Presocratic Contributions to the Theory of Knowledge

© 1998 J. H. Lesher

[This paper represents further development of some of the ideas contained in an article, ‘Early Interest in Knowledge’ scheduled to appear in The Cambridge Companion to Early Greek Philosophy (Cambridge University Press, forthcoming). I am grateful to the editor of the Cambridge Companion volume, Professor A. A. Long, for permission to include selected portions of that article in the present paper.]

Some years ago I published a study of the passage in Plato’s Theaetetus known as Socrates’ ‘Dream Theory of Knowledge’1. In that paper I argued that Socrates’ dream theory posed difficulties for a view of knowledge Plato had presented--evidently as problem free--in a number of earlier dialogues. On that earlier view, a necessary condition for knowing, as opposed to merely believing truly, was being able to present some kind of logos or rational account--typically of a thing’s nature or ‘what it is’. But here in the Theaetetus, according to the new theory Socrates claims came to him in a dream, there can be no logos of ‘those simple elements of which we and all other things are composed’, although they can be perceived. And because nothing lacking a logos can be known, there can be no knowledge of any simple element. But since a logos can be given of any complex entity--at a minimum, simply by listing its component parts--complexes are still knowable. In short, according to the theory, there is a basic asymmetry to knowledge--complex objects can be known, but simple ones cannot.

In the discussion which follows the statement of this theory, Socrates attacks the asymmetry thesis by arguing that if elements are unknown, then so also must be the complexes composed of them. Taking as a test case for the theory the letters and syllables of the alphabet, he claims that it would be absurd for someone to be said to know the first syllable of his name, ‘SO’ while being entirely ignorant of the letters ‘S’ and ‘O’. And at Theaetetus 206b he again invokes our experience of learning the letters of the alphabet to argue that the dream theory has it precisely backwards: simples are, if anything more knowable than the complexes composed of them:

So if we are to argue from our own experience of elements and complexes [i.e. the letters and syllables of the alphabet] to other cases, we shall conclude that elements in general yield knowledge that is much clearer than that of the complex, and more effective for a complete grasp of anything we seek to learn. And if anyone tells us that the complex is by its nature knowable while the element is unknowable we shall suppose that, whether he intends it or not, he is playing with us.

As I read the passage, then, Plato had presented and then proceeded to refute the dream theory in order to suggest that in addition to having the kind of knowledge that involves possessing a logos, we must also be able to know realities in and through perceiving them. In Russell’s terms, we must have some knowledge by acquaintance of the elements, as well as knowledge by description.

This way of reading this portion of the Theaetetus has gained some supporters over the years. But, however others may feel about it, I no longer find it very convincing. For one thing, much of Plato’s dialogue is devoted to showing why sense perception is inadequate to the requirements for knowledge--it can reach neither truth nor reality. If Plato had here been urging us to regard perceptual awareness of an object as a second, equally respectable kind of knowledge he would have been moving in a direction directly contrary to the main drift of his dialogue as a whole. In addition, in the dialogues following the Theaetetus Plato will argue that in at least one respect it is possible to have a logos-based knowledge of simple elements--in so far as we can discover the principles which govern their possible permutations and combinations. Just as the expert grammarian who ‘knows his letters’ has learned which individual letters can be combined with which to form syllables, so we master the basic elements of reality when we learn which can be combined with which to form larger entities. So even if the simple elements were completely unknowable, when considered in isolation from one another, they could still be known in virtue of their relationships with one another, and to the larger complex entity. Thus, even if we were to agree that Socrates’ argument against the dream theory pointed up a need for some knowledge of the basic elements, this would not call for acknowledging the existence of some perceptually-based form of knowledge.

Even more worrisome to me than these considerations was the feeling I began to have that Plato’s epistemological reflections must have taken place in some intellectual setting--of which I was entirely ignorant. I felt very much like someone who had come in on the tail end of a conversation, or begun to read a book at the start of its final chapter. So I decided, to borrow the title of a famous paper by Karl Popper, to go ‘back to the presocratics’2, to undertake to read whatever epistemological accounts had been presented by the philosophers who lived before and during the time of Socrates, to try to see how the epistemological issues explored in the Theaetetus had entered into philosophical debate.

It then came as something of a shock to me to learn that in the view of many scholars, there were no such accounts to be read. As David Hamlyn put this thesis:

The interests of these philosophers [viz. the presocratics] were purely physiological or physical in character. They made no attempt to philosophize about the nature of the concept of sense perception, nor in general did they raise epistemological issues.3

The more widely I read, though, the less credible Hamlyn’s thesis became. There were at least individual fragments of the writings of Xenophanes, Heraclitus, Parmenides, and other early thinkers, that seem to be concerned, however briefly and obscurely, with the conditions under which human beings acquire and possess knowledge. If none of those pronouncements measured up to anything so grand as ‘a theory of knowledge’ there were still a number of individual nuggets deserving to be mined.

I then encountered the writings of one group of scholars--the distinguished classicists Bruno Snell, Hermann Fränkel, and Kurt von Fritz--who had regarded presocratic views of knowledge as rich in intellectual interest and importance. In a series of well known and influential studies, the ‘developmentalists’ as I came to think of them, argued that the presocratics were the first to conceive of knowledge, to put it briefly, as an intellectual achievement. As they explained the process, in the earliest Greek literature, the Homeric poems, ‘knowing’ had essentially been synonymous with ‘seeing’ or ‘having seen’, and something of this naive or common sense view of knowledge could be seen in the writings of earliest Ionian philosophers (as well as in the preference expressed by the Ionian historian Herodotus for ‘eye-witness’ accounts). In this respect, as Snell was the first to argue, the ancient Greeks were still under the influence of an ancient association of ‘knowing’ with ‘seeing’ which went back to the earliest period of Indo-European civilization (our English words ‘wisdom’ and ‘wits’, like the German verb wissen, all derive from the same Indo-European root, *weid-, meaning ‘see’). Parmenides was the first, so the developmentalists argued, to claim that knowledge, or knowledge properly speaking, comes to us not through our senses, but through thought or reflection. And with Parmenides, they claimed, Greek thought arrived at the conception of nous or ‘intellectual insight’; i.e. of a distinctly intellectual grasp of the truth.4

It was no accident that the developmentalists’ account of early Greek thinking about knowledge emerged from within the tradition of 19th-century German idealism. Snell’s landmark 1924 study of the Greek expressions for knowledge began with a quotation from von Humbolt which proclaimed that a rise in the consciousness of a people goes hand in hand with an evolution in their forms of speech--both are manifestations of their national Geist or spirit. The development of a distinctly intellectual conception of knowledge by the early Greek philosophers, along with a new set of expressions to characterize it, was exactly the kind of advance in consciousness that Hegel’s Phenomenology of Mind had claimed had been taking place throughout world history.

But as I began to think about it, the ‘developmental’ account began to seem almost as dubious as Hegel’s belief in the workings of a universal Geist. ‘Knowing’ in the Homeric epics, for one thing, did not imply ‘having seen’ As is clear from Aeneas’ remarks to Achilles in Book XX of the Iliad:

We know each other’s lineage and parents, because we have heard the tales told in ancient days by mortal men, but not with sight of eyes have you seen my parents nor I yours. (203-04)

In both poems, Homer describes the characters of his stories as coming to know not only on the basis of what they have seen for themselves but also through the reports or testimony of others, or through instruction by recognized experts and respected authorities, including on many occasions, the gods themselves.5 And if seeing was not entirely necessary for Homeric knowledge, neither was it sufficient either. The drama of the Odyssey rests in part on the fact that not every figure who arrives on the scene is thereby immediately recognized as who he or she really is, and not every situation is immediately understood.6  It is true, and important to note, that Parmenides was the first presocratic thinker to ground his claims in philosophical argumentation, but both Homer and Parmenides characterize the attainment of knowledge in terms of the same two hallmarks--the disclosure of a reliable indicator of the truth, and the attainment of complete conviction or persuasion.7  So while the ‘developmentalists’ may have identified some items of philosophical interest in presocratic remarks on the topic of knowledge, it seemed to me that their account of the evolution in the meaning of early Greek expressions for knowledge was badly flawed.

In the process of working through these issues, though, I began to develop an appreciation for the novelty represented by a number of presocratic observations on human knowledge. In what follows I try to identify some of the most influential of these, based on what is known of the teachings of Xenophanes, Heraclitus, and Parmenides.

(1) Xenophanes of Colophon was a traveling poet and civic counselor who lived in various parts of the ancient Greek world during the late 6th and early 5th centuries BC. One of his poetic creations (Fr. 34) comments on how much any human being can hope to know:

And indeed there has been no man, nor will there be, who knows the certain truth (to saphes)
About the gods and such things as I say concerning all things.
For even if one were to do better than others in speaking of what comes to pass
Still he himself would not know (ouk oide); but opinion (dokos) is allotted to all.

Many divergent interpretations of these remarks have been offered. I will mention the two most widely held views before offering one of my own.

Sextus Empiricus, to whom we are indebted for quoting and thereby preserving these remarks for posterity, regarded Xenophanes as fledgling advocate of his own position--philosophical scepticism. Despite the fact that in other poems Xenophanes dogmatically affirms the existence of ‘one greatest god’ who ‘sees, thinks, and hears as a whole’, and ‘moves all things by the thought of his mind alone’, here in 34, Sextus argues, Xenophanes anticipates the sceptical thesis that nothing whatsoever can be known since there is no criterion the application of which can convert mere conjecture into the certain truth.8

Doubts about Xenophanes as proto-sceptic were expressed as early as Diogenes Laertius, and most modern authorities regard Sextus’ reading of 34 as anachronistic. For one thing, the reference in line three to ‘the gods and . . . all things’ suggests that ‘all things’ did not mean ‘all possible subjects’ as Sextus takes it, for if it had, there would have be no need to mention ‘the gods’ as well. Xenophanes’ concern, moreover, is not the certain truth about ‘all things’ but rather about ‘such things as I say about all things’. As is clear from the fragments which present his scientific views (e.g. that ‘all things come from the earth, or from earth and water’), ‘all things’ here almost certainly means ‘all constituents of the natural realm’, rather than ‘all possible subjects’. It is also difficult to see how the imperative in Xenophanes’ Fr.35:

...let these things be believed, certainly, as like the realities...

could possibly be reconciled with the ancient sceptic’s pursuit of indifference, i.e. reaching the state of mind in which no proposition seems any more deserving of belief than its denial. So 34 was probably not the founding document of ancient scepticism.

The similarity between Xenophanes’ view of the supreme being as ‘one’ and unmoving’ and Parmenides’ view of what exists as ‘one in form’ and ‘motionless’ led some later writers to conclude that Fr. 34 must have been motivated by the same rationalist conception of knowledge championed by Parmenides.9  No human being knows the certain truth, in short, because our sense faculties represent a wholly unreliable source of information.

In other fragments, however, and in many of the views attributed to him by ancient commentators, Xenophanes appears to assume that the senses can be relied upon to give us a valid view of the nature of things. His Fr. 38, for example, includes the remark that:

The upper limit of the earth is seen (oratai) here at our feet. . .

and other fragments and testimonia refer to a wide range of observed phenomena--to the presence of water in underground caverns, month-long ‘eclipses’ of the sun (perhaps the annual disappearance of the sun in northern latitudes), volcanic eruptions in Sicily, the freak electrical phenomenon known as ‘St. Elmo’s fire’, differing social customs, and divergent conceptions of the gods held by peoples from Thrace to Ethiopia.

In one especially revealing couplet, Xenophanes contrasts the popular view of Iris--the famous rainbow-messenger goddess of Greek popular religion--with the meteorological phenomenon that is there ‘to behold’, or ‘look at’ (Fr. 32):

And she whom they call Iris, this too is a cloud by nature,
Purple, red, and greenish-yellow to look at.

Xenophanes proposes that Iris--the rainbow, is properly described and understood not in terms of its traditional name and attendant mythic significance, but rather as a natural phenomenon--as ‘a cloud, purple, red, and greenish-yellow to look at.’ He offers similar cloud or moisture-based explanations for the sun, moon, stars, and a host of other phenomena long regarded either as super-natural beings or instruments of the divine will. So Xenophanes appears not only to accept as valid information supplied by our senses but to be urging his audience to consider how they might make better use of their faculties to understand the nature of the world around them. Xenophanes, then, was no Eleatic rationalist either.

Since Fr. 34 begins with the phrase ‘and indeed...’ it is entirely possible that we do not have the whole of the argument, but two general considerations are relevant: (1) Given the sharp contrast between divine and mortal capacities Xenophanes draws elsewhere in his poems, we can be confident that he believed that no mortal being could achieve a god-like, synoptic view of ‘all things’; and (2) Given the association of what is saphes or ‘clear and certain’ with what can be directly observed--both Herodotus (at II, 44) and Xenophanes’ contemporary Alcmaeon (in Fr. 1) use the term in just this way--the impossibility of first-hand experience of the gods and ‘all things’ would rule out any possibility of knowing to saphes, or ‘the clear and certain truth’ about them. The message here would be that in so far as the propositions which make up the body of scientific thinking are universal--they assert what is the case everywhere and for all time--they can never be known with complete certainty by any mortal being. The first generation of Ionian scientists--Thales, Anaximander, and Anaximenes--may have been right to champion historia--or inquiry in the form of wide travel and direct observation, but the most important truths--those that relate to the nature of the divine and the basic forces in nature--can never be discovered in this manner. The hypothetical line of argument in lines three and four can be seen as reinforcing this cautionary sentiment--perhaps with an implicit reference to self-styled paragons of wisdom such as Epimenides and Pythagoras. The point would be that no one (moreover) ought to be credited with such knowledge simply on the basis of describing, perhaps even successfully predicting, individual events as they take place.

Xenophanes’ famous critique of religious belief--that human beings tend to paint the gods in their own image--is also relevant to this thesis. Fr. 16 states that:

Ethiopians say their gods are snub-nosed and black;
Thracians that theirs are blue-eyed and blond-haired.

--and Fr. 15 adds that if horses and cows had hands and could paint pictures their gods would look like horses and cows. The choice of Ethiopians and Thracians--as the southernmost and northernmost peoples known to exist, is probably significant: if every religious believer--everyone, that is, from ‘pole to pole’--paints the gods in their own form-- then no mortal should ever expect to obtain a clear, un-mediated view of the divine nature. Xenophanes denies knowledge, not so much to make room for faith, but rather for true opinion. But in distinguishing knowledge from true opinion he responded to the accounts of ‘all things’ put forward by his Milesian predecessors in the same critical spirit in which Kant responded to the claims of traditional metaphysics: where there is no possibility of experience, there can be no prospect of knowledge either.

(2) Heraclitus of Ephesus was a compatriot and close contemporary of Xenophanes, and the author of a number of famous aphorisms about life, the soul, and the nature of things in general. Although he has often been described as a profound thinker there is little agreement about what his profound thought is supposed to have been. According to Plato and the later doxographical tradition Heraclitus was the author of the doctrine of universal flux--that ‘everything flows’ or constantly changes. Recent scholarly work, I think, has largely undermined this interpretation.10 According to Aristotle, Heraclitus championed the odd thesis that the same thing could both be and not be at the same time and in the same respect--and so opposed the Law of Non-Contradiction. But this also goes well beyond anything Heraclitus ever said. More recently, Heraclitus has been credited with a novel metaphysics organized around processes rather than material substances or stuffs.

But one indisputably Heraclitean thesis was that all events, things, and processes in nature must be understood in connection with the logos, a term defined by Kirk, Raven, and Schofield as:

...the unifying formula or proportionate method of arrangement of things, what might almost be called their structural plan, both individual and in sum.11

In various ways Heraclitus makes it clear that at least one key feature of nature’s ‘structural plan’ is ‘the hidden unity of opposites’--the way in which many if not all natural phenomena embody or in some way relate to an internal ‘tension’ or ‘strife’ among opposite qualities and forces, a conflict symbolized, perhaps also epitomized, by fire. Under the general heading of ‘unity in opposition’ Heraclitus makes a number of related points: (1) that things that are ‘the same’ can also be ‘different’--e.g. that one and the same road can be both the road down and the road up--depending on the direction one is headed, or that seawater can be both pure and polluted--depending on whether it is fish or people who are drinking it; or that the ‘same’ river contains ever changing waters, etc.; (2) that things that are ‘different’ can also be ‘the same’--e.g. that classic opposites like day and night, high and low notes, and male and female can also be understood as closely linked with one another, both conceptually and as physical phenomena; and (3) that many entities work to sustain the existence and proper functioning of their opposite numbers--e.g. that ‘disease makes health pleasant and good, as hunger does satiety, and weariness does rest’ (Fr. 111). Because tension or conflict between the opposites is seen as a positive, creative force at work throughout the cosmos Heraclitus concludes that ‘war is father and king of all’ and that ‘all things happen by strife and necessity’ (Fr. 80). One might want to argue about how deep this insight really is, and about whether it is philosophical useful for Heraclitus to lump together so many different kinds of relationships under a single heading, but there can be no doubt that ‘unity in opposition’ was one of Heraclitus’ basic doctrines.

What I think was more useful philosophically are some remarks Heraclitus made about how this structural unity would have to be discovered. He tells us, for example, that even paragons of wisdom, those acknowledged to have learned ‘many things’ have failed to discover it (Fr. 40):

The learning of many things does not teach understanding (noos); or else it would have taught Hesiod and Pythagoras, and again Xenophanes and Hecataeus.

The mention of Xenophanes and the Milesian geographer Hecataeus--both exponents of historia--inquiry in the form of fact-finding travel and direct observation--suggests that no amount of inquiry along those lines can bring one to a proper appreciation of the logos. As Fr. 1 reports, ‘even men of experience are like men of no experience’ when it comes to grasping the logos:

For although all things happen according to the logos people are like those with no experience even when they experience such words and deeds as I explain, when I distinguish each thing according to its nature (phusin) and make known how it is.

The inclusion of Hesiod and Pythagoras would suggest that poets and seers who claim to have gained truth from divine sources have done no better than those who travel about the world observing things for themselves.

Fr. 107 reinforces the point that a proper understanding of the real nature of things cannot be extracted from the information supplied by the senses:

Bad witnesses are eyes and ears of those having barbarian souls.

i.e. our faculties of sense provide false or misleading testimony to those not already attuned to the hidden principle of unity. We are never told precisely how the senses can easily mislead the unknowing, but my guess would be that the senses highlight differences or contrasts in things. In strictly sensory terms no two things can be more different, more ‘at opposite ends of the spectrum’ than light and dark--or as we say, ‘as different as night and day’. So if our task is to discover how things that differ can also be the same, we need to move beyond sensory content, and into the realm of thought and reflection.

One common view of the nature of thought, expressed often in archaic Greek poetry, was that mortals ‘think such things as they meet with’--i.e. their thoughts reflect only their own (extremely limited) personal circumstances.12 Heraclitus turns this sentiment on its head when he complains (Fr. 17):

The many do not think such things as they meet with, nor, having learned, do they know, though each thinks they have.

Through these juxtapositions of opposing pairs of qualities--experienced but still inexperienced, having heard the word but not gotten the message, being in contact but still isolated, and being awake but still asleep-- Heraclitus seems to have been trying to provoke his audience into some appreciation for the possibility that their usual sources of information may have failed them in some crucial respects, and that what they regard as knowledge is really only a kind of ignorance.

But if neither the ‘much learning’ of the sages nor the ‘much experience’ provided by eyes and ears can ‘teach understanding’, what can?

One instructive simile is provided by Fr. 51:

They do not understand (xuniasin) how, while differing from itself, it is in agreement with itself. There is a back-stretched connection, like that of a bow or lyre.

Grasping the nature of the ‘back-stretched connection’ in the case of the bow and lyre presumably requires coming to understand (Heraclitus’ term here and often elsewhere is xunienai-- ‘to come together with’ or ‘understand’13) how each of the physical parts--the string and wooden frame--contributes to the effective operation of the whole, either the whole weapon or the whole musical instrument. The string must be pulled taut against the frame in order for either device to function properly--where there is no antecedent tension, there can be no subsequent action either. At least part of his message here is that we must go through the same processes of analysis and synthesis if we are to understand how the logos is at work in the cosmos as a whole. In general, then, understanding how ‘things that differ’ are also ‘in agreement’ requires mastering the principles of ‘unity in opposition’ just mentioned--understanding how each of two opposing qualities has a place and role within a single larger entity; conversely, how one entity can happily accommodate two qualities fiercely opposed to one another; and how bitter enemies can also mutually support and sustain one another’s existence and operation.

In these remarks about how the basic unifying principle must be discovered, Heraclitus has moved some distance away from popular conception of human wisdom as embodied in the teachings of poets and sages, away also from the Ionian scientists’ view of knowledge as the natural by-product of travel and direct observation, and toward a view of knowledge as a theoretical grasp or understanding of the phusis or nature of a thing achieved, only with some effort and difficulty, through reflection.

In addition, as Gregory Vlastos has noted,14 Heraclitus Fr. 1 marks the appearance of one of the most important ideas in presocratic thought--that of the phusis or ‘nature’ of a thing. When used with reference to individual phenomena, as here in Fr. 1. phusis designates:

. . . that cluster of stable characteristics by which we can recognize a thing and anticipate the limits within which it can act upon other things or be acted upon by them.

And when used in connection with the cosmos as a whole, phusis supplies a framework for thinking about nature in its entirety, as a single entity from which all existing things originally came into being, or as a basic element or set of elements which represent, at bottom, what all things really were.

The frequency with which early Greek philosophers used the term is probably what led Aristotle to refer to them not as ‘presocratics’, but as phusiologoi--’those who give an account of nature’, and the phusis of a thing continued to be a major focus of philosophical interest in the classical period. The Socrates who appears in Plato’s dialogues holds that we must first discover the essential nature of a thing--its ti esti or ‘what it is’--before attempting to determine what other features it might possess. And both Plato and Aristotle will characterize knowledge in the most basic sense of the term as grasping in thought the essence or the ‘what it is to be’ of a thing. This linkage of knowledge with the nature or ‘what’ of a thing helps to explain the frequency with which the ability to give some sort of logos enters into ancient definitions of knowledge, since being able to give some sort of account of a thing’s nature is quite plausibly regarded as a necessary condition for being said to know what it is. In general, when an ancient Greek thinker offers a theory of knowledge, it is not knowledge in general or per se whose nature is under consideration, but rather the special knowledge of a thing’s essence or essential nature, and Heraclitus is the first, so far as we know, to shape philosophical inquiry in this way.

(3) At some point in the early decades of the 5th century BC Parmenides of Elea composed an extraordinary poem which transformed the character of Greek philosophy, and of much philosophy ever since. While there are many obscure features in his poem, and rival interpretations abound, there is general agreement on four basic points. First, Parmenides’ account of the nature of to eon--‘the existing thing’ or ‘what exists’, raised the discussion to a much higher level of abstraction. After Parmenides, one could still seek to identify the material substance of which all things were composed, but it was now necessary to show that the particular substance one selected satisfied each of the conditions identified by Parmenides as essential to any existing thing. Second, Parmenides is the first Greek philosopher (that we know of) to construct a series of arguments, often quite complex and subtle ones, in defense of his main claims. He does so by first organizing a critical review (an elenchos or ‘testing’) of the four possible ways of speaking and thinking about any subject--that it is, that it is not, that it either is or is not, and that it both is and is not--and argues that only the ‘it is’ way ‘attends upon’ or is connected with Truth. He then supports his ‘it is’ choice by arguing that whatever exists must exist eternally, uniformly, and fully in every possible respect, and these conclusions follow directly from the rejections of the possibility of generation and destruction, divisibility, motion, and change. Third, it is agreed that Parmenides asserted some important connection between thought and reality. ‘The same thing’, he says in Fr. 3 ‘exists for thinking and for being’, or as some read it, ‘Thinking is the same as being’. As this is usually understood, Parmenides held that all meaningful thought and discourse must have reality as its object--that one cannot meaningfully talk, think, or know of or about non-existent things. And, fourth, after having dismissed as unintelligible all talk about generation, destruction, motion, and change, Parmenides appears to contradict himself by presenting an account, called ‘the way of opinion’ which accepts the reality of generation, destruction, motion, and change. Here I must ignore many of these puzzles and offer only a few comments about the conception of knowledge which figures in Parmenides’ story, and how it shaped later accounts.

Parmenides never tells us in so many words what he thinks it means to know, or to have knowledge, but several fragments provide helpful clues. In Fr. 1 he describes a trip taken at some point in the past by a youth--presumably himself--to a distant realm, the home of a goddess who appears to be something like the patron saint of knowledge--she is described as the one who ‘leads the knowing man through every town’.15 When she greets the youth, the goddess assures him that: is proper that you should learn all things,
Both an unshaking (atremes) heart of very persuasive truth
as well as mortal beliefs in which there is no true trust.

The related ideas of ‘persuasion’ and ‘trust’ appear frequently throughout the poem: the ‘it is’ way of speaking and thinking is identified as ‘the path of persuasion because it attends upon Truth’; the ‘strength of trust’ will not allow anything to come to be from ‘what is not’; and coming-to-be and perishing are both said to be driven off by ‘true trust’. It would appear that the youth learns the ‘unshaking’ or ‘steadfast heart of very persuasive truth’ promised to him by the goddess by being led through all the possible ways of speaking and thinking about what exists, eliminating all but the ‘it is’ way, and then working his way through the series of proofs in Fr. 8 designed to establish that what exists must be eternal, uniform, and unchanging in every possible respect.

A contrast of steadfast understanding with ‘unsteady’ or ‘wandering’ mortal opinion is one of the poem’s main leitmotifs. It appears in the goddess’s injunction in Fr. 4 to:

Look upon things which, though far off, are steadily (bebaiôs) present to the mind,
For you shall not cut off what is from holding fast to what is.

and in her indictment of mortal opinion in Fr. 6:

[I restrain you]...Then also from this way, on which mortals knowing nothing
Wander, two-headed, for helplessness in their breast
guides their wandering mind

In Fr. 7 the ‘is not’ way of thinking, described as born of much experience, is again contrasted with the understanding provided by the goddess’s logos:

Nor let habit born of much experience force you down this way
Plying an aimless eye and echoing ear and tongue,
But judge by means of logos the much-contested testing spoken by me.

The problem with sight and hearing as suggested by the epithets ‘aimless’ and ‘echoing’, are their fuzziness and inconstancy. As Gwil Owen explained this point, our faculties of sight and hearing lead us to think that things can exist in various locations, or at various times, change location, and develop new qualities over time.16 According to the goddess’s logos , however, the only defensible view of what exists is that it must be eternal, entirely uniform, motionless and unchanging, and fully developed at every moment (Fr. 8):

Still single remains the story of a way: that it is. And on it are very many signs (sêmata)
That since it is, it is uncreated and imperishable,
Whole, of a single kind, unshaking (atremes) and complete.

In short, Parmenides presents himself as having risen above the level of ‘know-nothing mortals’ and their inconstant beliefs by acquiring an ‘unshaking heart of very persuasive truth’ about what exists. He acquires those unshakable convictions through an exhaustive critical review of the possible ways of speaking and thinking, and by uncovering of a set of proofs or ‘signs’ that whatever exists must do so eternally, uniformly, and unalterably in every possible respect.

Two features of Parmenides’ characterization of his knowledge merit comment: (1) the view expressed by the goddess that the youth will achieve knowledge about what exists by acquiring or ‘learning’ an ‘atremes heart’ or ‘unshaking conviction’; and (2) that the atremes character of that conviction is grounded in the atremes nature of what exists. As Fr. 4 makes clear, the abiding character of what exists does more than parallel our firm conviction, it is the singularly necessary and sufficient condition for achieving that state of awareness: ‘what is’ is ‘steadily present to our mind’ because it is not possible for any part of what exists to be separated from any other part--because (or ‘for’: Greek gar) ‘what is’ ‘clings close’ to what is. Hence, if we are to achieve the kind of unwavering conviction we are required to have in order to know what there is, we have no option but to turn our thoughts away from the inconstant world presented to us in sense experience and focus our thoughts instead on the only kind of reality that can never let us down.

A century after Parmenides, Plato will present what is many respects a commentary on Parmenides’ understanding of the conditions of knowledge when he argues at Timaeus 51e-52a that the very possibility of gaining knowledge stands or falls with the existence of eternal and changeless objects--in Plato’s case, the Forms or Ideas:

If knowledge and true opinion are two distinct kinds, then I say there certainly are these self-existent ideas un-perceived by sense, and apprehended only by the mind...But we must affirm them to be distinct kinds, for they have a different origin and are of a different nature... the one is always accompanied by a true logos, the other is without a logos; the one cannot be overcome by persuasion, but the other can...So we must acknowledge that one kind of being is the form which is always the same, uncreated and indestructible... and imperceptible by sense, and of which the contemplation is granted only to thought.

Both parts of this Platonic-Parmenidean thesis are, of course, subject to criticism. The view that only someone who has achieved complete conviction or confidence about some matter can be credited with knowledge arguably confuses complete conviction with complete justification. To take one well-known example--the case of an ‘unconfident student’--we can imagine how someone might be able to demonstrate through repeated successful performance that he or she is knowledgeable about some topic, but still feels some degree of uncertainty about whether they do so or not. Whatever might be the case with respect to the Greek expressions for knowledge, it seems natural for us to say that in a case of this sort the student does know the subject matter, but--for some reason--lacks the appropriate degree of self-confidence to be prepared to claim to know.

Nor is it clear why being completely persuaded on rational grounds of the truth of some proposition guarantees that one will never be shaken out of that conviction at some future date. I have to believe, for example, that there are many things I once knew--perhaps many, many things-- about which I no longer have any firm convictions. I feel sure, for example, that I used to know sines from cosines and cosines from tangents, but I no longer do, and I would probably believe anything you told me on the topic. And, finally, the connection between firm conviction and unalterable reality is arguably not as close as Parmenides and Plato seemed to think. The fact that some object is constantly changing does not preclude the possibility of being able to think or say something about it with complete confidence--at the very least, we could confidently believe that the object before us is constantly changing, and we might be able to confidently affirm a number of claims appropriately qualified as to places and times.17 But, however one resolves these questions, there can be no doubting that Parmenides’ conception of knowledge as an unshakable grasp of an unchanging reality profoundly shaped Plato’s thinking about the conditions of knowledge, and through Plato’s enormous influence, much of Western philosophy ever since.


1. ‘Gnôsis and Epistêmê in Socrates’ Dream in the Theaetetus,’ Journal of Hellenic Studies, Vol. 84 (l969), pp. 72-78. [Jump back to text.]

2. K.R. Popper, ‘Back to the Presocratics’ in Conjectures and Refutations, 3rd ed. (London, 1956). [Jump back to text.]

3. D.W. Hamlyn, Sensation and Perception (London, 1961), p.8. [Jump back to text.]

4. Bruno Snell, Die Ausdrücke für den Begriff des Wissens in der vorplatonischen Philosophie (Philologische Untersuchungen 29; Berlin, 1924); see also his Discovery of the Mind: The Greek Origins of European Thought (Harper and Row: New York and Evanston, 1960), an English translation by T. G. Rosenmeyer of the 2nd edition of Die Entdeckung des Geistes (Hamburg, 1948), with a chapter added on ‘Human Knowledge and Divine Knowledge’; and ‘Wie die Griechen lernten was geistige Tätigkeit ist,’ in The Journal of Hellenic Studies, Vol. 93 (1973), pp. 172-84; reprinted in Der Weg zum Denken und zur Wahrheit (Hypomnemata 57, Göttingen, 1978); Kurt von Fritz, ‘Noeô, Noein, and Their Derivatives in Pre-Socratic Philosophy (Excluding Anaxagoras),’ Classical Philology, Vol. 40 (1945), pp. 223-42 and Vol. 41 (1946), pp. 12-34, reprinted in A.P.D. Mourelatos, ed. The Pre-Socratics: A Collection of Critical Essays (Anchor/Doubleday: Garden City, New York, 1974); and Herman Fränkel, Dichtung und Philosophie des frühen Griechentums (Munich, 1962), English trans. by M. Hadas and J. Willis, Early Greek Poetry and Philosophy (New York and London, 1973); and ‘Xenophanesstudien’, Hermes, Vol. 60 (1925), pp. 174-92; reprinted in his Wege und Formen frügriechischen Denkens (Munich, 1960); a portion of this study was translated into English by Cosgrove and Mourelatos and included in the latter’s The Pre-Socratics as ‘Xenophanes’ Empiricism and His Critique of Knowledge’, pp. 118-31. Many of the views advanced in these studies were subsequently incorporated in accounts given by Guthrie, Kahn, Mourelatos, and Robinson, to mention only a few. [Jump back to text.]

5. The words that afford Aeneas his knowledge, for example, are more than just ‘reports’ or ‘things heard from others’ (kluta), they are prokluta, ‘vintage tales’, which carried the authority of ancient tradition. Similarly, Aegisthus is said to know (eidôs) his fate because the gods ‘spoke to him, sending keen-sighted Hermes’ (Od. I, 38); Echenor the Corinthian learns of his fate from the expert seer Polyidus (Il. XIII, 666); and Odysseus learns what the future holds for him through the words of the ghost of the seer Teiresias at Od. XI, 100 ff. Other examples of hearing-based knowledge can be found at Il. I, 362; VI, 150; XIII, 665; XVIII, 52-53; XXII, 437-39; Od. I, 37, 174; IV, 645; IX, 15-16; XII, 156; XIII, 232. [Jump back to text.]

6. For a defense of this claim see my ‘Perceiving and Knowing in the Iliad and Odyssey,’ Phronesis, Vol. 26 (l98l), pp. 2-24. [Jump back to text.]

7. For the details, see my discussion of ‘the Parmenidean Way of Knowing’ in ‘The Emergence of Philosophical Interest in Cognition,’ Oxford Studies in Ancient Philosophy, Vol. 12 (1994), pp. 1-34. [Jump back to text.]

8. Against the Professors VII, 49. [Jump back to text.]

9. See the ancient testimonia by Aëtius and Aristotles in A 49 in Diels and Kranz, Die Fragmente der Vorsokratiker, 6th ed. (Berlin, 1951); English translations of the Xenophanes testimonia are given in my Xenophanes of Colophon: Fragments (Toronto, 1992). Among modern writers, the rationalist reading has been defended by Gigon, Deichgräber, and Finkelberg (for the details on these a number of other interpretations of Fr. 34 see Xenophanes, pp. 155-69. [Jump back to text.]

10. See G.S. Kirk, Heraclitus, the Cosmic Fragments (Cambridge, 1954). [Jump back to text.]

11. Kirk, Raven, and Schofield, The Presocratic Philosophers (Cambridge, 1983), p. 187. [Jump back to text.]

12. Cf. Archilochus, Fr. 70: ‘Of such a sort, Glaucus, is the consciousness (thymos) of mortal man, whatever Zeus may bring him for the day, for he thinks such things as he meets with.’ Cf. also Semonides, fr.1; Theognis, 141-42; Solon, frs. 1, 13, 16; Pindar, Olympian VII.25-26; Nemean VI.6-7; VII.23-24; XI.43-47, etc. [Jump back to text.]

13. For an explanation of the full resonance of this term in the Heraclitus fragments, see ‘Heraclitus’ Epistemological Vocabulary,’ Hermes, Vol. 111 (l983), pp. 155-170. [Jump back to text.]

14. Plato’s Universe (Seattle, Washington, 1975), p. 19. [Jump back to text.]

15. For a defense of this text and translation see ‘The Significance of kata pant’ a<s>tê in Parmenides Fr. 1.3,’ Ancient Philosophy, Vol. 14 (1994), 1-20. [Jump back to text.]

16. G.E.L. Owen,‘ Eleatic Questions’, Classical Quarterly, Vol. 10 (1960), pp. 84-102. [Jump back to text.]

17. For a discussion of the extent to which Plato assumed a distinctly Greek way of thinking about time and truth, see Jaakko Hintikka, ‘Time, Truth, and Knowledge in Ancient Greek Philosophy’, American Phosophical Quarterly, Vol. 4 (1967), pp. 1-14. There is much in Hintikka’s study that I would not wish to defend (it assumes the correctness of much of the Snell-Fränkel-von Fritz thesis, for example), but Hintikka’s suggestion that both Plato and Aristotle focused their accounts on what can be known about the truth of temporally indefinite sentences seems to me a very useful point to make. [Jump back to text.]

J. H. Lesher
Departments of Classics and Philosophy
University of Maryland
College Park, Maryland 20742

Copyright © 1998, J. H. Lesher

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