting machine will be seen to have an interesting Athenian ancestor, both in the problem necessitating its invention and the lever-gear-and-wheel solutions.

A secret ballot was essential, if jurors were not to be criticized, intimidated, or assassinated for voting the wrong way. And a single ballot for each juror was similarly essential if someone with a dozen extra ballots up his sleeve was to be prevented from dropping them all in the box. The Greeks devised voting tokens to meet the first requirement. Identical in appearance—round wheels, with short shafts sticking out at each side—were these “pebbles” (a name preserved from a simpler time) used in voting. They differed only in that the shaft of one was solid, that of the other hollow: the juror was required to hold his tokens with thumb and finger over the shafts, so that no one else could see the difference. (A further refinement is still not wholly understood: the clerk was required to put the two ballots “on a lampstand” from which they were picked up, in the manner just described, by the juror.) Second, to insure that only a single vote be cast, the voting cask had a top with a slot exactly designed to admit only one disk-and-shaft token. The essential principle of the coin-operated slot-machine or the modern telephone has thus an ancient Athenian ancestry. A special tally board was used to count the ballots, and a courtroom water clock officially measured pleading time.¹⁸

The Greeks took it as a practical axiom that, if anyone knew who the specific jurors would be, no case would be impartially decided. To rule out the possibility of coercion a splendid selection-by-lot mechanism had been invented and mass-produced; twenty were required in preparing for a day in court. So far as I know, no actual traces of the other courtroom devices have been found: a hundred hoppers holding acorns, each lettered from A to L; colored staves used to route jurymen to the courtroom where they were allocated; tokens entitling jurors to payment on surrender to the court; some way of standardizing fractions of a day that allowed for case presentation as between the day-lengths of December and July. But even without these, the documents and finds to date confirm the philosophically interesting hint: that the Greek world, at the time of the atomic theory, had enough mechanical ingenuity and gadgetry to give some concrete content to the vision of reality as a large congeries of small indivisible wheels, slots, and shafts in some magnificent machine.

Notes

1. DK A9; B116.

2. The tremendous historical importance of the atomic theory hardly needs documentation; see, for example, Sambursky, op. cit., pp. 105 ff. (where however the Greek and Roman versions are combined; they are distinguished and summarized on pp. 128 ff.).

3. For Leucippus, see Kirk and Raven, op. cit., p. 403; C. Bailey, The Greek Atomists and Epicurus, Oxford, 1928; Leucippus in DK B1, B1a, B2.

4. Book X, on Epicurus, was copied by Diogenes Laërtius from contemporary primary source material; his treatments of the Epicureans and the Stoics are reliable and important. Epicurus' “Letter to Herodotus,” which Diogenes Laërtius quotes, is an excellent summary of Epicurus' doctrine.

5. Here again we have difficulty in judging the exact balance between pure theory and experiment, or at least observation, that went into the makeup of this theory. See above pp. 88 ff. and the divergent views of Sambursky and Claggett. Also see the end of the present chapter, below, for some evidence that the technology of the time would have made close interaction of the theory and immediate observation possible.

6. DK B9. Cf. M. Jammer, Concepts of Space, with a Foreword by A. Einstein, Cambridge, Mass., 1954. On the reasons why atoms (pieces of pure “being”) can't be “cut,” compare with Parmenides' rejection of plurality, above.

7. Aristotle, Met. 985b13; DK, Leucippus, A10.

8. All shapes, endless motion: Aristotle, loc. cit.

9. Soul atoms finest: Aristotle: De Anima.

10. Emanation theory of perception; compare the “pores and particles” of Empedocles, above, Ch. VIII.

11. In the following table, the Greek atomic theory is reconstructed from fragments and reports of Democritus; the Roman version from Epicurus' Letter, in Diogenes Laërtius; the contemporary is a composite based on a consensus of a number of sources, and on some discussions with colleagues in physics at Yale.

12. Two of the four criticisms that follow are cited in modern formulation, where they are clearer and stronger than in their classical occurrences.

13. For the “no theory” objection, see N. P. Stallknecht's presentation of this point in “Descartes,” Stallknecht and Brumbaugh, Spirit, pp. 252-54.

14. For the “no secondary qualities” objection, see Whitehead's statement, SMW, chap. v.

15. Aristotle is already clear on the “empty space” objection; see his proof that there is no “void,” to which he devotes Physics IV, 213A12 ff.

16. For atomism in India, see the account of the Charvaka school in Radhakrishnan, op. cit.

17. For the excavations and finds, see the Guide to the Agora, 2nd edition, published by the American School of Classical Studies in Athens, Athens, 1963.

18. Aristotle, Aristotle's Constitution of Athens, trans. with notes by K. von Fritz and E. Kapp, New York, 1950, paragraphs 63-69, with notes.