philosophy is for everyone
and not just philosophers

philosophers should know lots
of things besides philosophy

Philosophical Connections

Electronic Philosopher

Feature Articles

University of London BA

Philosophy Lovers Gallery

PhiloSophos Home

International Society for Philosophers

Heraclitus on the unity of opposites


To: James S.
From: Geoffrey Klempner
Subject: Heraclitus on the unity of opposites
Date: 9 February 2006 09:37

Dear James,

Thank you for your email of 29 January, with your essay for the University of London program in response to the question, 'In what sense or senses does Heraclitus believe in 'the unity of opposites'.'

First, you asked about my other ancient philosophy units. All the units are from the Pathways program on the First philosophers, covering all the Presocratic philosophers plus the sophists Protagoras and Gorgias. I would have loved to have written a program on Socrates, Plato and Aristotle but never got round to it.

As an incentive for sending me more essays, I am happy to let you have the unit or units for any of the Presocratics you happen to be working on.


It was a pleasure to read this. It is a carefully researched and well thought out piece of work. If you produced something of this quality in the examination, you would easily get a first.

I have looked hard for points which are obscure or objectionable. The only criticism I have of what you actually say concerns a point which is itself debatable. This is your exposition of the fourth or your categories of 'unity of opposites, illustrated by the examples of night and day, life and death, sleeping and waking.

You take it to be an 'unremarkable' observation that night is followed by day which is followed by night and so on. As evidence that it is possible to find this simple observation not at all unremarkable but in fact a baffling paradox, I would cite Parmenides' arguments concerning that which 'is'. In the 20th century, McTaggart produced a 'proof' of the unreality of time which starts from the simple observation that something can be F at one time and not-F at another time and proceeds to demonstrate that the very notion of things being different at different times is 'contradictory'.

Heraclitus was obsessed with time. You could go so far as to say that he was the philosopher who discovered time as a deep metaphysical problem. That is why I think that the observation that night follows day, though unremarkable to us, was extremely remarkable to Heraclitus.

Apart from the fact of change, the other thing that the day and night example brings out is the cyclical nature of many physical processes. This distinguishes night and day or sleeping and waking from the example of life and death; the same thing is not alive, then dead, then alive again. Life only comes from death indirectly through a process of living things feeding off dead things (i.e. there is a lack of symmetry compared with the other two cases). It is the cyclical aspect which is itself spectacular proof of the 'unity' of all things. We can imagine a world where there were no such constant cyclic processes serving as a constant backdrop to all that happens.

But let's look at your interpretation. At dusk, it is not possible to say where day ends and night begins. This is an example of the problem of vagueness, illustrated by the ancient paradox of the heap. There seems to me very little evidence of any interest taken by Heraclitus in the problem of vagueness. I also think it would be wrong to characterize vagueness as a case where judgement can only be subjective and not objective. In cases of vagueness people disagree, just as they disagree about judgements of taste. But the underlying reason for the disagreement is fundamentally different. There is a sense in which in making vague judgements we aim to 'get it right', e.g. to use the term 'heap' in accordance with its correct meaning and not our own personal understanding. ('It may not be a heap for you but it's a heap for me' would be a very odd thing to say.)

As you may have gathered from my unit on Heraclitus, I think that it is important to emphasise the historical point that the early philosophers had a very strange notion of 'the opposites'. We read Heraclitus with a relatively sophisticated understanding of relations and relational properties. The early philosophers really believed that 'the hot' was something different from 'the cold'. As I have argued, Anaximenes was there before Heraclitus with a workable theory. But Heraclitus offered the more radical solution.

Your mention of Nietzsche raises fascinating possibilities. I can see how this relates to your treatment of the night and day example. In Nietzsche's metaphysics, 'reality' is understood in a radically 'perspectival' way. There is no objective view, no 'sub specie aeternitatis'. But how close is this to Heraclitus? Heraclitus talks about subjectivity, but always in the context of contrasting men's 'different understandings' with the philosopher's grasp of the one 'truth'. So I would be very cautious about putting a Nietzschean gloss on the 'unity of opposites'.

All the best,