In what sense or senses does Heraclitus believe in
'the unity of opposites'?


According to Diogenes Laertius (circa 3rd century CE)(1), a biographer of the ancient Greek philosophers, in the sixth century BCE, Heraclitus of Ephesus wrote a philosophical work entitled "On Nature".   None of the original work has survived.   Only 139 disjointed fragments remain as quotations in the works of others.   Also according to Diogenes, Heraclitus was a misanthrope who had a very low opinion of the intelligence of his fellow Ephesians.   He made a point of writing in an obscure and complex fashion, making extensive use of poetical metaphors and plays on words, so that none but the already knowledgeable could understand him.   As a consequence, it is very difficult to tease a coherent interpretation out of the little that remains of his text.

A number of the fragments can be interpreted to suggest that Heraclitus thought that opposites are really one.   (See the Appendix for the English translation of those fragments, including referenced in this essay.)   As a result, some interpreters have maintained that Heraclitus'philosophy includes a doctrine of the "unity of opposites"and they have suggested that Heraclitus'philosophy is therefore paradoxical or logically fallacious -- since opposites are clearly contradictory.   Aristotle, for example, considered that Heraclitus was thereby denying the principle of the excluded middle.   In his words

The statement of Heraclitus, that everything is and is not, seems to make everything true, but that of Anaxagoras, that an intermediate exists between two contradictories, makes everything false; for when things are blended, the blend is neither good nor not-good, so that it is not possible to say anything truly.(2)

Considering the available remaining diverse fragments, however, there are at least four different ways in which Heraclitus treats what are generally considered to be opposites.   And none of them need be interpreted in the way suggested by Aristotle.

  1. Perspective: The same thing is often viewed with opposite appreciation or justifies opposite descriptions depending on one's point of view.   From B13, pigs like mud, but men do not.   From B9, horses, dogs, and humans have different notions of pleasure.   Asses prefer straw to gold, while men prefer gold to straw.   From B61, the sea is pure for the fish, but impure for man.   From B60, the way up and the way down is one and the same, the difference depending on one's direction of travel.   From B48, the bow is called life (in a play on words), yet it's function is death.   From B58, the work of the surgeon merits a fee (is good) to the surgeon, but is painful (evil) to the patient.   From B103, the beginning and the end of the circumference of a circle are the same.   There is only one thing, yet there can be opposite descriptions of it.
  2. Contrast: Good (and bad) things are recognizable only if we also recognize their opposites.   Things are often defined, recognizable, noticeable only in terms of their opposites.   From B111, health is pleasant and noticeable only because of sickness, good only because of evil, plenty only because of hunger, and so forth.   Things like health and sickness, good and evil, hunger and plenty exist on a scale delineated by opposite extremes.   The scale is one, but with two opposing limits.
  3. Cyclical: Many pairs of opposites follow each other in cycles, and are hence connected in a larger whole.   From B12, the river is one, yet the water is ever changing.   From B57, day and night are separate components of the daily cycle.   From B88, the soul cycles between the living and the dead, the mind cycles between being awake and asleep, the body cycles between being young and old.   From B126, thing cycle between being warm and cold, wet and dry.   This sort of cyclical change presupposes the non-identity of the terms.   What Heraclitus suggests here is not the identity of opposites but the fact that they replace each other in a series of transformations: they are not identical, yet are transformationally equivalent.   Things change yet remain the same.
  4. Tension: Some opposing things exist in dynamic equilibrium.   From B51, the function of both bow and lyre are dependent on the dynamic tension ("backwards-turning attunement") of opposing forces.   The opposing forces exist within the one thing.

From these four different ways in which Heraclitus describes how opposites relate to each other, he appears to draw the conclusion that opposites are illusory.   Opposites do not really exist as separate things.   Only the unitary underlying object or process exists.   The existence of opposites is entirely dependent on one's point of view.   What appear to be opposites are but different perspectives on the underlying hidden unity.   The fragments thus suggest that Heraclitus does not believe that opposites are one (unity), but rather believes that opposites are present in the same thing, or coinstantiated.   That is, that one and the same thing may be both hot and cold, pure and polluted, etc.

Yet that does not capture the whole picture.   There are opposites which are coinstantiated within a single invariant object.   And there are opposites which are coninstantiated within a single invariant process.   The road which can be both the way up and the way down (B60) and the dynamic tension of bow and lyre (B51) exemplify the coinstantiation of opposites in a single thing.   Whereas the unity of day and night, winter and summer, surfeit and hunger (B67) exemplify the coinstantiation of opposites in a unitary cyclical process.

The traditional interpretation of Heraclitus'philosophy is that of a universe in constant change.   Against his philosophical predecessors'idea of the world as a fixed unity, Heraclitus presents the idea of the world as process.   This traditional interpretation is based on those fragments that can be interpreted as exemplifying the coinstantiation of opposites within cyclical processes.   For Heraclitus, according to the traditional understanding, the great truth is that the unity of the world-order ("logos") depends on difference, opposition, and change.   The universe is in a continuous state of dynamic equilibrium of opposites (like the bow and lyre) in a constant flux between opposites (like day and night).   But the process is an ordered one, governed by fundamental principles.   Thus, universal change is accompanied by an eternal unchanging governing canon -- the "logos".

The fragments that suggest a succession of opposites (day following night, death following life) provide the evidence for the interpretation that change is central to Heraclitus's thought.   To say that every object manifests some pair of contrary properties cyclically is just to say that every object undergoes change.   For Heraclitus, then, every object is subject to change and is always undergoing some kind of change or other.   But it is likely that Heraclitus's notion of the unity of opposites involved more than just the succession of opposed states that occurs in cases of cyclical change.   His other examples of the coinstantiation of opposites within a single object exemplify the kind of opposition in which the opposites are simultaneously present in a single object.  

The example of the bow or lyre suggests the tension between opposed forces.   It seems static, but it is in fact dynamic.   The change that all things experience is driven, according to Heraclitus, by the strife between those opposites that are coinstantiated within any given object (B80, B53).   Beneath an object's apparently motionless exterior is a tension between opposed forces.   This is not obvious to us only because, as Heraclitus also tells us, 'nature loves to hide'(B123) and 'an unapparent connection (harmonia) is stronger than an apparent one'(B54).   When this thought is combined with what Heraclitus says about all things happening by strife and necessity (B80), it can be easily seen how Heraclitus can conclude all things as subject to change.   The illusory appearance of opposites results from that change.   Some opposites appear as a result of a change of perspective.   Others appear from a fixed perspective as the object changes through a cycle or along a scale of defined by opposing limits.

To Heraclitus, therefore, (according to the traditional interpretation of what little remains of his philosophy) all things change.   The change is driven by the strife (war) between opposites (B53, B80).   And the "logos"governs (constrains within rules) that change.   In general, therefore, what we see in Heraclitus is not a conflation of opposites into an identity as is suggested by the phrase "unit of opposites", and the interpretation of Aristotle, but a series of subtle analyses revealing the interconnectedness of contrasting states in life and in the world.   There is no need to impute to him the kind of logical fallacy suggested by Plato and Aristotle, or a fallacious understanding of the phrase "unity of opposites".   Heraclitus would assuredly admit that opposites are a reality, and that correlative opposites are not identical to each other.   But he would equally assuredly maintain that their interconnections are real.


Notes & References

(1)     Diogenes Laertius, The Internet Encyclopedia of Philosophy, URL=<

(2)     Aristotle, Metaphysics, trans. Hippocrates G. Apostle, Bloomington, Ind., 1966.
Book IV, 1012a25-29.

Graham, Daniel W., "Heraclitus", The Stanford Encyclopedia of Philosophy (Spring 2007 Edition), Edward N. Zalta (ed.), URL =                                         <>.

Kirk, G. S., "Natural Change in Heraclitus", Mind, New Series, Vol. 60, No. 237. (Jan., 1951), p 38.

Kirk, G.S., Raven, J.E., Schofield, M., The Presocratic Philosophers, 2nd ed., Cambridge University Press, Cambridge, England, 1957.


B9             For a horse, a dog and a human being have different pleasures; asses prefer straw to gold, since asses find food sweeter than gold.

B10           Graspings: things whole and not whole, what is drawn together and what is drawn asunder, the harmonious and the discordant. The one is made up of all things, and all things issue from the one.

B12           On those who enter the same rivers, ever different waters flow.

B13           Pigs delight in the mire more than in clean water.

B36           For it is death to souls to become water, and death to water to become earth. But water comes from earth; and from water, soul.

B48           The bow (βιός) is called life (βίος), but its work is death.

B51           They do not understand how, though at variance with itself, it agrees with itself. It is a backwards-turning attunement like that of the bow and lyre.

B53           War is father of all and king of all; and some he manifested as gods, some as men; some he made slaves, some free.

B54           An unapparent connection (harmonia) is stronger than an apparent one.

B57           Men are sure that [Hesiod] he knew very many things, he who did not know day and night: they are one.

B58           And good and evil are the same. For doctors, cutting and burning and torturing sick men in every way, still complain that they do not receive as much pay as they deserve from the sick, producing the same things, goods and sicknesses.

B59           The straight and the crooked path of the fuller's comb (γναφεῖον) is one and the same.

B60           The way up and the way down is one and the same.

B61           The sea is the purest and the impurest water. Fish can drink it, and it is good for them; to men it is undrinkable and destructive.

B62           Mortals are immortals and immortals are mortals, the one living the others' death and dying the others' life.

B67           God is day and night, winter and summer, war and peace, surfeit and hunger; but he takes various shapes, just as fire, when it is mingled with spices, is named according to the savor of each.

B80           We must know that war is common to all and strife is justice, and that all things come into being through strife necessarily.

B84a         It rests by changing.

B88           And it is the same thing in us that is quick and dead, awake and asleep, young and old; the former are shifted and become the latter, and the latter in turn are shifted and become the former.

B103         In the circumference of a circle the beginning and the end are common.

B111         It is sickness that makes health pleasant and good; hunger, plenty; weariness, rest.

B123         Nature loves to hide.

B125         Even the posset (barley-drink) separates if it is not stirred.

B126         Cold things become warm, and what is warm cools; what is wet dries, and the parched is moistened

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