The scene is laid in the house of Cephalus at the Piraeus; and the whole dialogue is narrated by Socrates the day after it actually took place to Timaeus Hermocrates, Critias, and a nameless person, who are introduced in the Timaeus.
... Accordingly we went with Polemarchus to his house; and there we found his brothers Lysias and Euthydemus, and with them Thrasymachus the Chalcedonian, Charmantides the Paeanian, and Cleitophon, the son of Aristonymus. There too was Cephalus, the father of Polemarchus, whom I had not seen for a long time, and I thought him very much aged. He was seated on a cushioned chair, and had a garland on his head, for he had been sacrificing in the court; and there were some other chairs in the room arranged in a semicircle, upon which we sat down by him. He saluted me eagerly, and then he said:
You don't come to see me, Socrates, as often as you ought: If I were still able to go and see you I would not ask you to come to me. But at my age I can hardly get to the city, and therefore you should come oftener to the Piraeus. For, let me tell you that the more the pleasures of the body fade away, the greater to me are the pleasure and charm of conversation. Do not, then, deny my request, but make our house your re-sort and keep company with these young men; we are old friends, and you will be quite at home with us.
I replied: There is nothing which for my part I like better, Cephalus, than conversing with aged men; for I regard them as travellers who have gone a journey which I too may have to go, and of whom I ought to inquire whether the way is smooth and easy or rugged and difficult. And this is a question which I should like to ask of you, who have arrived at that time which the poets call the "threshold of old age": Is life harder toward the end, or what report do you give of it?
 I will tell you, Socrates, he said, what my own feeling is. Men of my age flock together; we are birds of a feather, as the old proverb says; and at our meetings the tale of my acquaintance commonly is: I cannot eat, I cannot drink; the pleasures of youth and love are fled away; there was a good time once, but now that is gone, and life is no longer life. The truth is, Socrates, that these regrets, and also the complaints about relations, are to be attributed to the same cause, which is not old age, but men's characters and tempers; for he who is of a calm and happy nature will hardly feel the pressure of age, but to him who is of an opposite disposition youth and age are equally a burden.
...I see that you are indifferent about money, which is a characteristic rather of those who have inherited their fortunes than of those who have acquired them; the makers of fortunes have a second love of money as a creation of their own, resembling the affection of authors for their own poems, or of parents for their children, besides that natural love of it for the sake of use and profit which is common to them and all men. And hence they are very bad company, for they can talk about nothing but the praises of wealth.
That is true, he said.
Yes, that is very true, but may I ask another question?-- What do you consider to be the greatest blessing which you have reaped from your wealth?
One, he said, of which I could not expect easily to convince others. ...  But to him who is conscious of no sin, sweet hope, as Pindar charmingly says, is the kind nurse of his age:
"Hope," he says, "cherishes the soul of him who lives in justice and holiness, and is the nurse of his age and the companion of his journey-- hope which is mightiest to sway the restless soul of man."
How admirable are his words! And the great blessing of riches, I do not say to every man, but to a good man, is, that he has had no occasion to deceive or to defraud others, either intentionally or unintentionally; and when he departs to the world below he is not in any apprehension about offerings due to the gods or debts which he owes to men. Now to this peace of mind the possession of wealth greatly contributes; and therefore I say, that, setting one thing against another, of the many advantages which wealth has to give, to a man of sense this is in my opinion the greatest.
Well said, Cephalus, I replied; but as concerning justice, what is it?--to speak the truth and to pay your debts--no more than this? And even to this are there not exceptions? Suppose that a friend when in his right mind has deposited arms with me and he asks for them when he is not in his right mind, ought I to give them back to him? No one would say that I ought or that I should be right in doing so, any more than they would say that I ought always to speak the truth to one who is in his condition.
You are quite right, he replied.
But then, I said, speaking the truth and paying your debts is not a correct definition of justice.
Quite correct, Socrates, if Simonides is to be believed, said Polemarchus, interposing...
[Cephalus]...he thinks that a friend ought always to do good to a friend, and never evil.
You mean that the return of a deposit of gold which is to the injury of the receiver, if the two parties are friends, is not the repayment of a debt--that is what you would imagine him to say?
And are enemies also to receive what we owe to them?
To be sure, he said, they are to receive what we owe them; and an enemy, as I take it, owes to an enemy that which is due or proper to him--that is to say, evil.
...And so, you and Homer and Simonides are agreed that justice is an art of theft; to be practised, however, "for the good of friends and for the harm of enemies"--that was what you were saying?
No, certainly not that, though I do not now know what I did say; but I still stand by the latter words.
Well, there is another question: By friends and enemies do we mean those who are so really, or only in seeming?
Surely, he said, a man may be expected to love those whom he thinks good, and to hate those whom he thinks evil.
Yes, but do not persons often err about good and evil: many who are not good seem to be so, and conversely?
That is true.
Then to them the good will be enemies and the evil will be their friends?
And in that case they will be right in doing good to the evil and evil to the good?
But the good are just and would not do an injustice?
Then according to your argument it is just to injure those who do no wrong?
Nay, Socrates; the doctrine is immoral.
Then I suppose that we ought to do good to the just and harm to the unjust?
I like that better.
... We should rather say that he is a friend who is, as well as seems, good;  and that he who seems only and is not good, only seems to be and is not a friend; and of an enemy the same may be said.
You would argue that the good are our friends and the bad our enemies?
And instead of saying simply as we did at first, that it is just to do good to our friends and harm to our enemies, we should further say: It is just to do good to our friends when they are good, and harm to our enemies when they are evil?
Yes, that appears to me to be the truth.
But ought the just to injure anyone at all?
... Several times in the course of the discussion Thrasymachus had made an attempt to get the argument into his own hands, and had been put down by the rest of the company, who wanted to hear the end. But when Polemarchus and I had done speaking and there was a pause, he could no longer hold his peace; and, gathering himself up, he came at us like a wild beast, seeking to devour us. We were quite panic-stricken at the sight of him.
He roared out to the whole company: What folly, Socrates, has taken possession of you all? And why, sillybillies, do you knock under to one another? I say that if you want really to know what justice is, you should not only ask but answer, and you should not seek honor to yourself from the refutation of an opponent, but have your own answer; for there is many a one who can ask and cannot answer. And now I will not have you say that justice is duty or advantage or profit or gain or interest, for this sort of nonsense will not do for me; I must have clearness and accuracy.
... Thrasymachus, I said, with a quiver, don't be hard upon us. Polemarchus and I may have been guilty of a little mistake in the argument, but I can assure you that the error was not intentional. If we were seeking for a piece of gold, you would not imagine that we were "knocking under to one another," and so losing our chance of finding it. And why, when we are seeking for justice, a thing more precious than many pieces of gold, do you say that we are weakly yielding to one another and not doing our utmost to get at the truth? Nay, my good friend, we are most willing and anxious to do so, but the fact is that we cannot. And if so, you people who know all things should pity us and not be angry with us. ...
...Will you then kindly answer, for the edification of the company and of myself?
Glaucon and the rest of the company joined in my request, and Thrasymachus, as anyone might see, was in reality eager to speak; for he thought that he had an excellent answer, and would distinguish himself. But at first he affected to insist on my answering; at length he consented to begin. Behold, he said, the wisdom of Socrates; he refuses to teach himself, and goes about learning of others, to whom he never even says, Thank you.
That I learn of others, I replied, is quite true; but that I am ungrateful I wholly deny. Money I have none, and therefore I pay in praise, which is all I have; and how ready I am to praise anyone who appears to me to speak well you will very soon find out when you answer; for I expect that you will answer well.
Listen, then, he said; I proclaim that justice is nothing else than the interest of the stronger. And now why do you not praise me? But of course you won't.
Let me first understand you, I replied. Justice, as you say, is the interest of the stronger. What, Thrasymachus, is the meaning of this? You cannot mean to say that because Polydamas, the pancratiast, is stronger than we are, and finds the eating of beef conducive to his bodily strength, that to eat beef is therefore equally for our good who are weaker than he is, and right and just for us?
That's abominable of you, Socrates; you take the words in the sense which is most damaging to the argument.
Not at all, my good sir, I said; I am trying to understand them; and I wish that you would be a little clearer.
Well, he said, have you never heard that forms of government differ--there are tyrannies, and there are democracies, and there are aristocracies?
Yes, I know.
And the government is the ruling power in each State?
And the different forms of government make laws democratical, aristocratical, tyrannical, with a view to their several interests; and these laws, which are made by them for their own interests, are the justice which they deliver to their subjects, and him who transgresses them they punish as a breaker of the law, and unjust. And that is what I mean when I say that in all States there is the same principle of justice, which is the interest of the government; and as the government must be supposed to have power,  the only reasonable conclusion is that everywhere there is one principle of justice, which is the interest of the stronger.
Now I understand you, I said; and whether you are right or not I will try to discover...
...Do you admit that it is just for subjects to obey their rulers?
But are the rulers of States absolutely infallible, or are they sometimes liable to err?
To be sure, he replied, they are liable to err?
Then in making their laws they may sometimes make them rightly, and sometimes not?
When they make them rightly, they make them agreeably to their interest; when they are mistaken, contrary to their interest; you admit that?
And the laws which they make must be obeyed by their subjects--and that is what you call justice?
Then justice, according to your argument, is not only obedience to the interest of the stronger, but the reverse?
What is that you are saying? he asked.
...Then you must also have acknowledged justice not to be for the interest of the stronger, when the rulers unintentionally command things to be done which are to their own injury. For if, as you say, justice is the obedience which the subject renders to their commands, in that case, O wisest of men, is there any escape from the conclusion that the weaker are commanded to do, not what is for the interest, but what is for the injury of the stronger?
Nothing can be clearer, Socrates, said Polemarchus. 
...Tell me, Thrasymachus, I said, did you mean by justice what the stronger thought to be his interest, whether really so or not?
Certainly not, he said. Do you suppose that I call him who is mistaken the stronger at the time when he is mistaken?
...No artist or sage or ruler errs at the time when he is what his name implies; though he is commonly said to err, and I adopted the common mode of speaking. But to be perfectly accurate, since you are such a lover of accuracy, we should say that the ruler, in so far as he is a ruler, is unerring,  and, being unerring, always commands that which is for his own interest; and the subject is required to execute his commands; and therefore, as I said at first and now repeat, justice is the interest of the stronger.
...does every art require another supplementary art to provide for its interests, and that another and another without end? Or have the arts to look only after their own interests? Or have they no need either of themselves or of another?--having no faults or defects, they have no need to correct them, either by the exercise of their own art or of any other; they have only to consider the interest of their subject-matter. For every art remains pure and faultless while remaining true--that is to say, while perfect and unimpaired. Take the words in your precise sense, and tell me whether I am not right.
Then medicine does not consider the interest of medicine, but the interest of the body?
... Then, I said, no science or art considers or enjoins the interest of the stronger or superior, but only the interest of the subject and weaker?
He made an attempt to contest this proposition also, but finally acquiesced.
Then, I continued, no physician, in so far as he is a physician, considers his own good in what he prescribes, but the good of his patient; for the true physician is also a ruler having the human body as a subject, and is not a mere money-maker; that
has been admitted?
... Then, I said, Thrasymachus, there is no one in any rule who, in so far as he is a ruler, considers or enjoins what is for his own interest, but always what is for the interest of his subject or suitable to his art; to that he looks, and that alone he considers in everything which he says and does.
 When we had got to this point in the argument, ...everyone saw that the definition of justice had been completely upset, Thrasymachus, instead of replying to me,...so entirely astray are you in your ideas about the just and unjust as not even to know that justice and the just are in reality another's good; that is to say, the interest of the ruler and stronger, and the loss of the subject and servant; and injustice the opposite; for the unjust is lord over the truly simple and just: he is the stronger, and his subjects do what is for his interest, and minister to his happiness, which is very far from being their own. Consider further, most foolish Socrates, that the just is always a loser in comparison with the unjust. First of all, in private contracts: wherever the unjust is the partner of the just you will find that, when the partnership is dissolved, the unjust man has always more and the just less. Secondly, in their dealings with the State: when there is an income-tax, the just man will pay more and the unjust less on the same amount of income; and when there is anything to be received the one gains nothing and the other much. Observe also what happens when they take an office; there is the just man neglecting his affairs and perhaps suffering other losses, and getting nothing out of the public, because he is just; moreover he is hated by his friends and acquaintance for refusing to serve them in unlawful ways.  But all this is reversed in the case of the unjust man. I am speaking, as before, of injustice on a large scale in which the advantage of the unjust is most apparent; and my meaning will be most clearly seen if we turn to that highest form of injustice in which the criminal is the happiest of men, and the sufferers or those who refuse to do injustice are the most miserable--that is to say tyranny, which by fraud and force takes away the property of others, not little by little but wholesale; comprehending in one, things sacred as well as profane, private and public; for which acts of wrong, if he were detected perpetrating any one of them singly, he would be punished and incur great disgrace--they who do such wrong in particular cases are called robbers of temples, and man-stealers and burglars and swindlers and thieves. But when a man besides taking away the money of the citizens has made slaves of them, then, instead of these names of reproach, he is termed happy and blessed, not only by the citizens but by all who hear of his having achieved the consummation of injustice. For mankind censure injustice, fearing that they may be the victims of it and not because they shrink from committing it. And thus, as I have shown, Socrates, injustice, when on a sufficient scale, has more strength and freedom and mastery than justice; and, as I said at first, justice is the interest of the stronger, whereas injustice is a man's own profit and interest.
Thrasymachus, when he had thus spoken, having, like a bath-man, deluged our ears with his words, had a mind to go away. But the company would not let him; they insisted that he should remain and defend his position; and I myself added my
own humble request that he would not leave us. Thrasymachus, I said to him, excellent man, how suggestive are your remarks! And are you going to run away before you have fairly taught or learned whether they are true or not?...  ...For my own part I openly declare that I am not convinced, and that I do not believe injustice to be more gainful than justice, even if uncontrolled and allowed to have free play. For, granting that there may be an unjust man who is able to commit injustice either by fraud or force, still this does not convince me of the superior advantage of injustice, and there may be others who are in the same predicament with myself. Perhaps we may be wrong; if so, you in your wisdom should convince us that we are mistaken in preferring justice to injustice.
And how am I to convince you, he said, if you are not already convinced by what I have just said; what more can I do for you? Would you have me put the proof bodily into your souls?
Heaven forbid! I said; I would only ask you to be consistent; or, if you change, change openly and let there be no deception.
...Then now, Thrasymachus, there is no longer any doubt that neither arts nor governments provide for their own interests; but, as we were before saying, they rule and provide for the interests of their subjects who are the weaker and not the
stronger--to their good they attend and not to the good of the superior. And this is the reason, my dear Thrasymachus, why, as I was just now saying, no one is willing to govern; because no one likes to take in hand the reformation of evils which are not his concern, without remuneration. For,  in the execution of his work, and in giving his orders to another, the true artist does not regard his own interest, but always that of his subjects; and therefore in order that rulers may be willing to rule, they must be paid in one of three modes of payment, money, or honor, or a penalty for refusing.
What do you mean, Socrates? said Glaucon. The first two modes of payment are intelligible enough, but what the penalty is I do not understand, or how a penalty can be a payment.
You mean that you do not understand the nature of this payment which to the best men is the great inducement to rule? Of course you know that ambition and avarice are held to be, as indeed they are, a disgrace?
And for this reason, I said, money and honor have no attraction for them; good men do not wish to be openly demanding payment for governing and so to get the name of hirelings, nor by secretly helping themselves out of the public revenues to get the name of thieves. And not being ambitious they do not care about honor. Wherefore necessity must be laid upon them, and they must be induced to serve from the fear of punishment. And this, as I imagine, is the reason why the forwardness to take office, instead of waiting to be compelled, has been deemed dishonorable. Now the worst part of the punishment is that he who refuses to rule is liable to be ruled by one who is worse than himself. And the fear of this, as I conceive, induces the good to take office, not because they would, but because they cannot help--not under the idea that they are going to have any benefit or enjoyment themselves, but as a necessity, and because they are not able to commit the task of ruling to anyone who is better than themselves, or indeed as good. For there is reason to think that if a city were composed entirely of good men, then to avoid office would be as much an object of contention as to obtain office is at present; then we should have plain proof that the true ruler is not meant by nature to regard his own interest, but that of his subjects; and everyone who knew this would choose rather to receive a benefit from another than to have the trouble of conferring one. So far am I from agreeing with Thrasymachus that justice is the interest of the stronger. This latter question need not be further discussed at present; but when Thrasymachus says that the life of the unjust is more advantageous than that of the just, his new statement appears to me to be of a far more serious character. Which of us has spoken truly? And which sort of life, Glaucon, do you prefer?
I for my part deem the life of the just to be the more advantageous, he answered.
 Did you hear all the advantages of the unjust which Thrasymachus was rehearsing?
Yes, I heard him, he replied, but he has not convinced me.
Then shall we try to find some way of convincing him, if we can, that he is saying what is not true?
Most certainly, he replied.
...Well, then, Thrasymachus, I said, suppose you begin at the beginning and answer me. You say that perfect injustice is more gainful than perfect justice?...
And do the unjust appear to you to be wise and good?
Yes, he said; at any rate those of them who are able to be perfectly unjust, and who have the power of subduing States and nations; but perhaps you imagine me to be talking of cutpurses.
Even this profession, if undetected, has advantages, though they are not to be compared with those of which I was just now speaking.
I do not think that I misapprehend your meaning, Thrasymachus, I replied; but still I cannot hear without amazement that you class injustice with wisdom and virtue, and justice with the opposite.
Certainly I do so class them.
Now, I said, you are on more substantial and almost unanswerable ground; for if the injustice which you were maintaining to be profitable had been admitted by you as by others to be vice and deformity, an answer might have been given to you on received principles;  but now I perceive that you will call injustice honorable and strong, and to the unjust you will attribute all the qualities which were attributed by us before to the just, seeing that you do not hesitate to rank injustice with wisdom and virtue.
You have guessed most infallibly, he replied.
Then I certainly ought not to shrink from going through with the argument so long as I have reason to think that you, Thrasymachus, are speaking your real mind; for I do believe that you are now in earnest and are not amusing yourself at our expense.
I may be in earnest or not, but what is that to you?--to refute the argument is your business.
Very true, I said; that is what I have to do: But will you be so good as answer yet one more question? Does the just man try to gain any advantage over the just?
Far otherwise; if he did he would not be the simple amusing creature which he is.
We may put the matter thus, I said--the just does not desire more than his like, but more than his unlike, whereas the unjust desires more than both his like and his unlike?
Nothing, he said, can be better than that statement.
...[the argument is developed]...
Then the just is like the wise and good, and the unjust like the evil and ignorant?
That is the inference.
And each of them is such as his like is?
That was admitted.
Then the just has turned out to be wise and good, and the unjust evil and ignorant.
Thrasymachus made all these admissions, not fluently, as I repeat them, but with extreme reluctance; it was a hot summer's day, and the perspiration poured from him in torrents; and then I saw what I had never seen before, Thrasymachus blushing. As we were now agreed that justice was virtue and wisdom, and injustice vice and ignorance, I proceeded to another point: Well, I said, Thrasymachus, that matter is now settled; but were we not also saying that injustice had strength--do you remember?
Yes, I remember, he said, but do not suppose that I approve of what you are saying or have no answer...
Then I will repeat the question which I asked before, in order that our examination of the relative nature of justice and injustice  may be carried on regularly. A statement was made that injustice is stronger and more powerful than justice, but now justice, having been identified with wisdom and virtue, is easily shown to be stronger than injustice, if injustice is ignorance; this can no longer be questioned by anyone. But I want to view the matter, Thrasymachus, in a different way: You would not deny that a State may be unjust and may be unjustly attempting to enslave other States, or may have already enslaved them, and may be holding many of them in subjection?
True, he replied; and I will add that the best and most perfectly unjust State will be most likely to do so.
...I should like to know also whether injustice, having this tendency to arouse hatred, wherever existing, among slaves or among freemen, will not make them hate one another and set them at variance and render them incapable of common action?
And even if injustice be found in two only, will they not quarrel and fight, and become enemies to one another and to the just?
Yet is not the power which injustice exercises of such a nature that wherever she takes up her abode, whether in a city, in an army,  in a family, or in any other body, that body is, to begin with, rendered incapable of united action by reason of sedition and distraction? and does it not become its own enemy and at variance with all that opposes it, and with the just? Is not this the case?
And is not injustice equally fatal when existing in a single person--in the first place rendering him incapable of action because he is not at unity with himself, and in the second place making him an enemy to himself and the just? Is not that true, Thrasymachus?
Well, then, proceed with your answers, and let me have the remainder of my repast. For we have already shown that the just are clearly wiser and better and abler than the unjust, and that the unjust are incapable of common action; nay, more, that to speak as we did of men who are evil acting at any time vigorously together, is not strictly true, for, if they had been perfectly evil, they would have laid hands upon one another; but it is evident that there must have been some remnant of justice in them, which enabled them to combine; if there had not been they would have injured one another as well as their victims; they were but half-villains in their enterprises; for had they been whole villains, and utterly unjust, they would have been utterly incapable of action. That, as I believe, is the truth of the matter, and not what you said at first. But whether the just have a better and happier life than the unjust is a further question which we also proposed to consider. I think that they have, and for the reasons which I have given; but still I should like to examine further, for no light matter is at stake, nothing less than the rule of human life.
... Well; and has not the soul an end which nothing else can fulfil? for example, to superintend and command and deliberate and the like. Are not these functions proper to the soul, and can they rightly be assigned to any other?
To no other.
... Then an evil soul must necessarily be an evil ruler and superintendent, and the good soul a good ruler?
And we have admitted that justice is the excellence of the soul, and injustice the defect of the soul?
That has been admitted.
Then the just soul and the just man will live well, and the unjust man will live ill?
That is what your argument proves.
 And he who lives well is blessed and happy, and he who lives ill the reverse of happy?
Then the just is happy, and the unjust miserable?
So be it.
But happiness, and not misery, is profitable?
Then, my blessed Thrasymachus, injustice can never be more profitable than justice.
Let this, Socrates, he said, be your entertainment at the Bendidea.
For which I am indebted to you, I said, now that you have grown gentle toward me and have left off scolding. Nevertheless, I have not been well entertained; but that was my own fault and not yours. As an epicure snatches a taste of every dish which is successively brought to table, he not having allowed himself time to enjoy the one before, so have I gone from one subject to another without having discovered what I sought at first, the nature of justice. I left that inquiry and turned away to consider whether justice is virtue and wisdom, or evil and folly; and when there arose a further question about the comparative advantages of justice and injustice, I could not refrain from passing on to that. And the result of the whole discussion has been that I know nothing at all. For I know not what justice is, and therefore I am not likely to know whether it is or is not a virtue, nor can I say whether the just man is happy or unhappy.