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Reason Shows that Reality is Unchanging

Parmenides (middle of the 6th century BCE to middle of the 5th century BCE)

Parmenides thought that the inquirers into nature were confused about what exists. (He does not identify the inquirers into nature specifically, but this is a natural way to understand his argument and his relation to his predecessors.)

As Parmenides understood the inquirers into nature, they thought that the objects salient in ordinary experience exist in terms of changes in the nature of reality. (Anaximenes, for example, according to Parmenides, conceives of the existence of drops of water in terms of the compression of air.) Parmenides rejected this description of reality as incoherent. He argues that "reason," which he understands as a certain form of cognition, shows both that coming into and going out of existence are impossible and that reality is a "whole of a single kind and unchanging and perfect."

"[The path] on which mortals, knowing nothing, wander, two headed; for helplessness in their breast directs their wandering thought; they are carried along deaf and blind alike, amazed, uncritical hordes for whom to be and not to be are supposed to be the same and not the same, and the path of all is backward-turning" (DK 28 B 6).

"In no way may this prevail, that things that are not, are. Bar your thought (νόημα) from this way of inquiry, and do not let habit (ἔθος) born from much experience (πολύπειρον) compel you along this way to direct your sightless eye and sounding ear and tongue, but judge by reason (κρῖναι δὲ λόγῳ) the heavily contested testing spoken by me" (DK 28 B 7).

(Elea was a Greek city in what is now southern Italy. This city is far removed from Miletus, which was located in what is now Turkey. The connection between Parmenides and the Milesians is unknown, but may have run through Xenophanes. Xenophanes came from Colophon, near Miletus, and he may have moved to southern Italy. Parmenides himself, in his surviving work, does not mention any of his predecessors by name. This makes it difficult to know for sure that he had Thales and the Milesian inquirers into nature specifically in mind.)


Nothing Comes into or Goes out of Existence

The argument for Parmenides' conclusion about existence proceeds by (a form of argument that has become known as) reductio ad absurdum:

1. Assume that some object o has come into (gone out of) existence.
2. It follows that "it is not" is true of o before (or after) it came into (or went out of) existence.
3. This, however, is absurd: "it is not" can never be true of anything. Otherwise something could both exist and not exist, which is impossible.
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4. Hence, the inquirers into nature are wrong: nothing comes into (or goes out) of existence.


"What birth will you seek for it? How and whence did it grow? I shall not allow you to say nor to think from not being. For it is not to be said nor thought that it is not (οὐ γὰρ φατὸν οὐδὲ νοητόν ἔστιν ὅπως οὐκ ἔστι). And what need would have driven it later rather than earlier, beginning from nothing, to grow? Thus it must either be completely or not all. Nor will the force of conviction (πίστιος) allow anything besides it to come to be ever from not being. Justice has never loosed her fetters to allow it to come to be or to perish, but holds it fast. And the judgment (κρίσις) about these things lies in this: it is or it is not (ἔστιν ἢ οὐκ ἔστιν). But it has been decided, as is necessary, to leave the one way unthought and nameless (for it is no true way), and that the other is and is genuine. And how could what is be in the future? How could it come to be? For if it came into being, it is not: nor is it if it is ever going to be in the future. Coming to be is extinguished and perishing unheard of" (DK 28 B 8).


The conclusion of Parmenides' argument is paradoxical. It is overwhelmingly natural to believe that almost everything both has come into existence and will go out of existence. In this case, if the conclusion is false, as it appears to be, then either one of the premises is false or the argument itself is invalid. (An argument is invalid if it is possible for the conclusion to be false even if all the premises are true. Validity is a virtue in an argument because in such arguments an opponent who accepts the truth of the premises is committed to the truth of the conclusion of the argument.)

To isolate the problem in the argument, it helps to consider the reasoning in the argument in detail.

The argument is a "reduction to absurdity." The assumption for reductio is that something has come into (or will go out of) existence. The intention is to show that this assumption leads to absurdity. So the first step in argument is the assumption that something has come into existence. Let o be such an object. It follows that o did not exist before it came into existence. From this consequence, according to Parmenides, a contradiction follows because reason shows that "o exists" is a necessary condition for the truth of statements about o.

"Come now, and I will tell, and you, hearing, preserve the story the only routes of inquiry there are for thinking (νοῆσαι); the one, that it is and that it is not possible that it not be (ἔστιν τε καὶ ὡς οὐκ ἔστι μὴ εἶναι), is the way of persuasion (πειθοῦς) (for it attends upon truth), the other, that it is not, and that it is right not to be (οὐκ ἔστιν τε καὶ ὡς χρεών ἐστι μὴ εἶναι), this I point out to you is a way altogether indiscernible: for you could not know (γνοίης) what is not (for it is not to be accomplished) nor could you point it out..." (DK 28 B 2).

For the same thing is for thinking and for being (τὸ γὰρ αὐτὸ νοεῖν ἐστίν τε καὶ εἶναι)" (DK 28 B 3).


Reference and Existence

Is the truth of "o exists" a necessary condition for the truth of statements about o?

Consider objects that once but now no longer exist. Parmenides himself is an example. He has not existed for some time, for about twenty-five hundred years now. So the statement "Parmenides does not exist" is about Parmenides. It is also true and appears in no way contradictory. If this is right, then it is possible to think about and refer to objects that do not now exist.

Just how this is possible is a further question, but part of the answer lies in the realization that using words to refer to objects is not the same as physically pointing to them.


The Mistake that Underlies the Confusion

Since Parmenides' conclusion about existence is so paradoxical, he needs an explanation for why it seems natural to believe that objects come into and go out of existence. Widespread beliefs are not always true, but initially at least (both then and now) it seems very plausible to think that many things do come into and go out of existence.

Parmenides' explanation is in terms of two forms of human cognition. He describes them as "reason" and "experience." ("[D]o not let habit born from much experience (πολύπειρον) compel you along this way to direct your sightless eye and sounding ear and tongue, but judge by reason (κρῖναι δὲ λόγῳ)..." (DK 8 B 7).)

Just what Parmenides had in mind is unclear, but one possibility is that he thought that the Milesian inquirers did not go far enough in their attempt to get beyond the traditional way of thinking about things. The Milesians rely on "reason" in their inquiries into nature. It is through the use of reason that they try to get beyond the traditional stories involving the gods, but, as Parmenides seems to understand them, they also mistakenly rely on "habit born of much experience." It is a belief formed in what Parmenides calls "experience" that things come into and go out of existence. This belief, however, according to Parmenides, is false. He argues that the form of cognition that he calls "reason" shows that nothing comes into or goes out of existence.


Anaximenes' explanation of rain provides an example of the mistake Parmenides attributes to the inquirers into nature.

Experience seems to show that sometimes it rains, i.e., that sometimes water droplets form in the sky and fall to the ground. To explain this phenomenon, Anaximenes uses the new style of explanation that the Milesian inquirers into nature introduced. He says that air is the nature of reality. Air is. It is everlasting. It never comes into or goes out of existence. At the same time, Anaximenes says that a droplet of water is air in a condensed state and that the droplet comes into and goes out existence with changes in the state of air. In this way, about a droplet of water, Parmenides thinks that Anaximenes says something absurd. As he understands him, Anaximenes says of the droplet that it comes into when air becomes condensed. Parmenides, however, is convinced that the reductio argument shows that nothing can come into or go out of existence, and so he concludes that Anaximenes and the Milesian inquirers into nature are confused about what there is.

"It has been named all the names which mortals have laid down, believing them to be true, coming-into-being and perishing, being and not being, changing place and altering bright color" (DK 28 B 8).

Reason and Experience

Parmenides' explanation of the mistake proceeds in terms of an analysis of the enlightenment attitude.

He supposes that in human beings there are various forms of cognition. He supposes that different kinds of cognition are involved in belief formation and retention. He supposes that some of this cognition is properly categorized as "reason," and he supposes that some of this cognition is properly categorized as "experience." He gives an example of "reason," but he does not identify either "reason" or "experience" with a determinate set of cognitive procedures. He seems instead to understand the contrast imprecisely.

It can be tempting to think that we know what these two forms of cognition are, at least in part because the words 'reason' and 'experience' are so familiar to us, but it is important not to assume that the ancient philosophers conceive of reason and experience in the same way we do. It was an ongoing project to understand the states and processes in thinking.

"[The Presocratics] suppose that thought (φρόνησιν) is sense-perception (αἴσθησιν) and that sense-perception is alteration. ... It appears that Homer too to held this view because he made Hector, when he was stunned by the blow, lie with other thoughts (ἀλλοφρονέοντα)—thus implying that even those who are out of their minds still think, although not the same thoughts" (Aristotle, Metaphysics .4.1009b). (The only passage in our text of Homer to which Aristotle's reference could apply is Illiad 23.698, but there the subject is Euryalus, not Hector.)


Two Important Points

1. Parmenides and the Milesian inquirers are both part of the enlightenment tradition.

Part of the import of the new Milesian inquiry into nature is that the ordinary conception of reality, the conception in terms of the gods, is a misleading product of (what Parmenides calls) a "habit born from much experience." The Milesians thought that clear thinking shows that this conception of reality is confused. Really, according to the Milesians, although ordinary experience makes this hard to see, things happen in the world in terms of changes in the nature of reality. (Rain, for example, according to Anaximenes, comes and goes in terms of the condensation of air.)

Parmenides takes this Milesian idea a step further. According to Parmenides, the confusion produced by the reliance on "experience" is much deeper than the Milesians had realized. Parmenides thought that the ordinary conception of reality as objects that come into and go out of existence is itself a product of "experience" that "reason" shows is confused.


2. Parmenides' role in the enlightenment tradition is seminal in the history of philosophy.

Parmenides is an early participant in what became a long-lived effort to understand knowledge. His distinction between "reason" and "experience" is imprecise, and the argument he gives as an example of "reason" may be confused. Nevertheless, the general contrast between "reason" and "experience" becomes an integral part of the subsequent philosophical tradition.

A tradition of empiricism (which Plato and Aristotle mention and which later shows itself in the Epicurean tradition and in Academic and Pyrrhonian Skepticism) exists in ancient philosophy, but rationalism becomes the dominant philosophical position. Plato, Aristotle, and the Stoics hold that "knowledge" (ἐπιστήμη) is essentially a matter of "reason," not "experience."




Perseus Digital Library:
Henry George Liddell, Robert Scott, A Greek-English Lexicon:
αἴσθησις, aisthēsis, noun, "sensation,"
ἀλλοφρονέω, allophroneō, verb, "think of other things,"
εμπειρία, empeiria, noun, "experience,"
ἐπιστήμη, epistēmē, noun, "knowledge,"
δόξα, doxa, noun, "belief,"
κρίσις, krisis, noun, "judgment,"
λόγος, logos, noun, "reason,"
πολύπειρος, polypeiros, adjective, "much-experienced,"
φρόνησις, phronēsis, noun, "sensibleness [= "the ability to behave sensibly"]"

Arizona State University Library.
Loeb Classical Library: Early Greek Philosophy, Volume V: Western Greek Thinkers, Part 2,


"[I]f any of doctors who practice medicine by empirical methods without reason (ἐμπειρίαις ἄνευ λόγου τὴν) were to come upon a free-born doctor conversing with a free-born patient, and using arguments (λόγοις), much as a philosopher (φιλοσοφεῖν) would, dealing with the course of the ailment from its origin and surveying the natural constitution of the human body,—he would at once break out into a roar of laughter, and the language he would use would be none other than that which always comes ready to the tongue of most so-called doctors: 'You fool,' he would say, 'you are not doctoring your patient, but schooling him, so to say, as though what he wanted was to be made, not a sound man, but a doctor'" (Plato, Laws IX.857c-e).