Presocratic Philosophy
First published Sat Mar 10, 2007; substantive revision Mon Jun 22, 2020
The Presocratics were 6th and 5th century BCE Greek thinkers who introduced a new way of inquiring into the world and the place of human beings in it. They were recognized in antiquity as the first philosophers and scientists of the Western tradition. This article is a general introduction to the most important Presocratic philosophers and the main themes of Presocratic thought. More detailed discussions can be found by consulting the articles on these philosophers (and related topics) in the SEP (listed below).
For over a century, the standard collection of texts for the Presocratics has been that by H. Diels revised by W. Kranz (abbreviated as DK). DK provides the original language of the texts, usually Greek or Latin, with translation in German. In 2016, a new collection was published by A. Laks and G. Most with original texts and translation into English (abbreviated as LM; a version with French translations was also published in 2016). In DK, each thinker is assigned an identifying chapter number (e.g., Heraclitus is 22, Anaxagoras 59); then the reports from ancient authors about that thinker’s life and thought are collected in a section of “testimonies” (A) and numbered in order, while the passages the editors take to be direct quotations are collected and numbered in a section of “fragments” (B). Alleged imitations in later authors are sometimes added in a section labeled C. Thus, each piece of text can be uniquely identified: DK59B12.3 identifies line 3 of Anaxagoras fragment 12; DK22A1 identifies testimonium 1 on Heraclitus.
A similar system is adopted in LM. (LM provide helpful concordances to DK.) Section P contains passages dealing with the life and works of the author (overlapping in some ways with DK’s A section); section D includes passages covering doctrine with direct quotations in boldface font (thus overlapping with DKB and somewhat with DKA); and a section R includes reaction to the author (Reception) and texts the editors deem to be ancient forgeries or imitations. Like DK, LM assign an identifying number to each thinker and numbers to each piece of text: LM25D27 picks out Anaxagoras (25) doctrine number 27 (= DK59B12), LM25P37 is the same text as DK59A30, and LM25D94 is DK59A117.
• 1. Who Were the Presocratic Philosophers?
• 2. The Milesians
• 3. Xenophanes of Colophon and Heraclitus of Ephesus
• 4. Parmenides of Elea
• 5. The Pythagorean Tradition
• 6. Other Eleatics: Zeno and Melissus
• 7. The Pluralists: Anaxagoras of Clazomenae and Empedocles of Acragas
• 8. Presocratic Atomism
• 9. Diogenes of Apollonia and the Sophists
• 10. The Presocratic Legacy
• Bibliography
• Primary Sources: Texts and Translations
• Secondary Literature
• Academic Tools
• Other Internet Resources
• Related Entries
- Who Were the Presocratic Philosophers?
Fragmentary evidence complicates our understanding of the Presocratics. Most of them wrote at least one “book” (short pieces of prose writing, or, in some cases, poems), but no complete work survives. Instead, we depend on later philosophers, historians, and compilers of collections of ancient wisdom for disconnected quotations (fragments) and reports about their views (testimonia). In some cases, these sources were themselves able to consult the works of the Presocratics directly. In many others, the line is indirect and often depends on the work of Hippias, Aristotle, Theophrastus, Simplicius, and other ancient philosophers who did have direct access. All of the sources for the fragments and testimonia made selective use of the material available to them, in accordance with their own special, and varied, interests in the early thinkers. (For analyses of the doxographic tradition, and the influence of Aristotle and Theophrastus on later sources, see Mansfeld 1999; Runia 2008; Mansfeld and Runia 1997, 2009a, and 2009b; Laks and Most, 2016.) Despite (or perhaps because of) the fragmentary nature of the evidence, new material occasionally comes to light. In 1962 “The Derveni Papyrus,” probably dating from the second part of the fourth century B.C.E., was discovered in Greece (Betegh 2004, Janko 2001, Kotwick 2017). It is primarily concerned with Orphic religion, including a commentary on a poem attributed to Orpheus. Through the work of scholars to reconstruct and interpret it (see Kouremenos, Pássoglou, & Tantsanaglou 2006) it has become clear that the author of the commentary was familiar with the philosophical theories of the time, and the papyrus has proved valuable to the study of early Greek Philosophy (see, for instance Betegh 2014a and 2014b, and Betegh & Piano 2019). Further new Presocratic material was found in a papyrus from Upper Egypt, now in Strasbourg, that contains texts from Empedocles, some already included in DK, but also previously unknown lines which have complicated our understanding of Empedocles’ thought. (See Martin & Primavesi 1999, and Janko 2001, 2005.) Although any account of Presocratic thinkers has to be a reconstruction, we should not be overly pessimistic about the possibility of reaching a historically responsible understanding of them.
Calling this group Presocratic raises certain difficulties. The term, coined in the eighteenth century, was made current by Hermann Diels in the nineteenth, and was meant to mark a contrast between Socrates who was interested in moral problems, and his predecessors, who were supposed to be primarily concerned with cosmological and physical speculation. “Presocratic,” if taken strictly as a chronological term, is not accurate, for the last of them were contemporaneous with Socrates and even Plato. Moreover, several of the early Greek thinkers explored questions about ethics and the best way to live a human life. The term may also suggest that these thinkers are somehow inferior to Socrates and Plato, of interest only as their predecessors, and its suggestion of archaism may imply that philosophy only becomes interesting when we arrive at the classical period of Plato and Aristotle. Some scholars now deliberately avoid the term, but if we take it to refer to the early Greek thinkers who were not influenced by the views of Socrates, whether his predecessors or contemporaries, there is probably no harm in using it. (For discussions of the notion of Presocratic philosophy, see Long’s introduction in Long (ed.) 1999, Laks 2006, the articles in Laks and Louguet 2002, and Laks 2018.)
A second problem lies in referring to these thinkers as philosophers. That is almost certainly not how they could have described themselves. While it is true that Heraclitus says that “those who are lovers of wisdom must be inquirers into many things” (DK22B35/LM9D40), the word he uses, philosophos, does not have the special sense that it acquires in the works of Plato and Aristotle, when the philosopher is contrasted with both the ordinary person and other experts, including the sophist (particularly in Plato), or in the resulting modern sense in which we can distinguish philosophy from physics or psychology. Yet the Presocratics certainly saw themselves as set apart from ordinary people and also from others (certain of the poets and historical writers, for example, as we can see from Xenophanes and Heraclitus) who were their predecessors and contemporaries. As the fragment from Heraclitus shows, the early Greek philosophers thought of themselves as inquirers into many things, and the range of their inquiry was vast. They had views about the nature of the world, and these views encompass what we today call physics, chemistry, geology, meteorology, astronomy, embryology, and psychology (and other areas of natural inquiry), as well as theology, metaphysics, epistemology, and ethics. In the earliest of the Presocratics, the Milesians, it can indeed be difficult to discern the strictly philosophical aspects of the views in the evidence available to us. Nevertheless, despite the danger of misunderstanding and thus underestimating these thinkers because of anachronism, there is an important sense in which it is quite reasonable to refer to them as philosophers. That sense is inherent in Aristotle’s view (see, e.g., Metaphysics I, Physics I, De Anima I, On Generation and Corruption I): these thinkers were his predecessors in a particular sort of inquiry, and even though Aristotle thinks that they were all, for one reason or another, unsuccessful and even amateurish, he sees in them a similarity such that he can trace a line of continuity of both subject and method from their work to his own. The questions that the early Greek philosophers asked, the sorts of answers that they gave, and the views that they had of their own inquiries were the foundation for the development of philosophy as it came to be defined in the work of Plato and Aristotle and their successors. Perhaps the fundamental characteristic is the commitment to explain the world naturalistically, in terms of its own inherent principles. (For discussions, see Sassi, 2006, 2018.)
By contrast, consider the 7th century BCE poem of Hesiod, his Theogony (genealogy of the gods). Hesiod tells the traditional story of the Olympian gods, beginning with Chaos, a vague divine primordial entity or condition. From Chaos, a sequence of gods is generated, often by sexual congress, but sometimes no cause for their coming to be is given. The divine figures that thus arise are often connected with a part of the physical universe, or with some aspect of human experience, so his theogony is also a cosmogony (an account of the generation of the world). The divinities (and the associated parts of the world) come to be and struggle violently among themselves; finally Zeus triumphs and establishes and maintains an order of power among the others. Hesiod’s world is one in which the major divinities are individuals who behave like super-human beings (Gaia or earth, Ouranos or sky, Cronos — an unlocated regal power, Zeus); some of the others are personified characteristics (e.g., Momus, blame; and Dusnomia, lawlessness). For the Greeks, the fundamental properties of divinity are immortality (they are not subject to death) and great power (as part of the cosmos or in managing events), and each of Hesiod’s characters has these properties (even though in the story some are defeated, and seem to be destroyed). Hesiod’s story is like a vast Hollywood-style family history, with envy, rage, love, and lust all playing important parts in the coming-to-be of the world as we know it. The earliest rulers of the universe are violently overthrown by their offspring (Ouranos is overthrown by Cronos, Cronos by Zeus). Zeus insures his continued power by swallowing his first consort Metis (counsel or wisdom); by this he prevents the predicted birth of rivals and acquires her attribute of wisdom (Theogony 886–900). In a second poem, Works and Days, Hesiod pays more attention to human beings, telling the story of earlier, greater creatures who died out or were destroyed by themselves or Zeus. Humans were created by Zeus, are under his power, and are subject to his judgment and to divine intervention for either good or ill. Hesiod’s world, like Homer’s, is one that is god-saturated, where the gods may intervene in all aspects of the world, from the weather to mundane particulars of human life, acting on the ordinary world order, in a way that humans, limited as they are by time, location, and narrow powers of perception, must accept but cannot ultimately understand. The Presocratics reject this account, instead seeing the world as a kosmos, an ordered natural arrangement that is inherently intelligible and not subject to supra-natural intervention. A striking example is Xenophanes DK21B32/LM8D9: “And she whom they call Iris, this too is by nature cloud / purple, red, and greeny yellow to behold.” Iris, the rainbow, traditional messenger of the gods, is after all, not supra-natural, not a sign from the gods on Olympus who are outside of and immune from the usual world order; rather it is, in its essence, colored cloud. (A good discussion of the Hesiodic myths in relation to Presocratic philosophy can be found in McKirahan 2011. Burkert 2008 surveys influence from the east on the development of Presocratic philosophy, especially the myths, astronomy, and cosmogony of the Babylonians, Persians, and Egyptians.)
Calling the Presocratics philosophers also suggests that they share a certain outlook; an outlook that can be contrasted with that of other early Greeks (see Moore 2020). Although scholars disagree about the extent of the divergence between the early Greek philosophers and their non-philosophical predecessors and contemporaries, it is evident that Presocratic thought exhibits a difference not only in its understanding of the nature of the world, but also in its view of the sort of explanation of it that is possible. This is clear in Heraclitus. Although Heraclitus asserts that those who love wisdom must be inquirers into many things, inquiry alone is not sufficient. At DK22B40/LMD20 he rebukes four of his predecessors: “Much learning does not teach understanding; else it would have taught Hesiod and Pythagoras, and again Xenophanes and Hecataeus.” Heraclitus’ implicit contrast is with himself; in DK 22B1/LM D9 and D110 he suggests that he alone truly understands all things, because he grasps the account that enables him to “distinguish each thing in accordance with its nature” and say how it is. For Heraclitus there is an underlying principle that unites and explains everything. It is this that others have failed to see and understand. According to Heraclitus, the four have amassed a great deal of information — Hesiod was a traditional source of information about the gods, Pythagoras was renowned for his learning and especially views about how one ought to live, Xenophanes taught about the proper view of the gods and the natural world, Hecataeus was an early historian — but because they have failed to grasp the deeper significance of the facts available to them, their unconnected bits of knowledge do not constitute understanding. Just as the world is a kosmos, an ordered arrangement, so too, human knowledge of that world must be ordered in a corresponding way.
- The Milesians
In his account of his predecessors’ searches for “causes and principles” of the natural world and natural phenomena, Aristotle says that Thales of Miletus (a city in Ionia, on the west coast of what is now Turkey) was the first to engage in such inquiry. He seems to have lived around the beginning of the 6th c. BCE. Aristotle mentions that some people, before Thales, placed great importance on water, but he credits Thales with declaring water to be the first cause (Metaphysics 983b27–33), and he then later raises the question of whether perhaps Hesiod was the first to look for a cause of motion and change (984b23ff.). These suggestions are rhetorical: Aristotle does not seriously imply that those he mentions are engaged in the same sort of inquiry as he thinks Thales was. Two other Greek thinkers from this very early period, Anaximander and Anaximenes, were also from Miletus, and although the ancient tradition that the three were related as master and pupil may not be correct, there are enough fundamental similarities in their views to justify treating them together.
The tradition claims that Thales predicted a solar eclipse in 585 BC (DK 11A5/LM 5P9, P10), introduced geometry into Greece from Egypt (DK 11A11/LM 5P4, P5, R11), and produced some engineering marvels. Anaximander is reported to have invented the gnomon (the raised piece of a sundial whose shadow marks time); to have created a sphere of the heavens serving as an astronomical and cosmological model (DK 12A1/LM 6P2, P4, P11); and to have been the first to draw a map of the inhabited world (DK 12A6/LM 6P6, D4). Regardless of whether these reports are correct (and in the case of Thales’ prediction they almost certainly are not), they indicate something important about the Milesians: their interests in measuring and explaining celestial and terrestrial phenomena were as strong as their concern with the more abstract inquiries into the causes and principles of substance and change attributed to them by Aristotle (Algra 1999, White 2002 and 2008). They did not see so-called “scientific” and “philosophical” questions as belonging to separate disciplines, requiring distinct methods of inquiry. The assumptions and principles that we (along with Aristotle) see as constituting the philosophical foundations of their theories are, for the most part, implicit in the claims that they make. Nevertheless, it is legitimate to treat the Milesians as having philosophical views, even though no clear statements of these views or specific arguments for them can be found in the surviving fragments and testimonia.
Aristotle’s comments do not sound as if they were based on first-hand knowledge of Thales’ views, and the doxographical reports say that Thales did not write a book. Yet Aristotle is confident that Thales belongs, even if honorifically, to that group of thinkers that he calls “inquirers into nature” and distinguishes him from earlier poetical “myth-makers.” In Book I of Metaphysics, Aristotle claims that the earliest of these, among whom he places the Milesians, explained things only in terms of their matter (Met. I.3 983b6–18). This claim is anachronistic in that it presupposes Aristotle’s own novel view that a complete explanation must encompass four factors: what he called the material, efficient, formal, and final causes. Yet there is something in what Aristotle says. Aristotle links Thales’ claim that the world rests on water with the view that water was the archē, or fundamental principle, and he adds that “that from which they come to be is a principle of all things” (983b24–25; DK 11A12/LM 5D3, R9). He suggests that Thales chose water because of its fundamental role in coming-to-be, nutrition, and growth, and claims that water is the origin of the nature of moist things.
Aristotle’s general assertion about the first thinkers who gave accounts of nature (and his specific discussion of Thales’ reliance on water as a first principle) brings out a difficulty in interpreting the early Presocratics. According to Aristotle’s general account, the Presocratics claimed that there was a single enduring material stuff that is both the origin of all things and their continuing nature. Thus, on this view, when Thales says that the first principle is water, he should be understood as claiming both that the original state of things was water and that even now (despite appearances), everything is really water in some state or another. The change from the original state to the present one involves changes in the material stuff such that although it may not now appear to be water everywhere (but seems to be airier or earthier than water in its usual state, or its original one), there is no transformation of water into a different kind of stuff (air or earth, for instance). Yet, when Aristotle comes to give what details he can of Thales’ view, he suggests only that for Thales, water was the first principle because everything comes from water. Water, then, was perhaps the original state of things for Thales, and water is a necessary condition for everything that is generated naturally, but Aristotle’s summary of Thales’ view does not imply that Thales claimed that water endures through whatever changes have occurred since the original state, and now just has some new or additional properties. Thales may well have thought that certain characteristics of the original water persisted: in particular its capacity for motion (which must have been innate in order to generate the changes from the original state). This is suggested by Thales’ reported claims that the lodestone (with its magnetic properties) and amber (which when rubbed exhibits powers of attraction through static electricity) have souls and that all things are full of gods. Aristotle surmises that Thales identified soul (that which makes a thing alive and thus capable of motion) with something in the whole universe, and so supposed that everything was full of gods (DK11A22/LM5D10, D11a )—water, or soul, being a divine natural principle. Certainly the claim that the lodestone has soul suggests this account. Given that the analysis of change (both qualitative and substantial) in terms of a substratum that gains and loses properties is Aristotelian (although perhaps foreshadowed in Plato), it is not surprising that the earlier views were unclear on this issue, and it is probable that the Milesian view did not clearly distinguish the notions of an original matter and an enduring underlying stuff (Graham 2006).
The reports about Thales show him employing a certain kind of explanation: ultimately the explanation of why things are as they are is grounded in water as the basic stuff of the universe and the changes that it undergoes through its own inherent nature. In this, Thales marks a radical change from all other previous sorts of accounts of the world (both Greek and non-Greek). Like the other Presocratics, Thales sees nature as a complete and self-ordering system, and sees no reason to call on divine intervention from outside the natural world to supplement his account—water itself may be divine, but it is not something that intervenes in the natural world from outside (Gregory, 2013). While the evidence for Thales’ naturalistic account is circumstantial, this attitude can be directly verified for Anaximander.
In the one fragment that can be securely attributed to Anaximander (although the extent of the implied quotation is uncertain), he emphasizes the orderly nature of the universe, and indicates that the order is internal rather than imposed from outside. Simplicius, a 6th c. CE commentator on Aristotle’s Physics, writes:
Of those who say that [the first principle] is one and moving and indefinite, Anaximander, son of Praxiades, a Milesian who became successor and pupil to Thales, said that the indefinite (to apeiron) is both principle (archē) and element (stoicheion) of the things that are, and he was the first to introduce this name of the principle. He says that it is neither water nor any other of the so-called elements, but some other indefinite (apeiron) nature, from which come to be all the heavens and the worlds in them; and those things, from which there is coming-to-be for the things that are, are also those into which is their passing-away, in accordance with what must be. For they give penalty (dikê) and recompense to one another for their injustice (adikia) in accordance with the ordering of time—speaking of them in rather poetical terms. It is clear that having seen the change of the four elements into each other, he did not think it fit to make some one of these underlying subject, but something else, apart from these. (Simplicius, Commentary on Aristotle’s Physics 24, lines 13ff. = DK12A9/LM6P5, D6, D12 and DKB1/LM6D6)[1]
Thus, there is an original (and originating) indefinite stuff, from which all the heavens and the worlds in them come to be. This claim probably means that the original state of the universe was an indefinitely large mass of stuff that was also indefinite in its character.[2]Â This stuff then gave rise through its own inherent power to the ingredients that themselves constitute the world as we perceive it.
A testimony about Anaximander from Pseudo-Plutarch (DK12A10/LM6P6, D4) says that “Something productive of hot and cold was separated off from the eternal at the genesis of this world and from this a sphere of flame grew around the air around the earth like the bark around a tree.” Neither the cause nor the precise process of separation is explained, but it is probable that Anaximander would have thought of motion as innate and so that the original source of change was part of the character of the indefinite itself. The passage from Simplicius shows that Anaximander does not think that the eternal indefinite stuff gives rise directly to the cosmos as we know it. Rather, relying on a semi-biological model, Anaximander claims that the apeiron somehow generates the opposites hot and cold. Hot and cold are themselves stuffs with powers; and it is the actions of these stuffs/powers that produce the things that come to be in our world. The opposites act on, dominate, and contain each other, producing a regulated structure; thus things pass away into those things from which they came to be. It is this structured arrangement that Anaximander refers to when he speaks of justice and reparation. Over the course of time, the cycles of the seasons, the rotations of the heavens, and other sorts of cyclical change (including coming-to-be and passing-away) are regulated and thus form a system. This system, ruled by the justice of the ordering of time is in sharp contrast with the chaotic and capricious world of the personified Greek gods who interfere in the workings of the heavens and in the affairs of human beings (Kahn 1985a, Vlastos 1947, Guthrie 1962).
The pattern that can be seen in Thales and Anaximander of an original stuff giving rise to the phenomena of the cosmos continues in the views of the third of the Milesians, Anaximenes. He replaces Anaximander’s apeiron with air, thus eliminating the first stage of the coming-to-be of the cosmos (the something productive of hot and cold). Rather, he returns to an originating stuff more like Thales’ water. In DK13A5/LM7D1 and D7 Aristotle’s associate Theophrastus, quoted by Simplicius, speculates that Anaximenes chose air because he agreed that a basic principle must be neutral (as Anaximander’s apeiron is) but not so lacking in properties that it seems to be nothing at all. Air can apparently take on various properties of color, temperature, humidity, motion, taste, and smell. Moreover, according to Theophrastus, Anaximenes explicitly states the natural mechanism for change; it is the condensation and rarefaction of air that naturally determine the particular characters of the things produced from the originating stuff. Rarified, air becomes fire; more and more condensed, it becomes progressively wind, cloud, water, earth, and finally stones. “The rest,” says Theophrastus, “come to be from these.” Plutarch says that condensation and rarefaction are connected with cooling and heating, and he gives the example of breath (DK13B1/LM7D8,R4). Releasing air from the mouth with compressed lips produces cool air (as in cooling soup by blowing on it), but relaxed lips produce warm air (as when one blows on cold hands to warm them up).
Does the originating stuff persist through the changes that it undergoes in the generating processes? Aristotle’s account suggests that it does, that Anaximenes, for instance, would have thought that stone was really air, although in an altered state, just as we might say that ice is really water, cooled to a point where it goes from a liquid to a solid state. Because the water does not cease to be water when it is cooled and becomes ice, it can return to a liquid when heated and then become a gas when more heat is applied. On this view, the Milesians were material monists, committed to the reality of a single material stuff that undergoes many alterations but persists through the changes (Barnes 1979, Guthrie 1962, Sedley 2007 and 2009). Yet there are reasons to doubt that this was actually the Milesian view. It presumes that the early Greek thinkers anticipated Aristotle’s general theory that change requires enduring underlying substances that gain and lose properties. The earliest Greeks thought more in terms of powers (Vlastos 1947, Heidel 1906), and the metaphysical problem of what it is to be a substance was yet to be formulated. Clearly the Milesians were interested in the originating stuff from which the world developed (Anaximander and Anaximenes are explicit about transformations of such an eternal originating stuff), but the view that this endured as a single substratum may not have been theirs. Rather, it has been suggested by Graham (1997 and 2006; Mourelatos 2008) that the Milesians were not, in Aristotle’s sense, material monists. On this view, the original/originating stuff is transformed into other substances. Anaximenes, for instance, may have thought that the change from air to water does not involve the persistence of air as any sort of substratum. There is no special role that air plays in the theory except that it is the originating stuff and so first in an analysis of the law-like cyclical changes that produce various stuffs as the cosmos develops (Graham 2006, ch. 4). Such an interpretation suggests how different the Milesian conception of the world is from Aristotle’s.
- Xenophanes of Colophon and Heraclitus of Ephesus
Living in the last years of the 6th c. and the beginning of the 5th, Xenophanes and Heraclitus continue the Milesian interest in the nature of the physical world, and both offer cosmological accounts; yet they go further than the Milesians not only through their focus on the human subject and the expanded range of their physical explanations, but by investigating the nature of inquiry itself. Both explore the possibility of human understanding and question its limits. Recent work on Xenophanes’ epistemology and his cosmology has made much of his scientific work clearer and more impressive (Lesher 1992, Mourelatos 2008). He has, to a great extent, been rescued from his traditional status as a minor traveling poet-sage who railed against the glorification of athletes and made some interesting comments about the relativity of human conceptions of the gods. Instead, he has come to be seen as an original thinker in his own right who influenced later philosophers trying to characterize the realms of the human and the divine, and exploring the possibility that human beings can gain genuine knowledge and wisdom, i.e., are able to have a god’s eye view of things and understand them (Curd 2013, Mogyoródi 2002 and 2006).
Xenophanes claims that all meteorological phenomena are clouds, colored, moving, incandescent: rainbow, St. Elmo’s Fire, the sun, the moon. Clouds are fed by exhalations from the land and sea (mixtures of earth and water). The motions of earth and water, and hence of clouds, account for all the things we find around us. His explanations of meteorological and heavenly phenomena lead to a naturalistic science:
She whom they call Iris, this too is by nature (pephuke) cloud
purple, and red, and greeny-yellow to behold. (DK21B32/LM8D39)
Xenophanes says that the star-like phenomena seen when aboard ship, which some call the Dioscuri, are cloudlets, glimmering because of their kind of motion. (DkA39/LM8D38)
In the 1980’s Alexander Mourelatos argued that Xenophanes employs an important new pattern of explanation: X is really Y, where Y reveals the true character of X. Xenophanes signals this by the use of pephuke in DK21B32/LM8D39, and no doubt it (or some word like it) was there in the original of DKA39/LMD36 as well. Xenophanes thus provides an account of a phenomenon often taken to be a sign from the divine—Iris as the messenger; the Dioscuri (St. Elmo’s fire) as comfort for sailors—that reduces it to a natural occurrence.
That meteorological phenomena are not divine is not all that Xenophanes has to say about the gods. He notes anthropomorphic tendencies in conceptions of the gods (DKB14/LMD12: “Mortals suppose that the gods are born, and have their own dress, voice, and body;” DKB16/LMD13: “Ethiopians say that their gods are snub-nosed and dark, Thracians, that theirs are grey-eyed and red-haired”). He also famously suggests that horses, oxen, and lions would have equine, bovine, and leonine gods (DKB15/LM14). Yet Xenophanes also makes positive claims about the nature of the divine, including the claim that there is a single greatest god:
One god greatest among gods and men,
Resembling mortals neither in body nor in thought.
… whole [he] sees, whole [he] thinks, and whole [he] hears,
but completely without toil he agitates all things by the
   thought of his mind.
… always he remains in the same (state), agitated not at all,
nor is it fitting that he come and go to different places at different times. (DK B23, B24, B25, B26 / LM D16, 17, 18, 19)
While indifferent to the affairs of human beings, Xenophanes’ divine being comprehends and controls a cosmos that is infused with thinking: it is understood, organized, and managed by divine intellection. Having removed the gods as bearers of knowledge to humans, and denied that the divine takes an active interest in what mortals can or cannot know, Xenophanes asserts the conclusion to be drawn from his naturalistic interpretation of phenomena: the gods are not going to reveal anything to us; we are epistemologically autonomous and must rely on our own capacity for inquiry. That way, we “discover better,” as he says in DKB18/LMD53, a fragment that is optimistic about the capacities of human intelligence (see Lesher 1991):
Indeed not even from the beginning did the gods indicate all things to mortals, but, in time, inquiring, they discover better.
This suggests that human thought can mimic divine understanding, at least to some degree. Xenophanes’ own practice seems consistent with the claims of DKB18/LMD53; his own inquiries and explanations led him to unified explanations of terrestrial and celestial phenomena. Yet DKB34/LMD49 suggests skepticism:
And of course the clear and certain truth no man has seen,
nor will there be anyone who knows about the gods and what I say about all things;
for even if, in the best case, he should chance to speak what is the case,
all the same, he himself does not know; but opinion is found over all.
Whether this is global or limited skepticism is controversial (Lesher 1992 and 1994 argues for a limited interpretation). Xenophanes stresses the difficulty of coming to certainty, particularly about things beyond our direct experience. Nonetheless, in DKB35/LMD50 (a tantalizingly short fragment), Xenophanes says, “Let these thing be accepted to be like the truth” (see Bryan 2012 for a full discussion).
Famously obscure, accused by Plato of incoherence and by Aristotle of denying the law of non-contradiction, Heraclitus writes in an aphoristic style. His apparently paradoxical claims present difficulties to any interpreter. Nevertheless, he raises important questions about knowledge and the nature of the world. The opening of Heraclitus’ book refers to a “logos which holds forever.”[3] There is disagreement about exactly what Heraclitus meant by using the term logos, but it is clear from DK22B1/LM9D1, D110, and R86 and DKB2/LM9D2 as well as DKB50/LMD46 and other fragments that he refers to an objective law-like principle that governs the cosmos, and which it is possible (but difficult) for humans to come to understand. There is a single order that directs all things (“all things are one” DKB50/LMD46); this order is divine, and is sometimes connected by humans with the traditional gods (it is “both unwilling and willing to be called by the name of Zeus” DKB32/LMD45). Just as Zeus, in the traditional view, controls everything from Olympus with a thunderbolt, so this single ordered system also steers and controls the whole cosmos, but from within. The sign of the unchanging order of the eternal system is fire—just as fire is always changing and always the same, the logos, itself permanent, contains the unchanging account that explains the alterations and transformations of the cosmos.
This plan or order that steers the cosmos is, itself, a rational order. This means not only that it is non-capricious and so intelligible (in the sense that humans can, at least in principle, come to understand it), it is also an intelligent system: there is an intelligent plan at work, if only in the sense of the cosmos working itself out in accordance with rational principles.[4]Â Consider DKB114/LMD105:
Those who would speak with understanding must ground themselves firmly in that which is common to all, just as a city does in its law, and even more firmly! For all human laws are nourished by one law, the divine; for it rules as far at it wishes and suffices for all, and is still more than enough.
Heraclitus is not only claiming that human prescriptive law must harmonize with divine law, but he is also asserting that divine law encompasses both the universal laws of the cosmos itself and the particular laws of humans. The cosmos itself is an intelligent, eternal (and hence divine) system that orders and regulates itself in an intelligent way: the logos is the account of this self-regulation. We can come to grasp and understand at least part of this divine system. This is not merely because we ourselves are part of (contained in) the system, but because we have, through our capacity for intelligent thinking, the power to grasp the system as a whole, through knowing the logos. How this grasping is supposed to work is tantalizingly obscure.
Heraclitus regards the cosmos as an ordered system like a language that can be read or heard and understood by those who are attuned to it. That language is not just the physical evidence around us (“Eyes and ears are bad witnesses to those with barbarian souls” DKB107/LMD33); the sheer accumulation of information is not the same as wisdom (see the rebuke in DK22B40/LMD20, quoted above). Although the evidence of the senses is important (see DKB55/LMD31), careful and thoughtful inquiry is also necessary. Those who are lovers of wisdom must be good inquirers into many things (DKB35/LMD40; also DKB101/LM36: “I enquired into myself”) and must be able to grasp how the phenomena are signs or evidence of the larger order; as Heraclitus notes in DKB123/LMD35, “nature is accustomed to hide itself,” and the evidence must be interpreted carefully. That evidence is the interplay of opposing states and forces, which Heraclitus points to by claims about the unity of opposites and the roles of strife in human life as well as in the cosmos. There are fragments that proclaim the unity or identity of opposites: the road up and down are one and the same (DKB60/LMD51), the path of writing is both straight and crooked (DKB59/LMD52), sea water is very pure and very foul (DKB61/LMD78). The famous river fragments (DKB49a/LMR9; DKB12/LMD65a, D102; DKB91a not in LM) question the identity of things over time, while a number of fragments point to the relativity of value judgments (DKB9, B82, B102 / LM D79, D81, D73). Anaximander’s orderly arrangement of just reciprocity governed by time is replaced by a system ruled by what Heraclitus calls war: “It is right to know that war is common and justice strife, and that all things come to be through strife and are so ordained” (DKB80/LMD63). This strife or war is the set of changes and alterations that constitute the processes of the cosmos. These changes are regular and capable of being understood by one who can speak the language of the logos and thus interpret it properly (see Long 2009). Although the evidence is confusing, it points to the deeper regularities that constitute the cosmos, just as Heraclitus’ own remarks can seem obscure yet point to the truth. Heraclitus surely has his own message (and his delivery of it) in mind in DKB93/LM41, “The lord whose oracle is at Delphi neither speaks nor conceals, but gives a sign.”
One of the earliest of the Greek philosophers to discuss the human soul, He