Ancient History & Civilisation


Having described the Philosopher Ruler, Plato proceeds to the further education, beyond that described in Part III, necessary to produce him. This further education consists of five mathematical disciplines – arithmetic, plane and solid geometry, astronomy, and harmonics – followed by a training in pure philosophy or ‘Dialectic’ in Plato’s sense. Though some concessions are made to practical utility, the main stress throughout is on the training of the mind, with the vision of the Good as its ultimate objective; and mathematics is to be studied without any immediate practical or scientific aim in view.

As the opening sentences make clear, the education outlined in this Part is to be understood in terms of Sun, Cave, and Line; the point is re-emphasized towards the end of Part VIII, section 3.

1. Preliminary

The type of study required must be one that will provoke the mind to thought.

‘Then would you like us to consider how men of this kind are [521] (c) to be produced, and how they are to be led up to the light, like the men in stories who are said to have risen from the underworld to heaven?’

‘I should like it very much.’

‘It’s not a thing we can settle by spinning for it,’1 I said. ‘What is at issue is the conversion of the mind from a kind of twilight to the true day, that climb up into reality which we shall say is true philosophy.’

‘Yes, of course.’ (d)

So we must try to find out what sort of studies have this effect.’

‘We must.’

‘Well, Glaucon,’ I asked, ‘what should men study if their minds are to be drawn from the world of change to reality? Now it occurs to me that we said our rulers must be trained for war when they were young.’

‘We did.’

‘Then the subject we’re looking for must be relevant in war too.’

‘How do you mean?’

‘It mustn’t be useless to soldiers.’

‘Not if we can avoid it.’

‘Well, we’ve already arranged2 for their physical training and (e) their education in literature and music.’

‘We have.’

‘And of these two, physical training is concerned with the world of change and decay, for the body, which it looks after, grows and declines.’

‘Yes, clearly.’ 522 ‘

So it won’t be the study we are looking for.’


‘Then what about the education in literature and music which we described earlier on?’

‘That,’ he reminded me, ‘was the complement of their physical education. It gave a training by habituation, and used music and rhythm to produce a certain harmony and balance of character and not knowledge; and its literature, whether fictional or factual, had similar effects. There was nothing in it to produce the effect you are seeking.’ (b)

‘Your memory’s quite correct,’ I said, ‘we shan’t find what we want there. But where on earth shall we find it, Glaucon? The more practical forms of skill3 don’t seem very elevating –’

‘Certainly not. But if we exclude them, as well as physical and literary education, what else is there left?’

‘Well, if we can’t think of anything outside them, we must find some feature they all share.’

‘What do you mean?’

‘For example, there is one thing that all occupations, practical, (c) intellectual, or scientific, make use of – one of the first things we must all learn.’


‘Something quite ordinary – to tell the difference between one, two and three; in a word, to count and calculate. Is it not true that every practical or scientific activity must be able to do that?’

‘Yes, it must,’ he agreed.

‘And war as much as any other?’

‘Necessarily so.’

‘I wonder if you have noticed what a silly sort of general (d) Agamemnon is made to look on the stage when Palamedes claims to have invented number, and so organized the army at Troy and counted the ships and everything else. It implies that nothing had been counted before and that Agamemnon, apparently, did not know how many feet he had, if he couldn’t count. What sort of general do you think he made?’

‘A pretty odd one,’ he said, ‘if it’s really true.’

‘So we shall require that a soldier must learn, as well as other (e) things, how to calculate and count.’

‘Yes, of course, if he’s to be able to organize an army, indeed to be human at all.’

‘I wonder, then,’ I asked, ‘if you would agree with me about 523 (a) this branch of study?’

‘In what way?’

‘That it is probably one of the subjects we are looking for, which naturally leads to thought,4 though no one makes proper use of its great power to draw men to reality.’

‘How do you mean?’

‘I’ll try to explain what I have in mind,’ I said, ‘and show you how I distinguish in my own mind between things that have the drawing power I mean and things that have not. If you will follow me and tell me where you agree and disagree, we can then see more clearly whether I have the right idea.’


‘Right,’ I said. ‘You see, there are some perceptions which (b) don’t call for any further exercise of thought, because sensation can judge them adequately, but others which demand the exercise of thought because sensation cannot give a trustworthy result.’

‘You obviously mean things seen at a distance, or drawn in perspective.’

‘No, you haven’t quite got my meaning,’ I replied.

‘Then what do you mean?’ he asked.

‘By perceptions that don’t call for thought I mean those that (c) don’t simultaneously issue in a contrary perception; those that do call for thought are those that do so issue in the sense that in them sensation is ambiguous between two contraries, irrespective of distance. But you will understand more clearly if I put it as follows. Here, we say, are three fingers, the middle, third, and little one.’


‘And you can assume you’ve got what I call a close view of them. But there’s a further point I’d like you to consider.’

‘What is it?’

‘Each of them looks as much a finger as any other, and it (d) makes no difference whether it’s in the middle or at either end, whether it’s white or black, fat or thin, and so on. There is nothing here to force the mind of the ordinary man to ask further questions or to think what a finger is; for at no stage has sight presented the finger to it as being also the opposite of a finger.’

‘No, it hasn’t.’

‘So there’s nothing in this sort of perception likely to call for (e) or stimulate thought.’


‘But what about the size of the fingers? Can sight distinguish properly whether they are large or small? Does it matter which one is in the middle or at the end? And can touch distinguish thickness and thinness or degrees of hardness and softness? Aren’t all the senses in fact deficient in their perception of such qualities? Don’t they operate as follows – touch, for example, which is concerned with hardness, must also be concerned with 524 (a) softness, and reports to the mind that to its perception the same object is both hard and soft.’


‘Then must not the mind find it difficult in such cases to understand what this sense means by hard, if it says the same thing is soft as well? Or again, what light and heavy mean, if the sense concerned indicates that what is heavy is light and what is light is heavy?’

‘Yes; this sort of message puzzles the mind and needs investigation.’(b)

‘It’s probably in this sort of case, then,’ I said, ‘that the mind calls in reasoning5 and thought, and tries to investigate whether one object has been reported to it or two.’


‘And if the answer is two, is not each of the pair a separate entity?’


‘And if each is a separate entity, and between them they make up two, then the mind will perceive two separate entities; for if (c) they weren’t separate it wouldn’t perceive two but one.’

‘That is correct.’

‘But sight, we said, perceives large and small as qualities which are not distinct but run into each other.’

‘Yes, so we said.’

‘And to clear the matter up thought must adopt the opposite approach and look at large and small as distinct and separate qualities – a reverse process to that of sensation.’


‘And from that there follows the question, what then are large and small?’

‘That’s perfectly true.’

‘And that is how we came to use the terms the intelligible and the visible .’6(d)


‘This was what I was trying to say just now, when I said that we are called on to use our reason7 when our senses receive opposite impressions, but that when they do not there is nothing to awaken thought.’

‘Yes, I understand now,’ he said, ‘and agree with you.’

2. The Five Mathematical Studies

Mathematics has, pre-eminently, the characteristics required in section 1, and Plato proceeds to list five mathematical disciplines which the Philosopher Ruler must study.

I. Arithmetic

‘Then in which category do you think the unit and number fall?’

‘I don’t know.’

‘Well, work it out from what we have said,’ I told him. ‘If our perception of the unit, by sight or any other sense, is quite (e) unambiguous, then it does not draw the mind towards reality any more than did our perception of a finger. But if it is always combined with the perception of its opposite, and seems to involve plurality as much as unity, then it calls for the exercise of judgement and forces the mind into a quandary in which it must stir itself to think, and ask what unity in itself is; and if that is so, the study of the unit is among those that lead the mind 525 (a) on and turn it to the vision of reality.’

‘Well, the perception of unity by sight most certainly has this characteristic; for we see the same thing both as a unit and as an unlimited plurality.’

‘And if that’s true of the unit,’ I said, ‘it must be true of number as a whole.’

‘It must.’

‘And number is the concern of counting and calculation.’

‘Of course.’ (b)

‘So both will lead the mind on towards truth.’

‘Yes, they are extraordinarily effective for the purpose.’

‘And so they should be included among the studies we are looking for. Soldiers must study them so that they can organize their armies, and philosophers so that they can, as they must, escape from this transient world to reality; otherwise they will never be able to calculate.’8

‘That is so.’

‘And our Guardians are both soldiers and philosophers.’

‘Of course.’

‘We can, then, properly lay it down that arithmetic shall be a subject for study by those who are to hold positions of responsibility(c) in our state; and we shall ask them not to be amateurish in their approach to it, but to pursue it till they come to understand, by pure thought, the nature of numbers – they aren’t concerned with its usefulness for commercial transactions, as if they were merchants or shopkeepers, but for war and for the easier conversion of the soul from the world of becoming to that of reality and truth.’


‘You know,’ I said, ‘now that we have mentioned the study of arithmetic, it occurs to me what a subtle and widely useful (d) instrument it is for our purpose, if one studies it for the sake of knowledge and not for commercial ends.’

‘How is that?’ he asked.

‘As we have just said, it draws the mind upwards and forces it to argue about numbers in themselves, and will not be put off by attempts to confine the argument to collections of visible or tangible objects. You must know how the experts in the subject, if one tries to argue that the unit itself is divisible, won’t have it, but make you look absurd by multiplying it if you try to divide (e) it, to make sure that their unit is never shown to contain a multiplicity of parts.’

‘Yes, that’s quite true.’

‘What do you think they would say, Glaucon, if one were to 526 (a) say to them, “This is very extraordinary – what are these numbers you are arguing about, whose constituent units are, so you claim, all precisely equal to each other, and at the same time not divisible into parts?”9 What do you think their answer would be to that?’

‘I suppose they would say that the numbers they mean can be apprehended by reason,10 but that there is no other way of handling them.’

‘You see therefore,’ I pointed out to him, ‘that this study looks (b) as if it were really necessary to us, since it so obviously compels the mind to use pure thought in order to get at the truth.’

‘It certainly does have that effect,’ he agreed.

‘Another point – have you noticed how those who are naturally good at calculation are nearly always quick at learning anything else, and how the slow-witted, if trained and practised in calculation, always make progress and improve in speed even if they get no other benefit?’ (c)

‘That is true.’

‘Yet I suppose there’s hardly any form of study which comes harder to those who learn or practise it.’

‘That is true.’

‘For all these reasons, then, we must retain this subject and use it to train our ablest citizens.’

‘I agree.’

II. Plane Geometry

As with arithmetic the emphasis is on intellectual training, not practical usefulness, with the vision of the form of Good as the ultimate objective.

‘That’s one subject settled then. Next let us see if the one that follows it is of any use to us.’

‘Do you mean geometry?’ he asked.


(d) ‘It’s obviously useful in war,’ he said. ‘If a man knows geometry it will make all the difference to him when it comes to pitching camp or taking up a position, or concentrating on deploying an army, or any other military manoeuvre in battle or on the march.’

‘For that sort of purpose,’ I replied, ‘the amount of geometry or calculation needed is small. What we want to find out is whether the subject is on the whole one which, when taken further, has the effect of making it easier to see the form of the (e) good. And that, we say, is the tendency of everything which compels the mind to turn to the region of ultimate blessedness which it must spurn no effort to see.’

‘You are right,’ he said.

‘So it will be useful if, and only if, it compels us to contemplate reality rather than the realm of change.’

‘That’s our view.’

‘Well, then, no one with even an elementary knowledge of 527 (a) geometry will dispute that it’s a science quite the reverse of what is implied by the terms its practitioners use.’


‘The terms are quite absurd, but they are hard put to it to find others. They talk about “squaring” and “applying” and “adding” and so on, as if they were doing something and their reasoning had a practical end, and the subject were not, in fact, pursued for the sake of knowledge.’

‘Yes, that’s very true.’ (b)

‘And we must further agree…’

‘To what?’

‘…that the objects of that knowledge are eternal and not liable to change and decay.’

‘Yes, there’s no question of that: the objects of geometrical knowledge are eternal.’

‘Then it will tend to draw the mind to the truth and direct the philosophers’ reason upwards, instead of downwards, as we wrongly direct it at present.’

‘It is sure to.’

‘Then you must be sure to require the citizens of your ideal (c) state not to neglect geometry. It has considerable incidental advantages too.’

‘What are they?’ he asked.

‘Its usefulness for war, which you have already mentioned,’ I replied; ‘and there is a certain facility for learning all other subjects in which we know that those who have studied geometry lead the field.’

‘They are miles ahead,’ he agreed.

‘So shall we make this the second subject our young men must study?’ ‘


III. Solid Geometry

Though work was being done on solid geometry in Plato’s day, the subject was still, as he makes clear, relatively undeveloped.

(d) ‘And the third should be astronomy. Or don’t you agree?’

‘Yes, I certainly agree. A degree of perception in telling the seasons, months and years is useful not only to the farmer and sailor but equally to the soldier.’

‘You amuse me,’ I said, ‘with your obvious fear that the public will disapprove if the subjects you prescribe don’t seem useful. But it is in fact no easy matter, but very difficult for people to believe that there is a faculty in the mind of each of us which these studies purify and rekindle after it has been ruined and blinded by other pursuits, though it is more worth preserving than any eye since it is the only organ by which we perceive (e) the truth. Those who agree with us about this will give your proposals unqualified approval, but those who are quite unaware of it will probably think you are talking nonsense, as they won’t see what other benefit is to be expected from such studies. Make up your mind which party you are going to reason 528 (a) with – or will you ignore both and pursue the argument largely for your own satisfaction, though without grudging anyone else any profit he may get from it?’

‘That’s what I’ll do,’ he replied; ‘I’ll go on with the discussion chiefly for my own satisfaction.’

‘Then you must go back a bit,’ I said, ‘as we made a wrong choice of subject to put next to geometry.’

‘How was that?’

‘We proceeded straight from plane geometry to solid bodies (b) in motion without considering solid bodies first on their own. The right thing is to proceed from second dimension to third, which brings us, I suppose, to cubes and other three-dimensional figures.’

‘That’s true enough,’ he agreed, ‘but the subject is one which doesn’t seem to have been explored yet, Socrates.’

‘For two reasons,’ I replied. ‘There is no state which sets any value on it, and so, being difficult, it is not pursued with energy; and the pursuit is not likely to be successful without a director, who is difficult to find and, even if found, is unlikely to be obeyed in the present intolerant mood of those who study the subject. But, under the general direction of a state that sets a (c) value on it, their obedience would be assured, and investigations pressed forward continuously and energetically till the problems were cleared up. Even now, with all the neglect and inadequate treatment it has suffered from the public and from students who do not understand its real uses, the subject is so attractive that it makes progress in spite of all handicaps, and it would not be surprising if a solution of its problems were to appear.’

‘Yes, it has very great attractions,’ he said. ‘But explain more (d) clearly what you said just now. You said geometry dealt with plane surfaces.’


‘Then you first said astronomy came next, but subsequently went back on what you had said.’

‘More haste less speed,’ I said. ‘In my hurry I overlooked solid geometry, which should come next, because it’s so absurdly undeveloped, and put astronomy, which is concerned with solids in motion, after plane geometry.’ (e)

‘Yes, that’s what you did,’ he agreed.

‘Then let us put astronomy fourth, and assume that the neglect of solid geometry would be made good under state encouragement.’

IV. Astronomy

In reading Plato’s disparagement of observation here two things should be remembered.

(1) ‘Plato’s primary purpose here is not to advance physical science; but to train the mind to think abstractly’ (Cornford, p. 241). (2) Mathematical astronomy was still only just beginning, and until the astronomer has his mathematical tools he can make no progress; it was the insistence, in the Academy, on the essentially mathematical nature of the problems that led to the rapid progress of astronomy in the two hundred years after Plato’s death. Plato himself later gave a higher place to observation in the Laws andEpinomis; and it should not be forgotten that in the Myth of Er (Part XI, section 3 , 616b ff.) and later in the Timaeus he did try to account in physical terms for the movements of the heavenly bodies.

‘That is fair enough,’ he said. ‘And since you have just been attacking me for commending astronomy for low motives, let 529 (a) me approve of it now on your principles; for it must be obvious to everyone that it, of all subjects, compels the mind to look upwards and leads it from earth to the heavens.’

‘Perhaps I’m an exception,’ I said, ‘for it isn’t obvious to me.’


‘I think that, as it’s at present handled by those who use it as an introduction to philosophy, it makes us look down, not up.’

‘What do you mean?’ he asked.

‘I think you’ve a really high-class idea of the study of “higher things”,’ I replied. ‘Perhaps you think that anyone who puts his (b) head back and gazes at a painted ceiling learns something and is using his mind and not his eyes. You may be right, and I may be just simple minded, but I can’t believe that the mind is made to look upwards except by studying the real and the invisible. If anyone tries to learn anything about the world of sense whether by gaping upwards or blinking downwards,11 I don’t reckon (c) that he really learns – there is no knowledge12 to be had of such things – nor do I reckon his mind is directed upwards, even if he’s lying on his back or floating on the sea.’

‘I’m guilty,’ he said, ‘and deserve to be scolded. But how else do you mean that astronomy ought to be studied if it’s to serve our purpose?’

‘Like this,’ I said. ‘The stars that decorate the sky, though we rightly regard them as the finest and most perfect of visible (d) things, are far inferior, just because they are visible, to the true realities; that is, to the true relative velocities, in pure numbers and perfect figures, of the orbits and what they carry in them,13which are perceptible to reason and thought but not visible to the eye. Do you agree?’


‘Well, then,’ I went on, ‘we ought to treat the visible splendours of the sky as illustrations to our study of the true realities, just as one might treat a wonderful and carefully drawn design by Daedalus or any other artist or draughtsman. Anyone who (e) knew anything about geometry, and saw such a design, would admire the skill with which it was done, but would think it absurd to study it in the serious hope of learning the truth about proportions such as equal or double.’ 530 (a)

‘It would be absurd to hope for that,’ he agreed.

‘Isn’t the true astronomer in the same position when he watches the movements of the stars?’ I asked. ‘He will think that the heavens and heavenly bodies have been put together by their maker as well as such things can be; but he will also think it absurd to suppose that there is an always constant and absolutely invariable relation of day to night, or of day and (b) night to month, or month to year, or, again, of the periods of the other stars to them and to each other. They are all visible and material, and it’s absurd to look for exact truth in them.’

‘I agree now you put it like that,’ he said.

‘We shall therefore treat astronomy, like geometry, as setting us problems for solution,’ I said, ‘and ignore the visible heavens, if we want to make a genuine study of the subject and use it to (c) convert the mind’s natural intelligence to a useful purpose.’

‘You are demanding a lot more work than astronomy at present involves,’ he said.

‘We shall make other demands like it, I think, if we are to be any use as lawgivers. But,’ I asked, ‘can you suggest any other suitable study?’

‘Not at the moment.’

V. Harmonics

Which is to be treated on the same principles as Astronomy.

(d) ‘All the same, there are not one but several species of motion,’ I said. ‘I suppose that an expert could enumerate them all; but even I can distinguish two of them.’

‘What are they?’

‘The one we’ve been talking about and its counterpart.’

‘What’s that?’

‘I think we may say that, just as our eyes are made for astronomy, so our ears are made forthe movements of harmony, and that the two are, as the Pythagoreans14 say, and as we should agree, Glaucon, sister sciences. Isn’t that so?’

‘Yes.’ (e)

‘And as the work involved is considerable we will consult them on the subject, and perhaps on others too. But all through we must maintain the principle we have laid down.’

‘Which principle?’

‘As we said when dealing with astronomy just now, our pupils must not leave their studies incomplete or stop short of the final 531 (a) objective. They can do this just as much in harmonics as they could in astronomy, by wasting their time on measuring audible concords and notes against each other.’

‘Lord, yes, and pretty silly they look,’ he said. ‘They talk about “intervals” of sound, and listen as carefully as if they were trying to hear a conversation next door. And some say they can distinguish a note between two others, which gives them a minimum unit of measurement, while others maintain that there’s no difference between the notes in question. They (b) all prefer to use their ears instead of their minds.’

‘You mean those people who torment the strings and try to wring the truth out of them by twisting them on pegs. I might continue the metaphor15 and talk about strokes of the bow, and accusations against the strings and their shameless denials – but I’ll drop it, because I’m not thinking so much of these people as (c) of the Pythagoreans, who we said would tell us about harmonics. For they do just what the astronomers do; they look for numerical relationships in audible concords, and never get as far as formulating problems and examining which numerical relations are concordant, which not, and why.’

‘But that would be a fear some job,’ he protested.

‘A useful one, none the less,’ I said, ‘when the object is to discover what is valuable and good, though useless if pursued for any other end.’

‘That may well be.’

3. Dialectic

The mathematical studies are only the preliminary to dialectic. We are reminded of the Line and Cave (Partvii, sections 6 and 7). Dialectic is the exercise of pure thought, the highest section of the Line; its object is the vision of the good, the last stage in the ascent from the Cave, when the eye can look at the sun itself. Plato does not profess to give here a full account of dialectic (533a), but we learn some important things about it. It is a process of rational argument (‘dialectic’ means discussion); it is critical of assumptions (such as those of the mathematician), which it ‘destroys’ and relates to a first principle (533c); it tries to grasp what ‘each thing is in itself’ (i.e. its form; 533b); it culminates in coherent knowledge (537c) and in an apprehension of the form of the good(532ab, 534bc).

‘Yes,’ I said, ‘for it’s only if we can pursue all these studies (d) until we see their common ground and relationship, and can work out how they are akin, that they contribute to our purpose and the trouble we spend on them is not lost.’

‘So I should imagine. But it means a great deal of work, Socrates.’

‘And you don’t suppose it’s more than a beginning, do you?’ I asked. ‘The subjects we’ve described are only a prelude to the main theme we have to learn. For you don’t think that people who are good at them are skilled in dialectic, do you?’(e)

‘Heavens, no, though I have come across a few exceptions.’

‘And can they ever acquire any of the knowledge we say they must have if they can’t argue logically?’16

‘No, they can’t.’

532 (a) ‘But isn’t this just the theme which dialectic takes up? It is of course an intellectual theme, but can be represented in terms of vision, as we said, by the progress of sight from shadows to the real creatures themselves, and then to the stars themselves, and finally to the sun itself. So when one tries to get at what each thing is in itself by the exercise of dialectic, relying on reason without any aid from the senses, and refuses to give up until one (b) has grasped by pure thought what the good is in itself, one is at the summit of the intellectual realm,17 as the man who looked at the sun was of the visual realm.’

‘That’s perfectly true.’

‘And isn’t this progress what we call dialectic?’


‘The prisoners in our cave,’ I went on, ‘were released and turned round from the shadows to the images which cast them and to the fire, and then climbed up into the sunlight; there they (c) were still unable to look at animals and plants and at the light of the sun, but could see18 reflections in water and shadows of things (real things, that is, and not mere images throwing shadows in the light of a fire itself derivative compared with the sun). Well, the whole study of the sciences we have described has the effect of leading the best element in the mind up towards the vision of the best among realities, just as the body’s clearest (d) organ was led to the sight of the brightest of all things in the material and visible world.’19

‘I quite agree with all you’ve said myself,’ said Glaucon; ‘I think it’s difficult to accept completely, but in another way hard to deny. However, as this isn’t the only occasion on which we shall hear about it and we may often have to return to it in the future, let us assume your account of it is correct and go on to deal with the main theme itself as thoroughly as we have dealt with the prelude. Tell us what sort of power dialectic has, and (e) what forms of it there are and the paths they follow; for these would seem to lead to our destination, where we shall find rest and reach the end of our journey.’

‘My dear Glaucon,’ I said, ‘you won’t be able to follow me 533 (a) further, not because of any unwillingness on my part, but because what you’d see would no longer be an image of what we are talking about but the truth itself, that is, as I see it; one ought not at this point to claim certainty, though one can claim that there is something of the kind to see, don’t you think?’

‘Yes indeed.’

‘And should we add it is only the power of dialectic that can reveal it, and then only to someone experienced in the studies we have just described? There is no other way, is there?’

‘We can claim that with certainty.’

‘Well, at any rate no one can deny that it is some further (b) procedure (over and above those we have been describing) which sets out systematically to determine what each thing essentially is in itself.20 Of other skilled activities21 some are concerned with human opinions or desires, or with growing or making things, or devoted to looking after them when they are grown or made; as for the rest, geometry and the like, though they have some hold on reality, we can see that they are only (c) dreaming about it; they can never wake and look at it as it is, so long as they leave the assumptions they use undisturbed and cannot account for them. For if one’s starting point is something unknown, and one’s conclusion and intermediate steps are made up of unknowns also, how can the resulting consistency ever by any manner of means become knowledge?’

‘It can’t possibly.’

‘Dialectic, in fact, is the only procedure which proceeds by the destruction of assumptions to the very first principle,22 so as (d) to give itself a firm base. When the eye of the mind gets really bogged down in a morass of ignorance, dialectic gently pulls it out and leads it up, using the studies we have described to help it in the process of conversion. These studies we have often, through force of habit, referred to as branches of knowledge , but we really need another term, to indicate a greater degree of clarity than opinion but a lesser degree than knowledge – we (e) used the term “reason” earlier on. But I don’t think we shall quarrel about a word – the subject of our inquiry is too important for that.’

‘We certainly shan’t.’

‘So we shall be content to use any term provided it conveys the degree of clarity of a particular state of mind.’


‘Then let us be content with the terms23 we used earlier on for 534 (a) the four divisions of our line – calling them, in order, pure knowledge (A), reason, belief, and illusion. The last two we class together as opinion, the first two as knowledge (A + B), opinion being concerned with the world of becoming, knowledge (A + B) with the world of reality. Knowledge (A+B) stands to opinion as the world of reality does to that of becoming, and pure knowledge (A) stands to belief and reason to illusion as knowledge (A + B) stands to opinion. The relation of the realities corresponding to knowledge (A + B) and opinion and the twofold divisions into which they fall we had better omit if we’re not to involve ourselves in an argument even longer than we’ve already had.’ (b) ‘

‘Yes,’ said Glaucon; ‘and I agree about your other points, so far as I can follow you.’

‘So you agree in calling a man a dialectician who can take account of the essential nature of each thing; and in saying that anyone who is unable to give such an account of things either to himself or to other people has to that extent failed to understand them.’

‘I can hardly do otherwise.’

‘Then doesn’t the same apply to the good? If a man can’t (c) define the form of the good and distinguish it clearly in his account from everything else, and then battle his way through all objections, determined to give them refutation based on reality and not opinion,24 and come through with his argument unshaken, you wouldn’t say he knew what the good in itself was, or indeed any other good. Any shadowy notion such a man gets hold of is the product of opinion rather than knowledge, and he’s living in a dream from which he will not awake on this (d) side of the other world, where he will finally sleep for ever.’

‘With all that I agree emphatically.’

‘Well, then, if you ever really had the job of bringing up and educating these imaginary children of yours, you would not, I take it, let them reach positions of high responsibility in society while they’re still like irrational lines.’25


‘So you will lay it down that they must devote themselves especially to this discipline, which will enable them to ask and answer questions with the highest degree of understanding.’

‘With your help I will.’ (e)

‘Then you agree that dialectic is the coping-stone that tops our educational system; it completes the course of studies and there is no other study that can rightly be placed above it.’

‘I agree.’

For a summary of the philosophical passages in the Republic and a comparison with the Phaedrus and Symposium see Appendix I.

4. Selection and Curriculum

Plato first emphasizes the moral and, more particularly, intellectual virtues necessary in those who are to embark on the course outlined. He then specifies the length of time needed for each stage and the age at which it should be started. The first stage, described in Part III, lasts till the age of eighteen. From eighteen to twenty there are two years of physical training and military service. Then, between the ages of twenty and thirty, selected candidates are put through the mathematical disciplines; that stage is followed (after further selection) by five years’ dialectic, any earlier introduction to which is, we are reminded, very dangerous; then follow fifteen years’ practical experience in subordinate offices, after which those who have survived all these tests are fully qualified Philosopher Rulers and divide their time between philosophy (which they prefer) and ruling.

‘All you have to do now, then,’ I went on, ‘is to make an 535 (a) allocation, showing who should study these subjects and how.’

‘Yes, that’s all.’

‘Do you remember the kind of people we picked when you were choosing our Rulers?’26

‘Of course I do.’

‘In most respects we should pick those with the same natural qualities – we should prefer the steadiest and bravest and, so far (b) as possible, the best-looking. But we shall also look not only for moral integrity and toughness, but for natural aptitude for this kind of education.’

‘And how would you distinguish that?’

‘Well, my dear chap,’ I said, ‘they need intellectual eagerness, and must learn easily. For the mind shirks mental hardship more than physical; it touches it more nearly, whereas physical labour it can share with the body.’

‘True.’ (c)

‘They must have good memories, determination and a fondness for hard work. How, otherwise, will they be ready to go through with such an elaborate course of study on top of their physical training?’

‘They won’t, unless they have every natural advantage.’

‘Which explains what is wrong with philosophy today and why it has a bad reputation; as we said before,27 it is taken up by those unworthy of it. Philosophy should be wooed by true men, not bastards.’

‘How do you mean?’ he asked. (d)

‘First of all,’ I said, ‘anyone who takes it up must have no crippling inhibitions about hard work. He mustn’t be only half inclined to work, and half not – for instance, a man who is very fond of hunting and athletics and all kinds of physical exercise, but has no inclination to learn, listen and inquire, and dislikes all intellectual effort of that kind. And there are people just as crippled in the opposite way.’

‘That’s very true.’

‘We shall regard as equally handicapped for the pursuit of (e) truth a mind which, while it detests deliberate lying, and will not abide it in itself and is indignant to find it in others, cheerfully acquiesces in conventional misrepresentations28 and feels no indignation when its own ignorance is shown up, but wallows 536 (a) in it like a pig in a sty.’

‘I entirely agree.’

‘We must be as careful to distinguish genuine and bastard in dealing with all the various kinds of human excellence – discipline, courage, breadth of vision, and the rest. Lack of the knowledge needed for such discrimination on the part of an individual or a community merely leads to the unwitting employment of people who are unsound and bogus in some way whether as friends or rulers.’

‘That is very true.’

‘We must avoid these mistakes,’ I went on. ‘If we pick those (b) who are sound in limb and mind and then put them through our long course of instruction and training, Justice herself can’t blame us and we shall preserve the constitution of our society; if we make any other choice the effect will be precisely the opposite, and we shall plunge philosophy even deeper in ridicule than it is at present.’

‘Which would be a shameful thing to do.’

‘It would,’ I agreed. ‘But I’m not sure I’m not being slightly ridiculous at the moment myself.’


‘I was forgetting that we are amusing ourselves with an (c) imaginary sketch, and was getting too worked up. I had in mind as I spoke the unjust abuse which philosophy suffers, which annoyed me, and my anger at the critics made me speak more seriously than I should.’

‘Oh, come!’ he said, ‘you didn’t sound to me too serious.’

‘Well, that’s how I felt as I was speaking. However, don’t let’s forget that when we were making our earlier choice,29 we chose elderly men; but that won’t do now. We mustn’t let Solon30(d) persuade us that there are a lot of things one can learn as one grows old; one is less able to learn then than to run. The time for all serious effort is when we are young.’


‘Arithmetic and geometry and all the other studies leading to dialectic should be introduced in childhood,31 though we mustn’t exercise any form of compulsion in our teaching.’

‘Why?’ he asked.

‘Because a free man ought not to learn anything under duress. (e) Compulsory physical exercise does no harm to the body, but compulsory learning never sticks in the mind.’


‘Then don’t use compulsion,’ I said to him, ‘but let your 537 (a) children’s lessons take the form of play. You will learn more about their natural abilities that way.’

‘There’s something in what you say.’

‘Do you remember,’ I reminded him, ‘that we said that our children ought to be taken on horseback to watch fighting, and, if it was safe, taken close up and given their taste of blood, like hound puppies?’

‘Yes, I remember.’

‘Well, we must enrol in a select number those who show themselves most at home in all these trials and studies and dangers.’ (b)

‘At what age?’ he asked.

‘As soon as their necessary physical training is over. During that time, whether it be two or three years, they won’t be able to do anything else; physical fatigue and sleep are unfavourable to study. And one of the most important tests is to see how they show up in their physical training.’

‘Of course.’

‘After that time, then, at the age of twenty, some of them will be selected for promotion, and will have to bring together the (c) disconnected subjects they studied in childhood and take a comprehensive view of their relationship with each other and with the nature of reality.’

‘That is the only way to acquire lasting knowledge.’

‘And also the best test of aptitude for dialectic, which is the ability to take the comprehensive view.’

‘I agree.’

‘You will have to keep these requirements in view and make (d) a further choice among your selected candidates when they pass the age of thirty. Those who show the greatest perseverance in their studies, in war, and in their other duties, will be promoted to higher privileges, and their ability to follow truth into the realm of pure reality, without the use of sight or any other sense, tested by the power of dialectic. And here, my friend, you will have to go to work very carefully.’

‘Why particularly?’

‘Haven’t you noticed the appalling harm done by dialectic at (e) present?’

‘What harm?’

‘It fills people with indiscipline.’

‘Oh, yes, I’ve noticed that.’

‘And does it surprise you?’ I asked. ‘Aren’t you sorry for the victims?’

‘Why should I be?’

‘Well, imagine an adopted32 child who has been brought up 538 (a) in a large, rich and powerful family, with many hangers-on; when he grows up he discovers that he is not the child of his so-called parents, but can’t discover who his real parents are. Can you imagine how he will feel towards the hangers-on and his supposed parents, first while he still doesn’t know they aren’t his real parents, and then when he does? Shall I tell you what I should expect?’

‘Yes, do.’

‘Well, I should expect that, so long as he didn’t know they (b) weren’t his real parents, he would respect his mother and father and other supposed relations more than the hangers-on, be more concerned with their needs, and less inclined to do or say anything outrageous to them, or to disobey them in matters of importance.’

‘Very likely.’

‘But when he discovered the truth, I should expect him to give up respecting them seriously and devote himself to the hangers-on; their influence with him would increase, he’d associate with them openly and live by their standards, and, unless his (c) natural instincts were particularly decent, he’d pay no more attention to his previously reputed father and relations.’

‘That’s all very likely. But,’ he asked, ‘what bearing has the illustration on those who take up philosophic discussions?’

‘This. There are certain opinions about what is right and honourable in which we are brought up from childhood, and whose authority we respect like that of our parents.’


‘And there are certain habits of an opposite kind, which have (d) a deceitful attraction because of the pleasures they offer, but which no one of any decency gives in to, because he respects the authority of the beliefs of his fathers.’

‘True again.’

‘Yes,’ I said, ‘but what happens when he is confronted with the question, “What do you mean by ‘honourable’?” When he gives the answer tradition has taught him, he is refuted in argument, and when that has happened many times and on many different grounds, he is driven to think that there’s no difference between honourable and disgraceful, and so on with all the other values, like right and good, that he used to revere. (e) What sort of respect for their authority do you think he’ll feel at the end of it all?’

‘He’s bound to show less respect and obedience.’

‘Then when he’s lost any respect or feeling for his former beliefs but not yet found the truth, where is he likely to turn? 539 (a) Won’t it be to a life which flatters his desires?’

‘Yes, it will.’

‘And so we shall see him become a rebel instead of a conformer.’


‘Yet all this is a natural consequence of starting on philosophic discussions in this way, and, as I’ve just said, there’s every reason for us to excuse it.’

‘Yes, and be sorry about it,’ he agreed.

‘Then if you want to avoid being sorry for your thirty-year-olders, you must be very careful how you introduce them to such discussions.’

‘Very careful.’ (b)

‘And there’s one great precaution you can take, which is to stop their getting a taste of them too young. You must have noticed how young men, after their first taste of argument, are always contradicting people just for the fun of it; they imitate those whom they hear cross-examining each other, and themselves cross-examine other people33 like puppies who love to pull and tear at anyone within reach.’

‘They like nothing better,’ he said.

‘So when they’ve proved a lot of people wrong and been (c) proved wrong often themselves, they soon slip into the belief that nothing they believed before was true; with the result that they discredit themselves and the whole business of philosophy in the eyes of the world.’

‘That’s perfectly true,’ he said.

‘But someone who’s a bit older,’ I went on, ‘will refuse to have anything to do with this sort of idiocy; he won’t copy those who contradict just for the fun of the thing, but will be more likely to follow the lead of someone whose arguments are aimed at finding the truth. He’s a more reasonable person and will get philosophy a better reputation.’(d)


‘In fact all we’ve been saying has been said in the attempt to ensure that only men of steady and disciplined character shall be admitted to philosophic discussions, and not anyone, however unqualified, as happens at present.’

‘I entirely agree.’

‘Then suppose twice as long is spent on an exclusive, continuous and intensive study of philosophy as we proposed should be spent on the corresponding physical training, will that be enough?’

‘Do you mean six years or four?’ (e)

‘It doesn’t matter,’ said I; ‘make it five. After that they must be sent down again into the Cave we spoke of, and compelled to hold any military or other office suitable for the young, so that they may have as much practical experience as their fellows. 540 (a)And here again they must be tested to see if they stand up to temptations of all kinds or give way to them.’

‘And how long do you allow for this stage?’

‘Fifteen years. And when they are fifty, those who have come through all our practical and intellectual tests with distinction must be brought to their final trial, and made to lift their mind’s eye to look at the source of all light, and see the good itself, which they can take as a pattern for ordering their own life as (b) well as that of society and the individual. For the rest of their lives they will spend the bulk of their time in philosophy, but when their turn comes they will, in rotation, turn to the weary business of politics and, for the sake of society, do their duty as Rulers, not for the honour they get by it but as a matter of necessity. And so, when they have brought up successors like themselves to take their place as Guardians, they will depart to the islands of the blest,34 and the state will set up a public (c) memorial to them and sacrifice to them, if the Pythian Oracle approves, as divinities, or at any rate as blessed and godlike.’

‘It’s a fine picture you have drawn of our Rulers, Socrates.’

‘And some of them will be women,’ I reminded him. ‘All I have said about men applies equally to women, if they have the requisite natural capacities.’

‘Of course,’ he agreed, ‘if they are to share equally in everything with the men, as we described.’ (d)

‘Well, then, do you agree that the society and constitution we have sketched is not merely an idle dream, difficult though its realization may be? The indispensable condition is that political power should be in the hands of one or more true philosophers. They would despise all present honours as mean and worthless, (e) and care most for doing right and any rewards it may bring; and they would regard justice as being of paramount importance, and, throughout their reorganization of society, serve and forward it.’

‘How would they proceed?’

‘They would begin by sending away into the country all 541 (a) citizens over the age of ten; having thus removed the children from the influence of their parents’ present way of life, they would bring them up on their own methods and rules, which are those which we have been describing. This is the best and quickest way to establish our society and constitution, and for it to prosper and bring its benefits to any people among which it is established.’

‘Yes, that’s much the best way; and I think, Socrates,’ he added, ‘that you have explained very well how such a society would come into existence, if ever it did.’

‘Then haven’t we said enough about this state of ours and the corresponding type of man? For it’s surely obvious what kind of man we shall want.’

‘Perfectly obvious,’ he agreed. ‘And I agree with you that there’s no more to be said.’

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