The Phaedo shows Socrates on the day of his execution. His primary interlocutors are Pythagoreans, and the dialogue is devoted to showing that the lover of wisdom should not fear death. Socrates argues that death is the separation of the soul from the body and that the body stands in the way of wisdom. In death, the soul has the knowledge of forms the lover of wisdom seeks.

The Death of Socrates
The Death of Socrates, Jacques-Louis David, 1787. Plato is seated at the end of the bed. Socrates reaches for the hemlock.

In this way, in the Phaedo (which the fourth dialogue in the tetralogy of dialogues that portrays Socrates, his love of wisdom, and the last day of his life), Plato returns to and deepens the otherworldly outlook that previously showed itself in the Meno in connection with the Theory of Recollection.

(This otherworldly outlook seems to have its roots in the Orphism and Pythagoreanism. In the Orphic religious movement (which takes its name form the mythical musician and poet Orpheus), there is the idea that the afterlife need not be gloomy and the soul can be purified. This idea, which is contrary to the picture in Homer, is also part of Pythagoreanism. In the Apology, at 41a, Socrates says that he would be willing to die many times over if it meant he would meet Orpheus in the afterlife. In the Phaedo, on the day of his death, Socrates has his final conversation with the Pythagoreans, Simmias and Cebes. (They said to be students of the Philolaus (Phaedo 61d) Philolaus was a Pythagorean from Croton (in what is now the south of Italy) and a contemporary of Socrates. Pythagoras founded his school in Croton in about 530 BCE.) Socrates, in the Phaedo, tries to show Simmias and Cebes that the "lover of wisdom" (φιλόσοφος) should not fear death and in fact that those who pursue the "love of wisdom" (φιλοσοφία) correctly are practicing for their existence when they are dead (Phaedo 61c-d, 63b-c, 63e-64a). (Socrates has said previously, at Phaedo 60e-61a, that he has had a dream in which he was instructed to cultivate the Muses and that he thought the instruction was to do what he had been doing because the love of wisdom is the greatest kind of "music" (μουσικῆς). (Orpheus was said to born of the Muse, Calliope. To be "musical" is to be skilled an art over which the Muses presided. The word is used generally of a person of letters and accomplishments. The opposite is to be ἀμαθής (unlearned, ignorant, stupid, boorish).) In the Crito, at 45b, Simmias and Cebes are said to have brought money to aid Socrates in escaping from jail. In the Meno, at 81a-b, Socrates seems to have either the Orphics or the Pythagoreans in mind when introduces the Theory of Recollection in connection with view he has heard from "certain priests and priestesses" that "the soul of man is immortal, and at one time comes to an end, which is called dying, and at another is born again, but never perishes.")

The love of wisdom is now understood to transform the human psychology so that a human being engages in a certain intellectual activity as much as possible. This intellectual activity imitates the existence the soul enjoys in its natural and disincarnate state, a state in which is somehow completely characterized by knowledge of things Socrates calls "forms" (εἴδη) and that somehow are the reality of things. The lover of wisdom transforms himself so that his existence comes to resemble his natural and disincarnate existence. In this state, the soul is fixed in "contemplation" (θεωρία).

Socrates' Intellectual Autobiography

In the Phaedo, Socrates sets out his intellectual autobiography. He says that he was interested in the inquiry into nature when he was young but later gave up this inquiry for his interest in forms.

"When I was young, Cebes, I was tremendously eager for the kind of wisdom (σοφίας) they call inquiry about nature (περὶ φύσεως ἱστορίαν)" (Phaedo 96a).

This interest in the inquiry into nature is surprising. The early dialogues give no hint that the historical Socrates was ever interested in the inquiry into nature. In fact, it is easy to get the impression that he thought that such knowledge might be impossible and that even if it were possible, it would not be part of the expertise for living a good life. Knowledge of the nature of reality does not seem, at least not initially, to be part of what one needs to know to make one's life good and to find happiness. Socrates interest in the early dialogues is in ethical matters.

Why, then, in the Phaedo does Plato represent Socrates as having been interested in the kind of wisdom known as the inquiry into nature?

It might simply be true that Socrates was interested in the inquiry into nature as a young man, despite the fact that Plato does not highlight this interest in earlier dialogues. Nevertheless, even if it is true that Socrates was in the inquiry into nature in his youth, this earlier interest does not seem to be what Plato uses the autobiography passage in the Phaedo to show. Instead, Plato seems to want to show that Socrates' interest in definitions points the way to the "otherwordly" interpretation of the love of wisdom the character is discussing in the middle dialogues.

(Other than the remark in the Phaedo, there is very to show that Socrates was ever "eager" for the inquiry into nature. Diogenes Laertius says that Archelaus brought natural philosophy (φυσικὴν φιλοσοφίαν) to Athens and that Socrates was his student (Lives of the Philosophers II.16), and it is possible that Archelaus is the author of some of the views Aristophanes associates with Socrates in the Clouds. Plato, however, in the Apology, has Socrates deny that he ever pursued the inquiry into nature. "For many accusers have risen up against me before you, who have been speaking for a long time, many years already, and saying nothing true.... [T]hey got hold of most of you in childhood, and accused me without any truth, saying, 'There is a certain Socrates, a wise man, a ponderer over the things in the air and one who has investigated the things beneath the earth and who makes the weaker argument the stronger'" (Apology 18b; cf. Apology 19b-d, 23c-d, 26d).)

Socrates points the way to a new understanding of the love of wisdom

As Plato seems to understand the inquirers into nature, they try to get straight about the existence of things. Their problem, however, is that they make the mistake to which Socrates calls attention in the early dialogues. He explains that he is looking for the universal in some ethical matter, not the way this universal manifests itself in certain range of circumstances. He tells Euthyphro, for example, not to reply to the "What is piety?" question by citing "one or two out of all the numerous actions that are pious," but to tell him "about the form itself by which all pious things are pious." Socrates seems to make this same the point in the Phaedo. He says that "if anyone says to me that a given thing is beautiful because it has a blooming color, or a shape, or something else like that, I dismiss those other things" (100c-d). Moreover, he seems to make this point against the inquirers into nature. He says that when he pursued this inquiry in his youth he went back and forth with respect to the following kinds of questions. "Do heat and cold, by a sort of fermentation, bring about the organization of animals, as some people say? Is the blood, or air, or fire by which we think? Or is it none of these, and does the brain furnish the sensations of hearing and sight and smell, and do memory and opinion arise from these, and does knowledge come from memory and opinion in a state of rest" (96b)? What Socrates discovered, as Plato seems to portray him, is that what thinking is, for example, is not "blood" or anything like that. These kinds of answers to the "What is it?" question are incorrect, and the mistake is the one to which Socrates called attention. It may be that thinking involves "blood" or "air" in some circumstances, but none of these things are what thinking is.

"If anyone says to me that a given thing is beautiful because it has a blooming color, or a shape, or something else like that, I dismiss those other things, for all those things confuse me, and I hold simply and plainly and perhaps foolishly to this, that nothing else makes it beautiful but the presence or communion (call it which you please) of beauty, however it may have been gained; about the way in which it happens, I make no positive statement as yet, but I do insist that beautiful things are made beautiful by beauty. For I think this is the safest answer I can give to myself or to others, I think I shall never be overthrown, and I believe it is safe for me or anyone else to give this answer, that beautiful things are beautiful through beauty" (Phaedo 100c-e).

The Contemplation of Forms

Now Plato's reasons for the change in perspective in the middle dialogues are a little clearer. He seems to have come to understand Socrates' search for definitions as an interest in the forms of things, where these forms are the reality and existence of the things he has Socrates ask about. In its natural and disincarnate state, the soul is somehow fixed in knowledge of the forms. Human beings are psychological beings, the soul is reason and exists independently of the body, and during its existence outside the body, the soul is engaged in "contemplation" (θεωρία) of forms. When the soul enters the body, it forgets itself and its good and wrongly takes on the concerns of the body. Socrates, as Plato seems to understand him, showed how the "love of wisdom" (φιλοσοφία) corrects this mistake. The lover of wisdom transforms himself so that he spends time in "contemplation" and thereby makes himself resembles the natural and disincarnate state of his soul.

"[P]hilosophy (φιλοσοφία) sees that the most dreadful thing about the imprisonment in the body is the fact that it is caused by the lusts (ἐπιθυμίας) of the flesh, so that the prisoner is the chief assistant in his own imprisonment. ... The soul of the true philosopher (ἀληθῶς φιλοσόφου ψυχὴ) ... stands aloof from pleasures and lusts and griefs and fears (ἡδονῶν τε καὶ ἐπιθυμιῶν καὶ λυπῶν καὶ φόβων), so far as it can, considering that when anyone has violent pleasures or fears or griefs or lusts he suffers from them not merely what one might think--for example, illness or loss of money spent or his lusts--but he suffers the greatest and most extreme evil and does not take it into account. ... The evil is that the soul of every man, when it is greatly pleased or pained by anything, is compelled to believe that the object which caused the emotion (πάσχῃ) is very distinct and very true; but it is not. ... Each pleasure or pain bonds the soul as with a nail to the body and rivets it on and makes it corporeal, so that it fancies the things are true which the body says are true. For because it has the same beliefs and pleasures as the body it is compelled to adopt also the same habits and mode of life (ἐκ γὰρ τοῦ ὁμοδοξεῖν τῷ σώματι καὶ τοῖς αὐτοῖς χαίρειν ἀναγκάζεται οἶμαι ὁμότροπός τε καὶ ὁμότροφος γίγνεσθαι), and can never depart in purity to the other world, but must always go away contaminated with the body; and so it sinks quickly into another body again and grows into it, like seed that is sown. Therefore it has no part in the communion with the divine and pure and absolute. ... This, Cebes, is the reason why the true lovers of knowledge (φιλομαθεῖς) are temperate (κόσμιοί) and brave (ἀνδρεῖοι); not for what the many say. ... For the soul of the philosopher would not reason (λογίσαιτ᾽) as others do, and would not think it right that philosophy should set it free, and that then when set free it should give itself again into bondage to pleasure and pain and engage in futile toil.... No, his soul believes that it must gain peace from these emotions, must follow reason (λογισμῷ) and abide always in it, beholding that which is true and divine and not a matter of opinion (τὸ ἀληθὲς καὶ τὸ θεῖον καὶ τὸ ἀδόξαστον), and making that its only food; and in this way it believes it must live, while life endures, and then at death pass on to that which is akin to itself and of like nature, and be free from human ills" (Phaedo 82e-84b).

The Forms are Paradigms Fixed in Nature

The textual evidence for the Theory of Forms is sparse. In the Phaedo, although Socrates stresses the importance of forms and makes suggestive remarks about them, he does not provide much in the way of detail. There is more detail in the Parmenides, which is traditionally thought to be a late dialogue.

The older and wiser Parmenides asks the young Socrates questions, and Socrates has trouble defending his answers. He suggests and retracts various answers, in the manner of his interlocutors in the early dialogues. Finally, he attempts one last answer to defend his belief in forms. He says that "I think the most likely view is this: that the forms exist as paradigms set in nature, and other things resemble them and are imitations and this partaking of forms is, for the other things, simply being modeled after them (τὰ μὲν εἴδη ταῦτα ὥσπερ παραδείγματα ἑστάναι ἐν τῇ φύσει, τὰ δὲ ἄλλα τούτοις ἐοικέναι καὶ εἶναι ὁμοιώματα, καὶ ἡ μέθεξις αὕτη τοῖς ἄλλοις γίγνεσθαι τῶν εἰδῶν οὐκ ἄλλη τις ἢ εἰκασθῆναι αὐτοῖς)" (Parmenides 132d).

If forms are the "paradigms" specified in answer to the request for a definition, then what Socrates asks about in asking for a definition is immune to change. It is "set in nature," despite the fact that it may manifest itself differently in different situations. The Theory of Forms is thus a thesis in ontology, which may be summarized as follows:

  • the things (piety, courage, justice, and so on) that Socrates asks about exist
  • each of these things exists as a form set in nature
  • this form is a paradigm in which ordinary things participate

Why does Plato think that Theory of Forms is plausible?

It is natural to think that the things Socrates asks about are objective. In the Euthyphro, he asks Euthyphro to tell him what piety is. This seems to presuppose that there is something that piety is and that this makes an answer to the 'What is piety?' question true or false. What, then, is this thing that Plato calls the "form" (εἶδος) of piety?

The form of piety (what piety is) does not seem to be a fact about how human beings happen to use words. If it were, it seems that what piety is would change with changes in the way people use the relevant words. This, however, seems implausible. It is hard to see how a change in the way people use words could cause a change in what piety is. Plato, in fact, seems to have thought that what piety is not a fact about sensible things at all. Aristotle says that Plato rejected this possibility because he thought that whereas the definition sets out what is invariant and does not change from situation to situation, there is nothing unchangeable in this way among the sensible things because the sensible things are always changing and in "flux."

"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..." (Parmenides, DK 28 B 2).

"Now call to mind that this is not what I asked you, to tell me one or two of the many holy (ὁσίων) acts, but to tell the essential aspect (εἶδος), by which all holy acts are holy; for you said that all unholy acts were unholy and all holy ones holy by one aspect. Or don't you remember?
I remember, Socrates. Tell me then what this aspect (ἰδέαν) is, that I may keep my eye fixed upon it and employ it as a model (παραδείγματι) and, if anything you or anyone else does agrees with it, may say that the act is holy, and if not, that it is unholy" (Euthyphro 6d-e).

"[H]e would say, 'Stranger from Elis, is it not by justice that the just are just?' So answer, Hippias, as though he were asking the question.
 I shall answer that it is by justice.
 'Then this--I mean justice--is something?'
 'Then, too, by wisdom the wise are wise and by the good all things are good, are they not?'
 Of course.
 'And justice, wisdom, and so forth are something; for the just, wise, and so forth would not be such by them, if they were not something.'
 To be sure, they are something.
 'Then are not all beautiful things beautiful by the beautiful?'
 Yes, by the beautiful.
 By the beautiful, which is something?'
 Yes, for what alternative is there?
 'Tell me, then, stranger,' he will say, 'what is this, the beautiful'" (Hippias Major 287c-d)?

"The philosophies described above were succeeded by the system of Plato, which in most respects accorded with them, but contained also certain peculiar features distinct from the philosophy of the Italians. In his youth Plato first became acquainted with Cratylus and the Heraclitean doctrines--that the whole sensible world is always in a state of flux (ῥεόντων), and that there is no knowledge (ἐπιστήμης) of it--and in after years he still held these opinions. And when Socrates, disregarding the physical universe (τῆς ὅλης φύσεως) and confining his study to ethical (ἠθικὰ) questions, sought in this sphere for the universal (καθόλου) and was the first to concentrate upon definition, (ὁρισμῶν) Plato followed him and assumed that the problem of definition is concerned not with any sensible thing but with entities of another kind; for the reason that there can be no general definition of sensible things, as they are always changing. These entities he called Ideas (ἰδέας), and held that all sensible things are named after them and in virtue of their relation to them; for the plurality of things which bear the same name as the forms exist by participation in them" (Metaphysics I.6.987a-b).

"The theory of forms (εἰδῶν) occurred to those who enunciated it because they were convinced as to the true nature of reality by the doctrine of Heraclitus, that all sensible things are always in a state of flux (ῥεόντων); so that if there is to be any knowledge (ἐπιστήμη)...,, there must be certain other entities, besides sensible ones, which persist. For there can be no knowledge of that which is in flux. Now Socrates devoted his attention to the virtues of character (ἠθικὰς ἀρετὰς), and was the first to seek a general definition of these. ... and he naturally inquired into the essence of things (τὸ τί ἐστιν); for he was trying to reason logically, and the starting-point of all logical reasoning is the essence. ... But whereas Socrates regarded neither universals (καθόλου) nor definitions as existing in separation (χωριστὰ), they gave them a separate existence, and to these universals and definitions of existing things they gave the name of Ideas (ἰδέας)" (Metaphysics XIII.4.1078b).

Perseus Digital Library:
Plato, Phaedo, Parmenides.
Aristotle, Metaphysics
Henry George Liddell, Robert Scott,
A Greek-English Lexicon:

Arizona State University Library. Loeb Classical Library: Early Greek Philosophy, Volume IV: Western Greek Thinkers, Part 1,