The Sophists’ Detractors and Plato’s Representation of Socrates

Everyone who has read the famous image of the Cave remembers that the prisoners still in chains have not seen the sunlit realm outside. Nor have they seen directly the artefacts whose shadows they gaze at. It is easier to forget what it said about how poorly the prisoners know each other:

‘A strange picture’, he (Glaucon) said, ‘–and strange prisoners!’

‘Ones that resemble us,’ I said, ‘since first of all do you think people in that condition will have seen anything of themselves or of each other (ἀλλήλων) except for their shadows, cast by the fire on to the surface of the cave in front of them?’

‘How could they,’ he asked, ‘if they were prevented from moving their heads even once in their whole lives?’ (Republic 515a4–b1, translated by Rowe)

One part of the ignorance represented in the imagery is inadequate understanding of other people: someone at this lowest of epistemic levels cannot ‘see’ directly another at the same dismal level.^[1]

This paper brings together the passages from Plato where Socrates, instead of exposing ignorance about an object of definitional inquiry, such as a virtue, targets a negative comment expressed by one person about another. The victim of the disparagement is often a sophist. In these passages Socrates himself is not criticising the sophists, or showing the difference between what they do and what he as a philosopher does. He is showing some criticism of sophists to have a poor empirical basis, to be poorly argued, to reflect badly on the critic and so on. But he can do that without crediting the sophists themselves with genuine knowledge or expertise, just as one might point out to prisoners in the cave how little they know about some other prisoners whom they are talking down, while taking the whole lot of them to be in a dire epistemic plight.^[2] It is for this reason that I start with the Cave, to emphasize from the outset that a critic of the sophists’ detractors need not endorse the sophists’ claim to expertise.

I list the passages in the order in which they are considered below.^[3]

Sometimes only two or even one of the parties actually speak in the conversation, and the sophists may not be present in person at all. But, whether or not this is reflected in the number of the speakers, the structure of the critique involves three persons: (1) a sophist, or some sophists, or in the dialogue Laches someone compared to a sophist, (2) someone who disparages the sophists, and (3) Socrates, who criticises the sophists’ detractor. That is why I have included the Laches, despite the absence from it of a real sophist, as there the three-person structure is particularly clear.

One way of using these passages would be to challenge the still common view of Plato as hostile to sophists, or at least to refine our understanding of what he finds objectionable in them. Irwin, for example, has already used some of this evidence, particularly the passage from Republic 6, to argue that, in Plato’s view, some criticism of sophists is simply incorrect. Far from corrupting the young and putting forward radical theories about justice and other virtues, sophists are too deferential to, or reliant on, existing views:

If Plato is right about common-sense moral attitudes, then his objection to the sophists is different from the usual one. In his view, their fault is that while they profess to have something better to offer than mere common sense, their understanding of moral questions goes no deeper than common sense, and they do not see what is defective in common sense. Their fault is not that they are too critical of common sense, but that they are not critical enough.^[4]

As an account of the complaint against sophists in the Republic this seems to me exactly right. But in what follows I will ask not what these passages show about Plato’s own attitude to the sophists, but what the relation is between the passages and his account of Socrates, both as an apologist and in his explorations of Socratic philosophy. How do passages where a sophist’s detractor is corrected contribute to Plato’s defence of Socrates’ memory? And what part does correcting the sophists’ detractors play in Socrates’ philosophical practice as Plato represents it?

Let us now proceed to the passage from Republic 6, where Socrates is discussing rule by philosophers. Neither the sophists nor their detractors are present and participating in the conversation. Socrates asks what happens, in existing societies, to people suitable for philosophy: why are most of these people corrupted? Alcibiades is not named, but Plato’s readers are clearly put in mind of him: Socrates says that good looks, nobility, and wealth can make a young inhabitant of a large city susceptible to wild ambitions (494c4–d3).^[5] In the passage relevant for us Socrates asks who should be held responsible for corrupting young people with philosophical potential.

‘Or do you think, as most people (οἱ πολλοί) do, some youths are corrupted (διαφθειρομένους … νέους) by sophists, and that some individual sophists do any corrupting that is worth mentioning? Don’t you think that the very people who say this are the greatest sophists, give the most complete education and make others – young and old, men and women – as they want them to be?’

‘But when do they do that?’ Adeimantus said.

‘When they sit together in droves in assemblies, law-courts, theatres, military camps or some other public massed meeting and with a mighty noise criticize something said or done and praise other things …’ (492a6–b9, my translation, as are the translations that follow)

Ordinary people think that sophists ‘corrupt the young’.^[6] In fact, they themselves are responsible for corruption on a much larger scale; and so, if those responsible for corrupting education should be called ‘sophists’, collectively these people are a greater sophist than those usually associated with the word, such as Protagoras. They fail to recognize that their own behaviour (in the army, the assembly and so on) has a much greater impact on young Athenians than private teaching does. To influence a young person it is not necessary to tell him that this is right, this is wrong, and it is certainly not necessary to spell it out in formal lessons. A young person can be influenced just as much by evaluative reactions (the soldiers’ expressions of contempt for a cautious general, the jurors’ outrage at a trial, and so on), even when the speakers overlook the presence of the young entirely. Think of a young, impressionable Alcibiades serving with the army and hearing the other men decrying their general. All that the soldiers have in mind is the general’s timidity, as they see it, but, even though they do not think of themselves as educators, what they say may still have a profound and lasting effect on the young soldiers sitting with them.^[7]

In this part of the dialogue Socrates has his eye on the philosopher-rulers of Callipolis and the training that they will undergo. He confirms what he has been assuming throughout his discussion of the city from Book 2: education in virtue and vice is ubiquitous and not just a matter of formal study, and so the social and cultural environment in which future rulers grow up needs to be carefully created and refined. Ordinary people take too narrow a view of education when they pin all the blame for corruption on individual teachers, who offer lessons for money, and overlook their own influence.^[8] Socrates’ criticism is directed against these ordinary people, not the sophists themselves. In saying this I do not attribute to Socrates the view that the sophists provide a good education, let alone the education needed for the rulers of Callipolis; soon afterwards he will say that in their teaching sophists offer nothing other than the opinions of ordinary people (493a–d). But that is not the point he is making in the passage quoted above, 492a–b.

When Socrates mentions the belief that sophists corrupt youths, Plato’s readers cannot fail to recall that the historical Socrates was accused in his trial of doing the same (see e.g. Euthyphro 2c2–3a5, Apology 24b8–c1, Diogenes Laertius 2.40, which presents Favorinus’ report of the plaint kept in the public archive).^[9] That Plato is responding to this judicial charge against Socrates, as well as to a misrepresentation of sophists, is made certain by the allusions to Alcibiades in this part of the Republic. But his response is not to distinguish between sophists and Socrates. Rather, Socrates is protected by exactly the same defence that is made on behalf of the sophists: no individual teacher exercises the kind of influence that ordinary people do when gathered in large numbers. So in the particular case of Alcibiades, who divided his time between Socrates, the army and the assembly, Socrates’ influence cannot have been decisive.

Let us now turn to dialogues where a sophist’s detractor is present and does some of the talking. In his conversation with Gorgias and Polus Socrates sets out genuine arts that engage with the soul and body, either by putting them in a good condition or by addressing defects and problems. For the soul, there is the drafting of laws to foster virtue and the exercise of justice to remedy vices and crimes. Each genuine art is imitated by a pseudo-art: sophistry professes to create the virtues, a task that belongs to legislation, and rhetoric gives itself airs as if it were real justice. Although this is the ‘natural’ division (465c4), sophists and orators are easily confused, and they are not sure in their own minds what relation they have to one another (Gorgias 464b2–466a3). Later in the conversation Socrates points out to Callicles that both sophists and political orators find themselves in the ridiculous position of having made worse the very people they profess to have improved. Socrates starts with the sophists and says how unreasonable it is for them to complain about their pupils after claiming to make them virtuous. Callicles responds to the mention of sophists with contempt, but Socrates then notes that the same point applies to orators.^[10]

Socrates: Tell me, by the god of friendship, don’t you think it unreasonable to claim to have made a person good and complain ‘he was made good by me and remained so subsequently – and is wicked’?

Callicles: Yes.

Socrates: Don’t you hear those who claim to educate people in virtue saying things like that?

Callicles: I do, but what can you say about such worthless people?

Socrates: Well, what can you say about those who claim to administer and supervise a city? They claim to make the city as good as can be, but then accuse it, whenever it suits them, of being utterly wicked. Do you think there is any difference between the two groups? Sophist and orator are the same, my friend, or rather close and similar, as I was saying to Polus. But because of your ignorance you suppose one, rhetoric, to be stupendously fine and despise the other. But in truth sophistry is finer than rhetoric, as finer as legislation is than judicial correction, and physical training than medicine. (Gorgias 519e2–520b3)

Callicles fails to see that his political heroes are, in terms of expertise and false promises, on exactly the same footing as sophists. And Socrates increases the shock of his comment by means of a correlation in value between genuine art and its pseudo-art: the arts that create good states of body or soul, legislation and training, are better than the arts that correct defects as and when they occur.^[11] So, if there is to be a hierarchy of pseudo-arts, rhetoric falls below sophistry, as the latter at least claims to make others virtuous, not merely to address deficiencies.

Our next example comes from near the end of the Meno, where Anytus is asked who teaches virtue. Socrates suggests that it must be the people who claim to teach virtue and charge money for it. Even though Anytus sees who fits the description, he makes Socrates say the word ‘sophist’:

Anytus: And just who do you mean by these, Socrates?

Socrates: You know as well as I do that they are those whom people call ‘sophists’.

Anytus: Heavens, don’t speak of them, Socrates! May no relative or friend of mine, from either this city or abroad, fall prey to such madness as to go to see those men and be ruined, because it’s as plain as daylight that they are the ruin and corruption of those who associate with them. (Meno 91b6–5)

Anytus thinks it obvious that sophists corrupt, but it soon turns out that he has no first-hand experience of them at all.^[12]

Socrates: Has a sophist wronged you, Anytus? If not, why are you so angry with them?

Anytus: No, I assure you I’ve never yet even associated with any of them, and I wouldn’t let anyone else connected with me do so either.

Socrates: Then you’re completely without experience of these men?

Anytus: Yes, and I hope to stay that way.

Socrates: You astonish me – how could you know whether this creature contains any good or bad, if you were completely without experience of it?

Anytus: Easily. Whether or not I am without experience of them, I do at least know who they are.

Socrates: Perhaps you’re a clairvoyant, Anytus. For, given what you yourself say, I’d wonder how else you know about them. (92b5–c7)

The passage too has an apologetic function, and this will be important when we decide whether the target is the sophists or their detractor, Anytus. Anytus was one of the accusers at Socrates’ trial, where, as observed above, one part of the charges against Socrates was precisely that he corrupted the young. In this part of the Meno Plato invites his reader to compare Anytus’ ignorant condemnation of sophists as a ‘corruption’ with his historical charge against Socrates, with the insinuation that Anytus’ charge against Socrates was made with almost as much ignorance of the accused as his criticism of sophists here.^[13] The passage is remarkably neutral about the sophists themselves. Socrates neither endorses nor disputes Anytus’ claim that the sophists corrupt the young, although, as we have seen, he disagrees with it in the Republic.^[14] His challenge is to Anytus: you are not in a position to make such a claim.

It then emerges that none of the candidates favoured by Anytus, as teachers of virtue, stands up to scrutiny. Anytus prefers not to name an individual teacher of virtue – he says that any admirable Athenian will make Meno better than the sophists would (92e) – but Socrates insists on a specific, named example of an admirable Athenian who taught virtue. He lists Athenians whom Anytus can be counted on to accept as virtuous, such as Themistocles and Pericles, and points out that the sons of none of these men excelled in the same field as their fathers. The passage thus points to another failing in Anytus: he accuses sophists of corrupting the young, and (as Plato’s readers know) will later bring a charge against Socrates for doing the same thing, and yet he cannot name an Athenian who did the opposite: teach virtue. His interest in education is in this sense one-sided. A similar point is made against Meletus in the Apology (24c10–25c4). Meletus is asked to say by whom the young are improved and flounders in his attempts to give an answer.

This sequel in the Meno to the discussion of sophists is another way of showing that Anytus is not qualified to call Socrates and the sophists corrupters of the young. On the principle that a genuine expert can recognize both good and bad performances in the relevant field (compare Ion 531d–e), Anytus cannot be a genuine expert in education, as he cannot point to good educators. Of course, it may be that there are no good educators in Athens – but then if Anytus were an expert he would be able to see that for himself and give that as his answer. We could describe Anytus as a reverse Ion: Ion’s credentials as an expert are undermined by his narrow interest in Homer, the best poet, and inability to give performances about inferior poets; Anytus concerns himself only with those he regards as bad educators and loses his eloquence when asked to point to good educators.

The object of criticism is thus not the sophists themselves, whatever Socrates might say against them if he were pressed more insistently for his own view on their education. The passage is criticizing Anytus’ negative comment on the sophists (and, in 399 BC, on Socrates): he lacks the direct knowledge of sophists, and the expertise in education, to make such a comment on them (or on Socrates). As in the part of the Republic considered above, Plato’s defence of Socrates relies on a parallel between him and the sophists. It does not take the form of showing differences between him and them.

I now turn to a passage where Socrates operates both as critic and meta-critic, criticising not only a definition but also the negative comments made by one person against another. In the Laches the attempt to define courage develops into a three-way conversation between Socrates and two generals. Of course, no sophist is present, but when Nicias tries to defend a definition of courage as wisdom, Laches compares his behaviour to that of a sophist (‘more suitable for a sophist than for a man the city expects to lead her’, 197d6–8). The comparison may surprise us: what does this definition of courage, and Nicias’ defence of it, have to do with the sophists? Hostile responses to sophists in the fourth century may lie behind it. When Isocrates, whom we will meet again in our discussion of the Euthydemus, lists ingenious ways of wasting time, his examples are denying the possibility of saying what is false; identifying courage, wisdom and justice with one another; and eristic disputation (Helen 1). (Protagoras is mentioned soon afterwards.) Different groups are said to do the three things, but putting them together in a list suggests that they show similar vices or unseriousness.

In the Laches there is no mistaking the fact that we have an exchange between three people, not two. And Nicias’ definition receives not one response but two, an indignant response from Laches and a more measured response from Socrates. Socrates for his part is not simply evaluating a definition and relating it to the interlocutor’s other beliefs: he also criticises what Laches says against the definition and its proponent. One contrast between the responses by Laches and Socrates turns on different uses of the Greek word ποῖος.

Socrates. Our friend seems to me to mean that courage is a kind of wisdom.

Laches: What?! Wisdom, Socrates? (ποίαν, ὦ Σώκρατες, σοφίαν;)

Soc: Is that your question for Nicias?

Laches: Yes.

Soc: Come on, Nicias, tell him what kind of wisdom courage would be, on your account. (ἴθι δή, αὐτῷ εἰπέ, ὦ Νικία, ποία σοφία ἀνδρεία ἂν εἴη κατὰ τὸν σὸν λόγον.) (194d8–e4)

Nicias has heard from Socrates that people are good in the areas where they have wisdom or expertise (194d). He judges this helpful for their discussion of courage and says that the courageous person is wise. Socrates takes him to mean that courage is a kind of wisdom. This is enough to make Laches, who will soon insist that wisdom and courage are distinct (195a), incredulous. In Greek ποῖος, when combined with a word used by the other speaker, marks incredulity or contempt for what has just been said.^[15] But Socrates carries on as if Laches had asked Nicias to specify the kind of wisdom that he has in mind, thus changing an expression of contempt into a request for Nicias to develop his answer further.

Socrates also responds to Laches more directly as meta-critic: he tells Laches to teach Nicias, and not abuse him (195a7), and to let Nicias say what he means in full before expressing agreement or disagreement (196c1–4). Another contrast between Socrates’ criticism and that of Laches lies in their use of counterexamples. Laches objects with counterexamples before Nicias has completed his explanation of what he is trying to convey: Nicias gets as far as saying that courage is knowing what should cause fear or confidence, but before he can explain himself further, Laches says that doctors know what should cause fear in illnesses (presumably they know the symptoms of a fatal or at least severe illness), and yet doctors are not for that reason courageous (195b2–5). Laches thinks this and other counterexamples are decisive – sufficient to show that Nicias is ‘saying nothing’, as the Greek literally means. Nicias then has to explain that knowing what is to be dreaded, as he understands the expression, does not fall within the doctor’s expertise: for it is not for a doctor to say whether, in a particular person’s case, health or illness is better (195c7–d9). Courageous people, as Nicias conceives of them, know what is truly in one’s own interests, and, whether or not that knowledge is more demanding than medicine, it is certainly different from medicine. We see in hindsight that Laches’ objection was premature. By contrast, when Socrates himself responds to Nicias, he first makes it clear that Nicias is treating courage as a form of knowledge that not every person possesses. Only then does he give an example, and it is offered in a very different spirit – not as proof that Nicias is wrong, but as showing the consequences of his view of courage (196c10–e9). Nicias must either say that no animal is courageous or attribute to some animals – the courageous ones – a kind of knowledge that not all people have. Socrates seems to assume that Nicias will take the first option, and so will deny that even famously fierce animals are courageous. This does not make Nicias wrong, but it shows a cost of his definition. Laches then intervenes again – and once again he thinks that the counterexamples are decisive and put Nicias in an impossible position (197a1–5). Again, we are given two contrasting responses to Nicias’ definition, not one. Making this an exchange between three people, not two, enables Plato to explore different ways of responding to a definition, and, within the fictional conversation, to make Socrates show Laches the justice of allowing a definition’s proponent to explain his meaning in full before he is subjected to challenges and counterexamples.

I turn finally to a dialogue where genuine sophists speak, the Euthydemus. By now it should come as less of a surprise that the dialogue does not merely compare and contrast Socrates with the sophists. There are three critical responses to the sophists by people other than Socrates: (1) Crito, (2) Ctesippus and (3) the anonymous critic, a thinly veiled Isocrates.^[16] These three are put in different relations to the conversation between Socrates and the sophists: Ctesippus speaks in it, and so we are invited to compare his heated response to the sophists with Socrates’ more measured response, just as in the Laches; Crito got only a glimpse of the conversation and hears about it on the following day; and the anonymous critic was present but silent during the conversation and gives his negative view of it afterwards to Crito. Socrates for his part is both a critic of the sophists and, again, meta-critic, scrutinizing and correcting other people’s responses to them. The Euthydemus as a whole thus makes its reader consider not only devious sophistical arguments but also the various responses to which they give rise: impatient, dismissive or attentive.

One of the curious points about the discussion of the sophists, at the end of the dialogue, is the use of the word for ‘philosophy’. Both Crito and the anonymous critic think that the sophists are engaged in φιλοσοφία. Socrates does not challenge that, as we would expect, or distinguish between φιλοσοφία and sophistry. He suggests merely that some people practise it badly, just as there are poor generals and poor athletes (307a3–6).

In its layers of narrative and dialogue the Euthydemus is the most complex of the dialogues considered here. I take each detractor of sophists in turn (Ctesippus, Crito, anonymous critic) and outline very briefly what is said against them. Ctesippus is in the thick of the action. He risks getting too close to the sophists and starting to resemble a sophist himself, as Socrates points out (303e7–8).^[17] Even Socrates reports an urge in himself to imitate the sophists (301b1–2), and yet there remains an obvious contrast, reminiscent of the responses to Nicias in the Laches, between Ctesippus’ attempts to outdo the sophists and Socrates, who shows them a quite different kind of argument in his illustrations of protreptic (278e–282d, 288d–293a).^[18]

Although Crito does not think highly of the sophists, he has an emotional detachment that matches his physical distance from the conversation – close enough to see it, but not close enough to hear it (271a). Crito is limited by his inability to hold onto the distinction between philosophy itself and the people who engage in it; he can make the distinction, but lacks the first-hand experience of philosophy for him to keep it in view. This emerges when the anonymous critic condemns both philosophy itself and those who engage in it (‘the thing itself and the people who spend time on it are good-for-nothing and ridiculous’). Crito replies that, although the anonymous critic is wrong to criticize philosophy itself, it is right to criticize people like Euthydemus and Dionysodorus – and even those willing to talk with them in public (305a6–b3). That last part implies some criticism of Socrates himself. But later Crito reveals that his positive evaluation of philosophy is based not on his own engagement with it but his personal regard for Socrates (306d2–307a2): when he is with Socrates, he regrets not giving his sons philosophical education, but when he turns to people willing to teach it, his enthusiasm for philosophy quickly cools. Socrates’ reply shows that it is not enough to distinguish between philosophy and its practitioners: you need also to engage with philosophy first-hand, not at arm’s length (‘test it well’, 307b8) Crito is too distant from philosophy itself to form his own evaluation of it independently of his opinion of people like Socrates.^[19]

Finally, we have the anonymous critic, present but silent while Socrates, Ctesippus and the sophists talk, and thus with an intermediate degree of involvement. This anonymous critic thinks that the sophists too are involved in ‘philosophy’, and yet he is more discriminating than we might at first think. He does not treat Socrates and the brothers as having exactly the same status: whereas he says that the brothers do not care what they say and seize on every utterance, his criticism of Socrates is for being willing to talk to such people (305a1–b3). This critic keeps his fiercest condemnation for the sophists, not Socrates; in his view, Socrates is somehow degrading himself by talking with them.

What then is wrong with his criticism of the sophists? Notice first that it is not clear how he evaluates philosophy. In his exchange with Crito he calls philosophy ‘worthless’ (305a1). But then Socrates says that the anonymous critic, and people like him, position themselves between philosophy and politics and would not agree that either philosophy or politics is bad (306b2–c5). How can philosophy be both worthless and not bad? If we are to read the two passages charitably to Plato as author, we have to take them as showing a conflict within the anonymous critic.^[20] When showing his intellectual credentials and positioning himself in relation to other intellectuals and authorities, sometimes he has to borrow the authority of both politics and philosophy, and in that context he cannot afford to belittle either of them. But when he tries to make himself pre-eminent, he denounces philosophy – or at least philosophy understood as including what Euthydemus and Dionysodorus do. According to Socrates, people like the anonymous critic think that philosophers are the only impediment to their being acclaimed best of all in wisdom.

They think only one thing stands between them and universal esteem: the people involved in philosophy. So they think that if they change the philosophers’ reputation and make them thought worthless, the contest will be over and, with universal acknowledgement, they will carry off the victory-prize for reputation in wisdom. (306c9–d5)

The anonymous critic’s social self-promotion thus involves incompatible claims about the value of philosophy.

A further problem for the anonymous critic (and here the text is more explicit) is his claim both to be intermediate between philosophy and politics and to be superior to both philosophers and politicians. Socrates objects that someone can be intermediate between two valuable professions or kinds of expertise only by falling short of both of them, in this case by being rather less good than politicians at promoting the good of a city, and rather less good than philosophers in their own goal. So the way in which the anonymous critic relates himself to these rivals implies that he is their inferior (306b2–c5).

What do we learn from bringing these passages together? First, the passages from the Republic and Meno should cause us to revise our conception of Plato’s apologetic strategies and priorities. Previous scholarship has argued that Plato defends Socrates’ memory by distinguishing between Socrates and sophists.^[21] But in these passages, at least, the defence relies on creating a parallel between Socrates and a sophist. A person or group makes against sophists a charge reminiscent of the judicial charges brought against Socrates. The apologetic response is not to distinguish between the defendants, Socrates and the sophists, with a view to establishing Socrates’ innocence while allowing for the sophists’ guilt. It is instead to show the injustice, or poor empirical grounding, of the charge against the sophists, and to suggest implicitly that the same complaint can be made against the corresponding historical charge against Socrates. The fact that Plato’s dialogues sometimes defend Socrates’ memory by responding to a charge against sophists confirms the impression that his apologetic writing was more indirect than the largest comparand available to us, Xenophon’s Apology and Memorabilia.^[22] But it also indicates that drawing a line between Socrates and sophists was sometimes less of a priority for Plato than responding to the judicial charges themselves, and that he did not always see the former, a distinction between Socrates and sophists, as the only or best means of denying Socrates’ guilt. Socrates, let us remember, was executed not for being a sophist, but for impiety and corrupting the young.

Secondly, the passages where the detractor is present and corrected in person illustrate an element of Socrates’ philosophical practice not mentioned in recent overviews: scrutinizing and challenging the ways in which his interlocutors criticize other people.^[23] Philosophy as Socrates practises it, especially in the elenchus, is usually regarded as an examination of how his interlocutors conceive of a non-personal subject, particularly one of the virtues, and a demonstration that they know less about that subject than they suppose. Plato’s own portrait of Socrates in the Apology has helped to keep discussion of those practices at the centre of modern accounts.^[24] But sometimes what Socrates corrects is how his interlocutors speak against one another, or about other people not present in the conversation.

Plato seems to have conceived of this not merely as teaching people philosophy but as teaching them how to act virtuously. When Socrates corrects his own attempts to refute Protagoras in the Theaetetus, Plato makes him say that he does so ‘for the sake of justice’ (164e6–7). Protagoras himself is then imagined to say the following, but the words in fact belong to Socrates:

Don’t commit injustice when putting your questions. It makes no sense at all for someone claiming to care for virtue to persevere in doing nothing but injustice in a discussion. And injustice in this sphere is when some fails to do the following: distinguish between when he is expressing himself in a competitive spirit and when in a dialectical spirit, and in the former play around and trip up others as far as he can, but in dialectic act seriously and correct the interlocutor, showing him only the slips where the mistake is of his own making or comes from those whose company he has kept. (167e1–168a2)

Part of Socratic practice, this passage seems to say, is to treat philosophical conversation as a sphere in which injustice can be committed, and to correct oneself when guilty of it. And part of Socrates’ education of others is to make them take the same view of conversation—even when their adversary is or seems to resemble a sophist.^[25]