"Pre-Socratic" is the term commonly used (and the one that will be used here) to cover those Greek thinkers from approximately 600 to 400 BCE who attempted to find universal principles that would explain the whole of nature, from the origin and ultimate constituents of the universe to the place of man within it. Yet 400 was the last year of Socrates' life, and among the Sophists, who are also excluded, Protagoras and Gorgias were older than he and others were his contemporaries. "Pre-Socratic" therefore indicates not so much a chronological limit as an outlook and a range of interests. This outlook Protagoras and Socrates deliberately attacked, condemning natural philosophy as worthless compared with the search for a good life, the discussion of social and political questions, and individual morality. Socrates also dismissed its explanations as inadequate because expressed predominantly in terms of origins and internal mechanisms. In his view explanation should be functional, looking to the end rather than the beginning. Thus, for the last sixty or so years of the fifth century, both points of view existed, and a lively controversy went on between them. It was not that the natural philosophers excluded human nature from their investigations but that they saw man and society in a larger framework, as a particular late stage in cosmic development, whereas the others deliberately turned their backs on the external world. The universal and speculative character of pre-Socratic thought was also combated by some of the fifth-century medical writers, and it was in the fields of physiology and hygiene that observational science reached its highest point in this period.
Nature of the Evidence
Before attempting to describe the pre-Socratic doctrines, it is necessary to emphasize the peculiar nature of our sources of knowledge. None of the pre-Socratics' works has survived independently. We have a few references in Plato, some more systematic discussion in Aristotle, and information from later compilers and commentators of which the greater part goes back to a history by Aristotle's pupil Theophrastus. Actual quotations occur and are in some cases extensive, as with the prose fragments of Heraclitus and the 450 surviving lines of Empedocles. Yet, from Aristotle onward, the men who passed on this information were not historians in the modern sense but wrote from a particular philosophical viewpoint (most often Peripatetic), searching the past for anticipations of their own ideas and selecting and arranging their material accordingly. The task of reconstruction and interpretation is thus very different from and more precarious than that of interpreting a philosopher whose original writings are still available for study.
The Milesian School
Pre-Socratic philosophy differs from all other philosophy in that it had no predecessors. Philosophy has been a continuous debate, and even highly original thinkers can be seen developing from or reacting against the thought of a predecessor. Aristotle is unimaginable without Plato; Isaac Newton, without René Descartes, Johannes Kepler, Galileo Galilei, and many others. But with the Greeks of the sixth century the debate begins. Before them no European had set out to satisfy his curiosity about the world in the faith that its apparent chaos concealed a permanent and intelligible order, and that this natural order could be accounted for by universal causes operating within nature itself and discoverable by human reason. They had predecessors of a sort, of course. It was not accidental that the first pre-Socratics were citizens of Miletus, a prosperous trading center of Ionian Greeks on the Asiatic coast, where Greek and Oriental cultures met and mingled. The Milesian heritage included the myths and religious beliefs of their own peoples and their Eastern neighbors and also the store of Egyptian and Babylonian knowledge—astronomical, mathematical, technological. The influence of this heritage was considerable. Yet the Milesians consciously rejected the mythical and religious tradition of their ancestors, in particular its belief in the agency of anthropomorphic gods, and their debt to the knowledge of the East was not a philosophic one. That knowledge was limited because its aim was practical. Astronomy served religion; mathematics settled questions of land measurement and taxation. For these purposes the careful recording of data and the making of certain limited generalizations sufficed, and the realm of ultimate causes was left to dogmatism. For the Greeks knowledge became an end in itself, and in the uninhibited atmosphere of Miletus they gave free play to the typically Greek talent for generalization, abstraction, and the erection of bold and all-embracing explanatory hypotheses.
Consciously, the revolt of the Milesian philosophers against both the content and the method of mythology was complete. No longer were natural processes to be at the mercy of gods with human passions and unpredictable intentions. In their place was to come a reign of universal and discoverable law. Yet a whole conceptual framework is not so easily changed. Poetic and religious cosmogonies had preceded the schemes of the Milesians, and the basic assumptions of these can be detected beneath the hypotheses of their philosophic successors. Nevertheless, the achievement of abandoning divine agencies for physical causes working from within the world itself can hardly be overestimated.
It was common to the mythologies of Greece and neighboring civilizations (and, indeed, to others) that the world arose from a primitive state of unity and that the cosmogonic process was one of separation or division. This was the first act of the Hebrew Creator. In the Babylonian Enuma Elish the original state of the universe was an undefined mass of watery cloud. The Greek theogony of Hesiod speaks of Heaven and Earth, conceived as anthropomorphic figures, lying locked in an embrace until their son forced them apart as Marduk formed heaven and earth by splitting apart the body of the monster Tiamat. Euripides relates an old tale according to which earth and heaven were once "one form" and after their separation brought to birth the whole variety of living things. In Egypt (like Babylonia, a river culture) everything arose out of the primeval waters.
It is not surprising, therefore, that the first people to seek a universal explanation of the world along rational lines assumed that it was in substance a unity from which its variety had been produced by some process of segregation. The key, they thought, lay in identifying the single substance that must satisfy the condition of being able to produce variety out of itself. Thales (active in 585 BCE), who chose water or moisture, may still have had the myths at the back of his mind. For him the earth floated on water as it did for the Egyptians. Little else certain is known of him, and we can only guess at his reasons. Water can be seen as solid, liquid, and vaporous. Aristotle thought it more probable that Thales was influenced by the essential connection of moisture with life, as seen in such substances as semen, blood, and sap. With the removal of external personal agents, the world must initiate its own changes, and at this early stage of speculation the only possibility seemed to be that life of some kind is everywhere and that the universe is a growing, organic structure. This may be the explanation of the saying attributed to Thales: "Everything is full of gods."
With Anaximander, Thales' younger contemporary, there emerges the notion of the four primary opposites that later, when the concepts of substance and attribute had been distinguished, gave rise to the four elements adopted by Aristotle and destined for a long and influential history. Anaximander spoke of only the hot and the dry, which were inevitably in conflict with the cold and the wet. This led him to a momentous idea. The original substance of the universe could not be anything definitely qualified like water, for how could the cold and wet produce their opposites, the hot and dry? Water quenches fire; it cannot engender it. Prior to all perceptible body there must be an indefinite something with none of the incompatible qualities implied by perceptibility. Although still regarding all that exists as corporeal, Anaximander is the first to find ultimate reality in the nonperceptible.
This primary substance he called the apeiron, a word of many meanings all related to the absence of limits—everlasting, infinite, indefinite. Because it was imperishable, the origin of all things, and the author of their changes, he called it (says Aristotle) divine. From it all things have been "separated out," though in what sense they were previously "in" it while the apeiron itself remained a unity is a question that probably did not present itself to him. Somewhere in the apeiron, Theophrastus asserts, a "germ" or "seed" of hot and cold was separated off, and from the interaction of these two flowed the whole cosmic process. A sphere of flame enclosed a moist mass, more solid at the center where the earth formed, vaporous between. The sphere burst into rings around which the dark vapor closed, leaving holes through which we see what appear as sun, moon, and stars. Wet and dry continue to separate, forming land and sea, and finally life itself is produced by the same action of heat (sun) on the cold and moist portions of the earth. The first animals were born in water and crawled onto dry land. Human infants were originally born and nurtured within the bodies of fishlike creatures, for under primitive conditions unprotected babies could not have survived.
Earth, a flat cylinder, hangs freely in space because of its equal distance from all parts of the spherical universe. The sun is the same size as Earth. Eclipses are caused by the closing of the holes in the vapor tubes of the sun and moon. In this first of all attempts at a rational cosmogony and zoogony, the sudden freedom from mythical modes of thought is almost incredible.
Further reflection led Anaximenes, the youngest member of the Milesian school, to a different conclusion about the primary substance: It was air. In its elusiveness and invisibility as atmospheric air, it could almost match the apeiron, and, whereas apeiron, once differentiated into a universe, could no longer be so called, air could become hotter and colder, rarer and denser, and still remain the same substance. Moreover, this theory allowed Anaximenes to break with the notion of separation, which was, at bottom, mythical, and account for the universe by the extension of a known natural process. This was condensation and rarefaction, the former of which he associated with cold and the latter with heat. Air as it rarefies becomes fire; condensed, it turns first to wind, then to cloud, water, earth, and stones. In other words, it is all a question of how much of it there is in a given space, and for the first time the idea enters science that qualitative differences are reducible to differences of quantity. This is Anaximenes' main achievement, although there is no evidence that he applied the principle with any mathematical exactness.
With air as his basic, self-changing substance, Anaximenes could find room for the ancient belief that life was identical with breath. Macrocosm and microcosm were animated by the same principle: "Just as our soul, which is air, integrates us, so breath and air surround the whole cosmos."
The few details that we have of his cosmology suggest that compared with Anaximander's, it was reactionary and timid. His contribution lies elsewhere.
Pythagoras (c. 570–490 BCE) was also an eastern Greek but migrated from his native Samos to Croton in southern Italy. As a result the western or Italian Greek philosophers, even when not actual members of his school, became known for a characteristic outlook very different from that of the materialistic and purely rational Milesians and stamped with the impress of his remarkable genius. He founded a brotherhood dedicated to philosophia (the word was believed to be his invention) as a way of life, with a strong religious, and also a political, element. Philosophically, his importance lies in the shift of interest from matter to form. Inspired, it is said, by the discovery that the musical intervals known to the Greeks as consonant (and marked by four fixed strings on the seven-stringed lyre) were explicable in terms of ratios of the numbers 1 through 4, Pythagoras saw the universe as one glorious harmonia, or mathematico-musical structure. Number was the key to nature. This idea had incalculable consequences for science even if it led at the time to some rather fanciful equations of natural objects and moral qualities with particular numbers. In spite of that, by the time of Socrates the school had made real progress in mathematics. Since the cosmic harmony included everything, all life was akin. The soul was immortal and underwent a series of incarnations, both human and animal. Philosophy was the effort to understand the structure of the cosmic harmony, with the ultimate aim of integrating the philosophic soul more closely into that harmony on the principle that knowledge assimilates the knower to its object. This aim also demanded the observance of certain religious precepts of which the most important was abstention from animal food.
Heraclitus (active c. 500 BCE) objected to the Pythagorean emphasis on harmony, maintaining that, on the contrary, strife and opposition were the life of the world. Life was maintained by a tension of opposites fighting a continuous battle in which neither side could win final victory. Thus, movement and the flux of change were unceasing for individuals, but the structure of the cosmos remained constant. This law of individual flux within a permanent universal framework was guaranteed by the Logos, an intelligent governing principle materially embodied as fire, the most subtle element and identified with soul or life.
Philosophy had thus far meant the search for an essentially simpler reality underlying the bewildering confusion of appearances. The answers fell into two broad categories, matter and form: Reality was a single material substance (the Milesians) or an integral principle of structure that could be expressed in terms of numbers (the Pythagoreans). Heraclitus, with a statement like "You cannot step twice into the same river," reaches the logical conclusion of the materialistic answer. The water will be different water the second time, and, if we call the river the same, it is because we see its reality in its form. The logical conclusion of form-philosophy is the opposite of flux—namely, a belief in an absolute, unchanging reality of which the world of change and movement is only a quasi-existing phantom, phenomenal, not real. (This conclusion was reached in the idealism of Plato, which was largely of Pythagorean inspiration.)
Eleatic School: Unity of Reality
At this time the direction of philosophy was changed by the precocious and uncompromising logic of Parmenides of Elea, who was perhaps twenty-five years younger than Heraclitus. For the first time abstract, deductive reasoning is deliberately preferred to the evidence of the senses: "Ply not eye and ear and tongue, but judge by thought." He concluded that if there is any reality at all (in the language of his time, if "it is"), it must be (1) one only (for if more than one, its units could be separated only by "what is not"); (2) eternal and unchanging (for to speak of change or perishing is to say that reality at some time "is not" what it was, but to say of "what is" "it is not" is contradictory and impossible); (3) immovable (this follows from his statement that "all is full of what is"; since it cannot admit discontinuity or lack of homogeneity and since "what is not is not," the spatial requirements of locomotion cannot be provided).
In this way he "proved" that, on the premise of his predecessors that reality is one, differentiation of the real can never occur. It remains one—a timeless, changeless, motionless, homogeneous mass, which he compared to a sphere. The multiple, changing world of appearances is an illusion of our senses. Only as a concession to human weakness, and in recognition of our practical need to come to terms with the show of a natural world, did he append a cosmology of the conventional type, beginning with two principles, heat-light and cold-darkness. Cosmogony from a single origin was no longer possible, yet he explicitly warns his hearers that reality is in truth a unity and that the cosmos is only a deceitful appearance to mortals.
It is disputed whether the One Reality of Parmenides is material. The question can hardly be answered, since we are still in a period before the distinction between material and nonmaterial could be drawn. The important thing is that it was nonsensible and could be reached only by thought. Parmenides was the first philosopher to distinguish explicitly between the sensible and the intelligible and to condemn the former as unreal. Plato himself, though fully aware of the distinction between material and spiritual, usually preferred to call them sensible and intelligible, and it is very doubtful whether the philosophy of Platonic idealism would ever have been possible without Parmenides.
zeno and melissus
Parmenides had two followers, who, with him, are known as the Eleatic school. Zeno of Elea (born c. 490 BCE) concentrated on a defense of the proposition that reality is one and immovable by the dialectical method of showing up absurdities in the contrary view. His famous paradoxes are aimed at demonstrating the impossibility of plurality and movement. Melissus of Samos (active in 440 BCE) modified Parmenides' ideas to the extent of saying that reality is infinite. He explicitly denied the possibility of empty space (which Parmenides had only hinted at) and said that if there were many things, each would have to have the characteristics of the Parmenidean One. It is therefore probable that the atomists had him especially in mind when they boldly explained the world in terms of space plus tiny entities, each of which had many of the Eleatic qualities—indivisibility, homogeneity, unalterability.
The naïveté of Parmenides' logic and the purely linguistic nature of some of his difficulties seem obvious now, but at the time his questions appeared unanswerable. There were only two ways out: either to abandon monism and admit the ultimate plurality of the real or to admit the unreality of the natural world. The latter solution was Plato's, with his contrast between "what always is and never becomes" and "what is continually becoming (like the flux of Heraclitus) but never truly is." The remainder of pre-Socratic thought is occupied with attempts to save the phenomena by adopting some form of pluralism.
Tthe Pluralists: Empedocles
The first of the pluralistic systems was that of Empedocles (c. 490–430 BCE), a Sicilian poet-philosopher steeped in the Western tradition, with its combination of rationalism and mystical religion so different from the purely scientific outlook of the Ionians. His proposal was the first clear enunciation of the four-element theory. Fire, air, water, and earth are the ultimate roots of all things, themselves ungenerated and indestructible. Everything in nature comes into being and perishes by the mixture and separation of these substances. The first premise is no longer "It is" but "They are." Thus, trees and animals, clouds and rocks, are not mere illusion. However, since they are only temporary combinations of the four "realities" in varying proportions, we can admit that they themselves are not "real." Nor need the forbidden concepts of "becoming" and "perishing" be invoked; mixture and separation will account for all. Locomotion is, of course, necessary, and, although he accepts the Eleatic denial of empty space, Empedocles seems to have thought that this could occur by some reciprocal and simultaneous exchange of place, the whole remaining full.
The four elements are not self-moving (another concept that Parmenides had rendered difficult), and the blend of mystic and rationalist in Empedocles appears especially in his motive causes. These were two, Love and Strife, the former bringing disparate elements together and the latter drawing them apart. They are in endless opposition and prevail in turn, bringing about a double evolutionary cycle. Under Love all four elements are indistinguishably fused in a sphere; under Strife the same sphere contains them in separate layers. During the contest, when neither Love nor Strife is in complete control and when the elements are partly joined and partly separated, a world like our own is formed. Nothing existent is as yet incorporeal, though Love and Strife are of finer and more tenuous substance than the elements. Their names are no metaphors, nor is their action purely mechanical. Under Love the elements are dear to and desired by one another; Strife makes them grim and hostile. Nothing is purely inanimate, and everything has its share of consciousness.
Besides his poem on nature, Empedocles also wrote a religious one, in which the moral character of Love and Strife is emphasized—Love is good, Strife evil. In the present world Strife is gaining, and men have fallen from a previous blessed state by giving themselves to Strife and sin, above all the sin of killing and eating animals. All life is akin, as it was to the Pythagoreans, and our souls are fallen spirits that must undergo a series of incarnations before they can win back their former state by abjuring Strife and cultivating Love. What the substance of the spirits was is not clearly stated, but most probably in their pure state they were portions of Love that are now contaminated with Strife.
Anaxagoras of Clazomenae (c. 500–428 BCE) brings us back to Ionia both geographically and in spirit. His motive is rational curiosity entirely uncomplicated by religious preoccupations. Even Parmenides, a Westerner like Empedocles, had written in verse and represented his deductive arguments as a revelation from a goddess. In his return to prose, as in his purely scientific aims, Anaxagoras is the heir of the Milesians. At Athens, where he lived until exiled for atheism, he was a member of the brilliant and freethinking circle of Pericles. His prosecution seems to have had a political flavor, but the charge is nevertheless significant: He declared the sun to be not a living divinity but a lump of incandescent rock larger than the Peloponnese.
To save the phenomena without admitting the coming into being or destruction of what exists, he adopted an extreme form of pluralism plus a first cause of motion, which he called Mind. It is described as knowing all things and having the greatest power, and, in order to control the material world, it is entirely outside the mixture of which the material world is formed. It is not easy to be sure whether Anaxagoras is at last trying to express the notion of incorporeal being without an adequate vocabulary or whether he still thinks of Mind as an extremely subtle and tenuous form of matter. At any rate, its separateness from the constituents of the cosmos is emphasized at every turn. In spite of the references to its knowledge and power, it action seems to be confined to the earliest stages of cosmogony, except in the case of living creatures. They are an exception to the rule that Mind is in nothing else, and them it still controls.
In the beginning "all things were together," a stationary mass in which nothing could be distinguished. Mind is the agent that has produced from this an ordered cosmos. It did so by starting a rotatory movement or vortex, which by its own increasing speed brought about the gradual separation of different forms of matter. Anaxagoras's highly subtle and ingenious theory of matter seems to have been especially prompted by the need to explain nourishment and organic growth: How can flesh and hair come out of the not-flesh and not-hair of the food we eat? After Parmenides the coming into being of new substances is disallowed. Anaxagoras answered that there is a portion of everything in everything—that is, every distinguishable substance, in however small a quantity, contains minute particles of every other but is characterized by that which predominates. He boldly asserted the existence of the infinitesimal (which Zeno had denied) in the words: "Of the small there is no smallest."
Perhaps around 430 BCE Leucippus promulgated the much simpler theory of atomism, which was further developed by his famous pupil Democritus of Abdera (born c. 460 BCE). Like the other theories, this one arose in direct response to the Eleatic challenge. Its most striking innovation for its time was the assertion of the existence of genuine empty space. Thus far, everyone had believed that "what is" must be some form of body, and, when Parmenides brought into consciousness the implicit consequence that space, not being "what is," must be "what is not" (that is, nonexistent), his conclusion seemed logically inescapable. Hence, even the atomists had to use the paradoxical expression that it is no more correct to say of "what is" than of "what is not" that it is.
At this particular point in the philosophic debate, this was the only way of expressing the conviction that, though not any kind of stuff, space must be assumed if the plain facts are to be explained. Democritus, said Aristotle, is to be commended for refusing to be dazzled by the abstract logic of Parmenides and for relying on the kind of argument more proper to a natural scientist. Reality consists of innumerable microscopic and indivisible (a-tomos = uncuttable) bodies in motion in infinite space. They are solid and homogeneous but infinitely variable in size and shape. At different places in the infinite, they have collided and become entangled. Projections hook together, convex fits into concave, and so on. Their continued motion sets up a vortex in which the larger and heavier fall into the center and the smaller and lighter are extruded to the circumference; in this way a cosmos is formed. There are many worlds, and not all are similar to our own. The first atomists appear to have provided no separate cause of motion, perhaps because they deemed it sufficient to free the atoms by setting them loose in infinite space. After all, the chief Eleatic arguments against motion had been the continuity of being and the nonexistence of a void.
Only atoms and the void exist. Sensible qualities other than size and shape are subjective, caused by interaction between the atoms of external objects and those in our own bodies. This was worked out in considerable detail. For instance, hard objects have their atoms more closely packed than do soft. Sweet flavors are caused by smooth atoms, bitter and astringent by sharp or hooked. Colors vary according to the positions of surface atoms, which cause them to reflect in different ways the light that falls upon them. Objects are continually throwing off films of atoms, and sight is the reception of these films by the eye. The soul, or life principle, is composed of smooth, round atoms that are even more mobile than the rest and impart to the body the power of motion and cognition, for "soul and mind are the same"—that is, composed of the same kind of atoms. Soul is dispersed throughout the body, alternating with body atoms, but the mind appears to have been a collection of these finest particles that is located probably in the breast. Although the direct objects of sight and hearing, taste and smell, are unreal, they lead the mind to the truth about reality, and Democritus quoted with approval a saying of Anaxagoras: "Phenomena are a glimpse of the unseen."
Ancient atomism (including its revival by Epicurus a century or more after Democritus) has acquired a partly adventitious reputation through its resemblances to nineteenth-century physical theories, but its hard, solid, unbreakable particles have little in common with the ultimate entities of modern science. Its most striking features are the distinction between primary and secondary qualities (upheld by Descartes, Galileo, and John Locke), the explanation of directly observable objects by hypothetical constituents below the level of perception, and the outspoken championship of discrete quanta as opposed to a continuum. Its inadequacy in allowing no mode of action other than direct contact, collision, and interlocking was evident in some physical problems—for example, in its attempted explanation of magnetism and, most of all, in the effort to include within its purview the phenomena of life and thought. The atomic structure of matter has indeed been a fruitful hypothesis, but the intention of its authors is best understood in the context of their time and as an attempt to escape the Eleatic dilemma, rather than as an anticipation of postmedieval science.
Diogenes of Apollonia
The teleological explanation, which one would naturally associate with Anaxagoras's adoption of Mind as first cause, appears more strongly in the second half of the fifth century in a less gifted thinker, Diogenes of Apollonia. He put Mind back into the mixture by returning to Anaximenes's idea that the primary substance is air or breath and by identifying this air in its purest (dry and warm) state with intelligence. The regularity of cosmic events he regarded as evidence of intelligent control, going so far as to say that anyone who reflects will agree that all is arranged in the best possible way. Breath is also the life of humans and animals, so that all owe their soul and mind to the same material principle—"a small portion of the god"—which they share in varying degrees of purity. He probably thought he avoided the Eleatic arguments against a materialistic monism by the admission of void, which, by the time he wrote (after Melissus and Leucippus), would in any case be recognized as necessary for the process of condensation and rarefaction by which air produced the variety of nature.
When we consider the grotesqueness of some of the mythological background from which the pre-Socratic thinkers started, we must be amazed by the intellectual insight and firm grasp of universal principles that at their best they were capable of displaying. But a dispassionate assessment of their contribution to the history of philosophy would probably show that, to use a metaphor, although they manufactured many of the pieces and set them on the board, Plato and Aristotle were the first players who learned the rules and started the game. The pieces are those opposed concepts by means of which philosophical discussion is maintained: being and becoming, sensible and intelligible, analytic and synthetic, appearance and reality, time and eternity, materialism and idealism, mechanism and teleology, and so forth. Once these stand out clearly, a philosopher may champion one or the other, but the pre-Socratics could not yet do this. One cannot speak realistically of a controversy among them between, say, materialists and idealists. The achievement of their intellectual effort and controversy was that by the end of this period a clear notion of what was meant by matter and mind, sensible and intelligible, phenomenal and real, and the rest was at last emerging, so that succeeding generations had the set in their hands and could begin the game in earnest. For the first of all philosophers, this was no mean achievement.
Their interests were, of course, in modern terms, as much scientific as philosophical, and in this sphere also they could claim some remarkable results. For instance, before the end of the period the true cause of both lunar and solar eclipses had been discovered (probably by Anaxagoras), and certain Pythagoreans had abandoned the geocentric cosmology, asserting that Earth, the sun, and the planets all circled round a central fire. But it is probably fair to say that their scientific discoveries appeared only as by-products of the main controversies and of the few universal principles from which they confidently deduced even the details of the physical world. The true and lasting discoveries were not picked up and developed as they would have been by post-Renaissance scientists because, owing to the different preoccupations of philosophy at their time, they had no firm basis in established fact and did not in any way stand out from other and, to us, more fanciful assumptions.
See also Alcmaeon of Croton; Anaxagoras of Clazomenae; Anaximander; Anaximenes; Apeiron/Peras; Appearance and Reality; Archē; Chaos Theory; Cosmology; Cosmos; Diogenes of Apollonia; Empedocles; Hen/Polla; Heraclitus of Ephesus; Infinity in Theology and Metaphysics; Leucippus and Democritus; Logos; Materialism; Melissus of Samos; Monism and Pluralism; Orphism; Parmenides of Elea; Philolaus of Croton; Pre-Socratic Philosophy; Pythagoras and Pythagoreanism; Thales of Miletus; Xenophanes of Colophon; Zeno of Elea.
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collections of essays
Allen, R. E., and David J. Furley, eds. Studies in Presocratic Philosophy. Vol. 2: The Eleatics and the Pluralists. London: Routledge & Kegan Paul, 1975.
Curd, Patricia, and Daniel W. Graham, eds. The Oxford Handbook of Presocratic Philosophy. Oxford: Oxford University Press, 2006.
Furley, D. J., and R. E. Allen, eds. Studies in Presocratic Philosophy. Vol. 1: The Beginnings of Philosophy. London: Routledge & Kegan Paul, 1970.
Long, A. A., ed. The Cambridge Companion to Early Greek Philosophy. Cambridge, U.K.: Cambridge University Press, 1999.
Mourelatos, A. P. D., ed. The Pre-Socratics: A Collection of Critical Essays. Garden City, NY: Doubleday, 1974; second printing, with revised introduction and bibliography, Princeton, NJ: Princeton University Press, 1993.
Taylor, C. C. W., ed. From the Beginning to Plato. Routledge History of Philosophy, 1. London: Routledge, 1997.
particular thinkers or schools
Burkert, Walter. Lore and Science in Ancient Pythagoreanism. Translated by E. L. Minar, Jr. Cambridge, MA: Harvard University Press, 1972.
Huffman, Carl A. Philolaus of Croton: Pythagorean and Presocratic, Commentary on the Fragments and Testimonia with Interpretive Essays. Cambridge, U.K.: Cambridge University Press, 1993.
Kahn, Charles H. The Art and Thought of Heraclitus: An Edition of the Fragments with Translation and Commentary. Cambridge, U.K.: Cambridge University Press, 1979.
Sider, David. The Fragments of Anaxagoras. Beiträge zur klassischen Philologie, 118. Meisenheim am Glan: Hain, 1981.
"Phoenix Pre-Socratics," a series published by the University of Toronto Press, comprises volumes that provide ancient text, English translation, and explanatory comments: (1) David Gallop, Parmenides of Elea, 1984, rev. ed. 1991; (2) Robinson, T. M., Heraclitus, 1987; (3) Inwood, Brad, The Poem of Empedocles, 1992, rev. ed. 2001; (4) Lesher, J. H., Xenophanes of Colophon, 1992; (5) Taylor, C. C. W., The Atomists: Leucippus and Democritus, 1999.
W. K. C. Guthrie (1967)
Bibliography updated by Alexander Mourelatos (2005)