The Beginning of Infinity: Explanations That Transform the World - David Deutsch (2011)

Chapter 10. A Dream of Socrates

SOCRATES is staying at an inn near the Temple of the Oracle at Delphi. Together with his friend CHAEREPHON, he has today asked the Oracle who the wisest man in the world is,* so that they might go and learn from him. But, to their annoyance, the priestess (who provides the Oracle’s voice on behalf of the god Apollo) merely announced, ‘No one is wiser than Socrates.’ Sleeping now on an uncomfortable bed in a tiny and exorbitantly expensive room, SOCRATES hears a deep, melodious voice intoning his name.

HERMES: Greetings, Socrates.

SOCRATES: [Draws the blanket over his head.] Go away. I’ve already made too many offerings today and you’re not going to wring any more out of me. I am too ‘wise’ for that, hadn’t you heard?

HERMES: I seek no offering.

SOCRATES: Then what do you want? [He turns and sees HERMES, who is naked.] Well, I’m sure that some of my associates camped outside will be glad to –

HERMES: It is not them I seek, but you, O Socrates.

SOCRATES: Then you shall be disappointed, stranger. Now kindly leave me to my hard-earned rest.

HERMES: Very well. [He makes towards the door.]


HERMES: [Turns and raises a quizzical eyebrow.]

SOCRATES: [slowly and deliberately] I am asleep. Dreaming. And you are the god Apollo.

HERMES: What makes you think so?

SOCRATES: These precincts are sacred to you. It is night-time and there is no lamp, yet I see you clearly. This is not possible in real life. So you must be coming to me in a dream.

HERMES: You reason coolly. Are you not afraid?

SOCRATES: Bah! I ask you in return: are you a benevolent or a malevolent god? If benevolent, then what do I have to fear? If malevolent, then I disdain to fear you. We Athenians are a proud people – and protected by our goddess, as you surely know. Twice we defeated the Persian Empire against overwhelming odds,* and now we are defying Sparta. It is our custom to defy anyone who seeks our submission.

HERMES: Even a god?

SOCRATES: A benevolent god would not seek it. On the other hand, it is also our custom to give a hearing to anyone who offers us honest criticism, seeking to persuade us freely to change our minds. For we want to do what is right.

HERMES: Those two customs are two sides of the same valuable coin, Socrates. I give you Athenians great credit for honouring them.

SOCRATES: My city is surely deserving of your favour. But why would an immortal want to converse with such a confused and ignorant person as me? I think I can guess your reason: you have repented of your little joke via the Oracle, haven’t you? Indeed, it was rather cruel of you to send us only a mocking answer, considering the distance we have come and the offerings we have made. So please tell me the truth this time, O fount of wisdom: who is really the wisest man in the world?

HERMES: I reveal no facts.

SOCRATES: [Sighs.] Then I beg you – I have always wanted to know this: what is the nature of virtue?

HERMES: I reveal no moral truths either.

SOCRATES: Yet, as a benevolent god, you must have come here to impart some sort of knowledge. What sort will you deign to grant me?

HERMES: Knowledge about knowledge, Socrates. Epistemology. I have already mentioned some.

SOCRATES: You have? Oh – you said that you honour Athenians for our openness to persuasion. And for our defiance of bullies. But it is well known that those are virtues! Surely telling me what I already know doesn’t count as a ‘revelation’.

HERMES: Most Athenians would indeed call those virtues. But how many really believe it? How many are willing to criticize a god by the standards of reason and justice?

SOCRATES: [Ponders.] All who are just, I suppose. For how can anyone be just if he follows a god of whose moral rightness he is not persuaded? And how is it possible to be persuaded of someone’s moral rightness without first forming a view about which qualities are morally right?

HERMES: Your associates out there on the lawn – are they unjust?


HERMES: And are they aware of the connections you have just described between reason, morality and the reluctance to defer to gods?

SOCRATES: Perhaps not sufficiently aware – yet.

HERMES: So it is not true that every just person knows these things.

SOCRATES: Agreed. Perhaps it is only every wise person.

HERMES: Everyone who is at least as wise as you, then. Who else is in that exalted category?

SOCRATES: Is there some high purpose in your continuing to mock me, wise Apollo, by asking me the same question that we asked you today? It seems to me that your joke is wearing thin.

HERMES: Have you, Socrates, never mocked anyone?

SOCRATES: [with dignity] If, on occasion, I make fun of someone, it is because I hope he will help me to seek a truth that neither he nor I yet knows. I do not mock from on high, as you do. I want only to goad my fellow mortal into helping me look beyond that which is easy to see.

HERMES: But what in the world is easy to see? What things are the easiest to see, Socrates?

SOCRATES: [Shrugs.] Those that are before our eyes.

HERMES: And what is before your eyes at this moment?

SOCRATES: You are.

HERMES: Are you sure?

SOCRATES: Are you going to start asking me how I can be sure of whatever I say? And then, whatever reason I give, are you going to ask how I can be sure of that?

HERMES: No. Do you think I have come here to play hackneyed debating tricks?

SOCRATES: Very well: obviously I can’t be sure of anything. But I don’t want to be. I can think of nothing more boring – no offence meant, wise Apollo – than to attain the state of being perfectly secure in one’s beliefs, which some people seem to yearn for. I see no use for it – other than to provide a semblance of an argument when one doesn’t have a real one. Fortunately that mental state has nothing to do with what I do yearn for, which is to discover the truth of how the world is, and why – and, even more, of how it should be.

HERMES: Congratulations, Socrates, on your epistemological wisdom. The knowledge that you seek – objective knowledge – is hard to come by, but attainable. That mental state that you do not seek – justified belief – is sought by many people, especially priests and philosophers. But, in truth, beliefs cannot be justified, except in relation to other beliefs, and even then only fallibly. So the quest for their justification can lead only to an infinite regress – each step of which would itself be subject to error.

SOCRATES: Again, I know this.

HERMES: Indeed. And, as you have rightly remarked, it doesn’t count as a ‘revelation’ if I tell you what you already know. Yet – notice that that remark is precisely what people who seek justified belief do not agree with.

SOCRATES: What? I’m sorry, but that was too convoluted a comment for my allegedly wise mind to comprehend. Please explain what I am to notice about those people who seek ‘justified belief’.

HERMES: Merely this. Suppose they just happen to be aware of the explanation of something. You and I would say that they know it. But to them, no matter how good an explanation it is, and no matter how true and important and useful it may be, they still do not consider it to be knowledge. It is only if a god then comes along and reassures them that it is true (or if they imagine such a god or other authority) that they count it as knowledge. So, to them it does count as a revelation if the authority tells them what they are already fully aware of.

SOCRATES: I see that. And I see that they are foolish, because, for all they know, the ‘authority’ [gestures at HERMES] may be toying with them. Or trying to teach them some important lesson. Or they may be misunderstanding the authority. Or they may be mistaken in their belief that it is an authority –

HERMES: Yes. So the thing they call ‘knowledge’, namely justified belief, is a chimera. It is unattainable to humans except in the form of self-deception; it is unnecessary for any good purpose; and it is undesired by the wisest among mortals.


HERMES: Xenophanes knew it too; but he is no longer among the mortals –

SOCRATES: Is that what you meant when you told the Oracle that no one is wiser than I?

HERMES: [Ignores the question.] Hence, also, I wasn’t referring to justified belief when I asked whether you are sure that I am before your eyes. I was only questioning how you can claim to be ‘seeing clearly’ what is before your eyes when you also claim to be asleep!

SOCRATES: Oh! Yes, you have caught me in an error – but surely only a trivial one. Indeed, you may not be literally before my eyes. Perhaps you are at home on Olympus, sending me a mere likeness of yourself. But in that case you are controlling that likeness and I am seeing it, and referring to it as ‘you’, so I am seeing ‘you’.

HERMES: But that is not what I asked. I asked what is here before your eyes. In reality.

SOCRATES: All right. Before my eyes, in reality, there is – a small room. Or, if you want a literal reply, what is before my eyes is – eyelids, since I expect that they are shut. Yet I see from your expression that you want even more precision. Very well: before my eyes are the inside surfaces of my eyelids.

HERMES: And can you see those? In other words, is it really ‘easy to see’ what is before your eyes?

SOCRATES: Not at the moment. But that is only because I am dreaming.

HERMES: Is it only because you are dreaming? Are you saying that if you were awake you would now be seeing the inside surfaces of your eyelids?

SOCRATES: [carefully] If I were awake with my eyes still closed, then yes.

HERMES: What colour do you see when you close your eyes?

SOCRATES: In a room as dimly lit as this one – black.

HERMES: Do you think that the inside surfaces of your eyelids are black?

SOCRATES: I suppose not.

HERMES: So would you really be seeing them?

SOCRATES: Not exactly.

HERMES: And if you were to open your eyes, would you be able to see the room?

SOCRATES: Only very vaguely. It is dark.

HERMES: So I ask again: is it true that, if you were awake, you could easily see what was before your eyes?

SOCRATES: All right – not always. But nevertheless, when I am awake, and with my eyes open, and in bright light –

HERMES: But not too bright, I suppose?

SOCRATES: Yes, yes. If you want to keep quibbling, I must accept that when one is dazzled by the sun one may see even less well than in the dark. Likewise one may see one’s own face behind a mirror where there is in reality only empty space. One may sometimes see a mirage, or be fooled by a pile of crumpled clothes that happens to resemble a mythical creature –

HERMES: Or one may be fooled by dreaming of one . . .

SOCRATES: [Smiles.] Quite so. And, conversely, whether sleeping or waking, we often fail to see things that are there in reality.

HERMES: You have no idea how many such things there are . . .

SOCRATES: No doubt. But still, when one is not dreaming, and conditions are good for seeing –

HERMES: And how can you tell whether ‘conditions are good’ for seeing?

SOCRATES: Ah! Now you are trying to catch me in a circularity. You want me to say that one can tell that conditions are good for seeing when one can easily see what is there.

HERMES: I want you not to say so.

SOCRATES: It seems to me that you have been asking questions about me – what is in front of me, what I can easily see, whether I am sure, and so on. But I seek fundamental truths, of which I estimate that not a single one is predominantly about me. So let me stress again: I am not sure what is in front of my eyes – ever – with my eyes open or closed, asleep or awake. Nor can I be sure what is probably in front of my eyes, for how could I estimate the probability that I am dreaming when I think I am awake? Or that my whole previous life has been but a dream in which it has pleased one of you immortals to imprison me?

HERMES: Indeed.

SOCRATES: I might even be a victim of a mundane deception, such as those of conjurers. We know that a conjurer is deceiving us because he shows us something that cannot be – and then asks for money! But if he were to forgo his fee and show me something that can be but is not, how could I ever know? Perhaps this entire vision of you is not a dream after all but some cunning conjurer’s trick. On the other hand, perhaps you really are here in person and I am awake after all. None of this can I ever be sure is so, or not so. I can, however, conceive of knowing some of it.

HERMES: Precisely. And is the same true of your moral knowledge? In regard to what is right and wrong, could you be mistaken, or misled, by the equivalent of mirages or tricks?

SOCRATES: That seems harder to imagine. For in regard to moral knowledge I need my senses very little: it is mainly just my own thoughts. I reason about what is right and wrong, or what makes a person virtuous or wicked. I can be mistaken, of course, in these mental deliberations, but not so easily deceived by outside tricks or illusions, for they affect only our senses and not our reason.

HERMES: How, then, do you account for the fact that you Athenians are constantly squabbling among yourselves about what qualities constitute virtue or vice, and what actions are right or wrong?

SOCRATES: Why is that puzzling? We disagree because it is easy to be mistaken. Yet, despite that, we also agree about many such issues.

From this I speculate that, where we have so far failed to agree, it is not because anything is actively deceiving us, but simply because some issues are hard to reason about – just as there are many truths in geometry that even Pythagoras did not know but which future geometers may discover. As that other ‘wise mortal’ Xenophanes wrote:

The gods did not reveal, from the beginning,

All things to us; but in the course of time,

Through seeking we may learn and know things better.*

That is what we Athenians have done in regard to moral knowledge. Through seeking we have learned, and agreed upon, the easy things. And in future, by the same means – namely by refusing to hold any of our ideas immune from criticism – we may learn some matters not so light.

HERMES: There is much truth in what you say. So, take it a little further: if it is so hard to be systematically deceived on moral issues, how is it that the Spartans disagree with you about some of those issues on which nearly all Athenians agree – the ones that you have just said are the easy ones?

SOCRATES: Because the Spartans learn many mistaken beliefs and values in early childhood.

HERMES: Whereas Athenians begin their flawless education at what age?

SOCRATES: Again, you catch me in an error. Yes of course we too teach our values to our young, and those must include our most serious misconceptions as well as our deepest wisdom. Yet our values include being open to suggestions, tolerant of dissent, and critical of both dissent and received opinion. So I suppose that the real difference between the Spartans and us is that their moral education enjoins them to hold their most important ideas immune from criticism. Not to be open to suggestions. Not to criticize certain ideas such as their traditions or their conceptions of the gods; not to seek the truth, because they claim that they already have it.

Hence they do not believe that ‘in the course of time they may learn and know things better.’ They agree among themselves because their laws and customs enforce conformity. We agree among ourselves (to the extent that we do) because, through our tradition of endless critical debate, we have discovered some genuine knowledge. Since there is only one truth of any given matter, as we discover ideas closer to the truth our ideas become closer to each other’s, so we agree more. People who converge upon the truth converge with each other.

HERMES: Indeed.

SOCRATES: Moreover, since the Spartans never seek improvement, it is not surprising that they never find it. We, in contrast, have sought it – by constantly criticizing and debating and trying to correct our ideas and behaviour. And thereby we are well placed to learn more in the future.

HERMES: It follows, then, that it is wrong of the Spartans to educate their children to hold their city’s ideas, laws and customs immune from criticism.

SOCRATES: I thought you weren’t going to reveal moral truths!

HERMES: I can’t help it if it follows logically from epistemology. But, anyway, you already know this one.

SOCRATES: Yes, I do. And I see what you are getting at. You are showing me that there are such things as mirages and tricks in regard to moral knowledge. Some of them are embedded in the Spartans’ traditional moral choices. Their whole way of life misleads and traps them – because one of their mistaken beliefs is that they must take no steps to prevent their way of life from misleading and trapping them!


SOCRATES: Are there such traps embedded in our way of life? [Frowns.] Of course, I think there aren’t – but I would think that, wouldn’t I? As Xenophanes also wrote, it’s all too easy to attribute universal truth to mere local appearances:

The Ethiops say that their gods are flat-nosed and black

While the Thracians say that theirs have blue eyes and red hair.

Yet if cattle or horses or lions had hands and could draw

And could sculpture like men, then the horses would draw their gods

Like horses, and cattle like cattle . . .

HERMES: So now you are imagining some Spartan Socrates who considers their ways virtuous and yours decadent –

SOCRATES: And who considers us to be stuck in a trap, since we shall never willingly ‘correct’ ourselves by adopting Spartan ways. Yes.

HERMES: But does this Spartan Socrates, if he exists, worry that the Athenian Socrates may be right, and he wrong? Was there a Spartan Xenophanes who suspected that the gods might not be as the Greeks think they are?

SOCRATES: Most certainly not!

HERMES: So, since one of their ‘ways’ is to preserve all their ways unchanged, then if he were right, and you wrong –

SOCRATES: Then the Spartans must also have been right ever since they embarked on their present way of life. The gods must have revealed the perfect way of life to them at the outset. So – did you?

HERMES: [Raises his eyebrows.]

SOCRATES: Of course you didn’t. Now I see that the difference between our ways and theirs is not merely a matter of perspective, nor just a matter of degree.* Let me restate it:

If the Spartan Socrates is right that Athens is trapped in falsehoods but Sparta is not, then Sparta, being unchanging, must already be perfect, and hence right about everything else too. Yet in fact they know almost nothing. One thing that they clearly don’t know is how to persuade other cities that Sparta is perfect, even cities that have a policy of listening to arguments and criticism . . .

HERMES: Well, logically it could be that the ‘perfect way of life’ involves having few accomplishments and being wrong about most things. But, yes, you are glimpsing something important here –

SOCRATES: Whereas if I am right that Athens is not in such a trap, that implies nothing about whether we are right or wrong about any other matter. Indeed, our very idea that improvement is possible implies that there must be errors and inadequacies in our current ideas.

I thank you, generous Apollo, for this ‘glimpse’ into that important difference.

HERMES: Yet there is even more of a difference than you think. Bear in mind that the Spartans and Athenians alike are but fallible men and are subject to misconceptions and errors in all their thinking –

SOCRATES: Wait! We are fallible in all our thinking? Is there literally no idea that we may safely hold immune from criticism?

HERMES: Like what?

SOCRATES: [Ponders for a while. Then:] What about the truths of arithmetic, like two plus two equals four? Or the fact that Delphi exists? What about the geometrical fact that the angles of a triangle sum to two right angles?

HERMES: Revealing no facts, I cannot confirm that all three of those propositions are even true! But more important is this: how did you come to choose those particular propositions as candidates for immunity from criticism? Why Delphi and not Athens? Why two plus two and not three plus four? Why not the theorem of Pythagoras? Was it because you decided that the propositions you chose would best make your point because they were the most obviously, unambiguously true of all the propositions you considered using?


HERMES: But then how did you determine how obviously and unambiguously true each of those candidate propositions was, compared with the others? Did you not criticize them? Did you not quickly attempt to think of ways or reasons that they might conceivably be false?

SOCRATES: Yes, I did. I see. Had I held them immune from criticism, I would have had no way of arriving at that conclusion.

HERMES: So you are, after all, a thoroughgoing fallibilist – though you mistakenly believed you were not.

SOCRATES: I merely doubted it.

HERMES: You doubted and criticized fallibilism itself, as a true fallibilist should.

SOCRATES: That is so. Moreover, had I not criticized it, I could not have come to understand why it is true. My doubt improved my knowledge of an important truth – as knowledge held immune from criticism never can be improved!

HERMES: This too you already knew. For it is why you always encourage everyone to criticize even that which seems most obvious to you –

SOCRATES: And why I set an example by doing it to them!

HERMES: Perhaps. Now consider: what would happen if the fallible Athenian voters made a mistake and enacted a law that was very unwise and unjust –

SOCRATES: Which, alas, they often do –

HERMES: Imagine a specific case, for the sake of argument. Suppose that they were somehow firmly persuaded that thieving is a high virtue from which many practical benefits flow, and that they abolished all laws forbidding it. What would happen?

SOCRATES: Everyone would start thieving. Very soon those who were best at thieving (and at living among thieves) would become the wealthiest citizens. But most people would no longer be secure in their property (even most thieves), and all the farmers and artisans and traders would soon find it impossible to continue to produce anything worth stealing. So disaster and starvation would follow, while the promised benefits would not, and they would all realize that they had been mistaken.

HERMES: Would they? Let me remind you again of the fallibility of human nature, Socrates. Given that they were firmly persuaded that thievery was beneficial, wouldn’t their first reaction to those setbacks be that there was not enough thievery going on? Wouldn’t they enact laws to encourage it still further?

SOCRATES: Alas, yes – at first. Yet, no matter how firmly they were persuaded, these setbacks would be problems in their lives, which they would want to solve. A few among them would eventually begin to suspect that increased thievery might not be the solution after all. So they would think about it more. They would have been convinced of the benefits of thievery by some explanation or other. Now they would try to explain why the supposed solution didn’t seem to be working. Eventually they would find an explanation that seemed better. So gradually they would persuade others of that – and so on until a majority again opposed thievery.

HERMES: Aha! So salvation would come about through persuasion.

SOCRATES: If you like. Thought, explanation and persuasion. And now they would understand better why thievery is harmful, through their new explanations.*

HERMES: By the way, the little story we have just imagined is exactly how Athens really does look, from my point of view.

SOCRATES: [somewhat resentfully] How you must laugh at us!

HERMES: Not at all, Athenian. As I said, I honour you. Now, let us consider what would happen if, instead of legalizing thievery, their error had been to ban debate. And to ban philosophy and politics and elections and that whole constellation of activities, and to consider them shameful.

SOCRATES: I see. That would have the effect of banning persuasion. And hence it would block off that path to salvation that we have discussed. This is a rare and deadly sort of error: it prevents itself from being undone.

HERMES: Or at least it makes salvation immensely more difficult, yes. This is what Sparta looks like, to me.

SOCRATES: I see. And to me too, now that you point it out. In the past I have often pondered the many differences between our two cities, for I must confess that there was – and still is – much that I admire about the Spartans. But I had never realized before now that those differences are all superficial. Beneath their evident virtues and vices, beneath even the fact that they are bitter enemies of Athens, Sparta is the victim – and the servant – of a profound evil. This is a momentous revelation, noble Apollo, better than a thousand declarations of the Oracle, and I cannot adequately express my gratitude.

HERMES: [Nods in acknowledgement.]

SOCRATES: I also see why you urge me always to bear human fallibility in mind. In fact, since you mentioned that some moral truths follow logically from epistemological considerations, I am now wondering whether they all do. Could it be that the moral imperative not to destroy the means of correcting mistakes is the only moral imperative? That all other moral truths follow from it?

HERMES: [Is silent.]

SOCRATES: As you wish. Now, in regard to Athens, and to what you were saying about epistemology: if our prospects for discovering new knowledge are so good, why were you stressing the unreliability of the senses?

HERMES: I was correcting your description of the quest for knowledge as striving to ‘see beyond what is easy to see’.

SOCRATES: I meant that metaphorically: ‘see’ in the sense of ‘understand’.

HERMES: Yes. Nevertheless, you have conceded that even those things that you thought were the easiest to see literally are in fact not easy to see at all without prior knowledge about them. In fact nothing is easy to see without prior knowledge. All knowledge of the world is hard to come by. Moreover –

SOCRATES: Moreover, it follows that we do not come by it through seeing. It does not flow into us through our senses.

HERMES: Exactly.

SOCRATES: Yet you say that objective knowledge is attainable. So, if it does not come to us through the senses, where it does come from?

HERMES: Suppose I were to tell you that all knowledge comes from persuasion.

SOCRATES: Persuasion again! Well, I would reply – with all due respect – that that makes no sense. Whoever persuades me of something must first have discovered it himself, so in such a case the relevant issue is where his knowledge came from –

HERMES: Quite right, unless –

SOCRATES: And, in any case, when I learn something through persuasion, it is coming to me via my senses.

HERMES: No, there you are mistaken. It only seems that way to you.


HERMES: Well, you are learning things from me now, aren’t you? Are they coming to you through your senses?

SOCRATES: Yes, of course they are. Oh – no they’re not. But that is only because you, a supernatural being, are bypassing my senses and sending me knowledge in a dream.


SOCRATES: I thought you said you’re not here to play debating tricks! Are you denying your own existence now? When sophists do that, I usually take them at their word and stop arguing with them.

HERMES: A policy that again bespeaks your wisdom, Socrates. But I have not denied my existence. I was only questioning what difference it makes whether I am real or not. Would it make you change your mind about anything that you have learned about epistemology during this conversation?

SOCRATES: Perhaps not . . .

HERMES: Perhaps not? Come now, Socrates, you were boasting earlier that you and your fellow citizens are always open to persuasion.

SOCRATES: Yes, I see.

HERMES: Now, if I am only a figment of your imagination, then who has persuaded you?

SOCRATES: Presumably I myself – unless this dream is coming neither from you nor from within myself, but from some other source . . .

HERMES: But did you not say that you are open to persuasion by anyone? If dreams emanate from an unknown source, what difference should that make? If they are persuasive, are you not honour-bound as an Athenian to accept them?

SOCRATES: It seems that I am. But what if a dream were to emanate from a malevolent source?

HERMES: That makes no fundamental difference either. Suppose that the source purports to tell you a fact. Then, if you suspect that the source is malevolent, you will try to understand what evil it is trying to perpetrate by telling you the alleged fact. But then, depending on your explanation, you may well decide to believe it anyway –

SOCRATES: I see. For instance, if an enemy announces that he is planning to kill me, I may well believe him despite his malevolence.

HERMES: Yes. Or you may not. And if your closest friend purports to tell you a fact, you may likewise wonder whether he has been misled by a malevolent third party – or is simply mistaken for any of countless reasons. Thus situations can easily arise in which you disbelieve your closest friend and believe your worst enemy. What matters in all cases is the explanation you create, within your own mind, for the facts, and for the observations and advice in question.

But the case here is simpler. As I said, I reveal no facts. I’m only making arguments.

SOCRATES: I see. I have no need to trust the source if the argument itself is persuasive. And no way of using any source unless I also have a persuasive argument.

Wait a moment – I’ve just realized something. You ‘reveal no facts’. But the god Apollo does reveal facts, hundreds of them every day, through the Oracle. Aha, I understand now. You are not Apollo, but a different god.

HERMES: [Is silent.]

SOCRATES: You’re evidently a god of knowledge . . . but several gods have an interest in knowledge. Athena herself does – but I can tell that you are not she.

HERMES: No you can’t.

SOCRATES: Yes I can. I don’t mean from your appearance. I mean I can infer it from the detached way you speak of Athens. So – I think you are Hermes. God of knowledge, and of messages, and of information flow –

HERMES: A fine thought. But, by the way, what makes you think that Apollo reveals facts through the Oracle?


HERMES: We have agreed that by ‘reveal’ we mean telling the supplicant something that he doesn’t yet know . . .

SOCRATES: Are all its replies just jokes and tricks?

HERMES: [Is silent.]

SOCRATES: As you wish, fleet Hermes. Then let me try to understand your argument about knowledge. I asked where knowledge comes from, and you directed my attention to this very dream. You asked whether it would make any difference to how I regard the knowledge I am learning from you if it turns out not to have been supernaturally inspired after all. And I had to agree that it would not. So am I to conclude that . . . all knowledge originates from the same source as dreams? Which is within ourselves?

HERMES: Of course it does. Do you remember what Xenophanes wrote just after he said that objective knowledge is attainable by humans?

SOCRATES: Yes. The passage continues:

But as for certain truth, no man has known it,

Nor will he know it; neither of the gods,

Nor yet of all things of which I speak.

And even if by chance he were to utter

The perfect truth, he would himself not know it –

So there he’s saying that, although objective knowledge is attainable, justified belief (‘certain truth’) is not.

HERMES: Yes, we’ve covered all that. But your answer is in the next line.

SOCRATES: ‘For all is but a woven web of guesses.’ Guesses!

HERMES: Yes. Conjectures.

SOCRATES: But wait! What about when knowledge does not come from guesswork – as when a god sends me a dream? What about when I simply hear ideas from other people? They may have guessed them, but I then obtain them merely by listening.

HERMES: You do not. In all those cases, you still have to guess in order to acquire the knowledge.


HERMES: Of course. Have you yourself not often been misunderstood, even by people trying hard to understand you?


HERMES: Have you, in turn, not often misunderstood what someone means, even when he is trying to tell you as clearly as he can?

SOCRATES: Indeed I have. Not least during this conversation!

HERMES: Well, this is not an attribute of philosophical ideas only, but of all ideas. Remember when you all got lost on your way here from the ship? And why?

SOCRATES: It was because – as we realized with hindsight – we completely misunderstood the directions given to us by the captain.

HERMES: So, when you got the wrong idea of what he meant, despite having listened attentively to every word he said, where did that wrong idea come from? Not from him, presumably . . .

SOCRATES: I see. It must come from within ourselves. It must be a guess. Though, until this moment, it had never even remotely occurred to me that I had been guessing.

HERMES: So why would you expect that anything different happens when you do understand someone correctly?

SOCRATES: I see. When we hear something being said, we guess what it means, without realizing what we are doing. That is beginning to make sense to me.

Except – guesswork isn’t knowledge!

HERMES: Indeed, most guesses are not new knowledge. Although guesswork is the origin of all knowledge, it is also a source of error, and therefore what happens to an idea after it has been guessed is crucial.

SOCRATES: So – let me combine that insight with what I know of criticism. A guess might come from a dream, or it might just be a wild speculation or random combination of ideas, or anything. But then we do not just accept it blindly or because we imagine it is ‘authorized’, or because we want it to be true. Instead we criticize it and try to discover its flaws.

HERMES: Yes. That is what you should do, at any rate.

SOCRATES: Then we try to remedy those flaws by altering the idea, or dropping it in favour of others – and the alterations and other ideas are themselves guesses. And are themselves criticized. Only when we fail in these attempts either to reject or to improve an idea do we provisionally accept it.

HERMES: That can work. Unfortunately, people do not always do what can work.

SOCRATES: Thank you, Hermes. It is exciting to learn of this single process through which all knowledge originates, whether it is our knowledge of a sea captain’s directions to Delphi, or knowledge of right and wrong that we have carefully refined for years, or theorems of arithmetic or geometry – or epistemology revealed to us by a god –

HERMES: It all comes from within, from conjecture and criticism.

SOCRATES: Wait! It comes from within, even if revealed by a god?

HERMES: And is just as fallible as ever. Yes. Your argument covers that case just like any other.

SOCRATES: Marvellous! But now – what about objects that we just experience in the natural world. We reach out and touch an object, and hence experience it out there. Surely that is a different kind of knowledge, a kind which – fallible or not – really does come from without, at least in the sense that our own experience is out there, at the location of the object.*

HERMES: You loved the idea that all those other different kinds of knowledge originate in the same way, and are improved in the same way. Why is ‘direct’ sensory experience an exception? What if it just seemsradically different?

SOCRATES: But surely you are now asking me to believe in a sort of all-encompassing conjuring trick, resembling the fanciful notion that the whole of life is really a dream. For it would mean that the sensation of touching an object does not happen where we experience it happening, namely in the hand that touches, but in the mind – which I believe is located somewhere in the brain. So all my sensations of touch are located inside my skull, where in reality nothing can touch while I still live. And whenever I think I am seeing a vast, brilliantly illuminated landscape, all that I am really experiencing is likewise located entirely inside my skull, where in reality it is constantly dark!

HERMES: Is that so absurd? Where do you think all the sights and sounds of this dream are located?

SOCRATES: I accept that they are indeed in my mind. But that is my point: most dreams portray things that are simply not there in the external reality. To portray things that are there is surely impossible without some input that does not come from the mind but from those things themselves.

HERMES: Well reasoned, Socrates. But is that input needed in the source of your dream, or only in your ongoing criticism of it?

SOCRATES: You mean that we first guess what is there, and then – what? – we test our guesses against the input from our senses?


SOCRATES: I see. And then we hone our guesses, and then fashion the best ones into a sort of waking dream of reality.*

HERMES: Yes. A waking dream that corresponds to reality. But there is more. It is a dream of which you then gain control. You do that by controlling the corresponding aspects of the external reality.

SOCRATES: [Gasps.] It is a wonderfully unified theory, and consistent, as far as I can tell. But am I really to accept that I myself – the thinking being that I call ‘I’ – has no direct knowledge of the physical world at all, but can only receive arcane hints of it through flickers and shadows that happen to impinge on my eyes and other senses? And that what I experience as reality is never more than a waking dream, composed of conjectures originating from within myself?

HERMES: Do you have an alternative explanation?

SOCRATES: No! And the more I contemplate this one, the more delighted I become. (A sensation of which I should beware! Yet I am also persuaded.) Everyone knows that man is the paragon of animals. But if this epistemology you tell me is true, then we are infinitely more marvellous creatures than that. Here we sit, for ever imprisoned in the dark, almost-sealed cave of our skull, guessing. We weave stories of an outside world – worlds, actually: a physical world, a moral world, a world of abstract geometrical shapes, and so on – but we are not satisfied with merely weaving, nor with mere stories. We want true explanations. So we seek explanations that remain robust when we test them against those flickers and shadows, and against each other, and against criteria of logic and reasonableness and everything else we can think of. And when we can change them no more, we have understood some objective truth. And, as if that were not enough, what we understand we then control. It is like magic, only real. We are like gods!

HERMES: Well, sometimes you discover some objective truth, and exert some control as a result. But often, when you think you have achieved any of that, you haven’t.

SOCRATES: Yes, yes. But having discovered some truths, can we not make better guesses and further criticisms and tests, and so understand more and control more, as Xenophanes says?


SOCRATES: So we are like gods!

HERMES: Somewhat. And yes, to answer your next question, you can indeed become ever more like gods in ever more ways, if you choose to. (Though you will always remain fallible.)

SOCRATES: Why on earth would we not choose to? Oh, I see: Sparta and suchlike . . .

HERMES: Yes. But also because some may argue that fallible gods are not a good thing –

SOCRATES: All right. But, if we choose to, are you saying that there is no upper bound to how much we can eventually understand, and control, and achieve?

HERMES: Funny you should ask that. Generations from now, a book will be written which will provide a compelling –

[At that moment there is a knocking at the door. SOCRATES glances towards the sound, and then back to where HERMES had been, but the god has vanished.]

CHAEREPHON: [through the door] Sorry to wake you, old chap, but I hear that unless we vacate these rooms before the house slaves arrive to clean them, they’re liable to charge us for another day.

SOCRATES: [Emerges, and motions CHAEREPHON’S SLAVE into the room to pack SOCRATES’ modest travelling bag.] Chaerephon – our trip hasn’t been wasted after all! I met Hermes.


SOCRATES: Yes, the god. In a dream, or maybe in person. Or maybe I just dreamed I met him. But it doesn’t matter, because, as he pointed out, it makes no difference.

CHAEREPHON: [Confused.] What? Why not?

SOCRATES: Because I learned a whole new branch of philosophy – and more!

[A group of Socrates’ COMPANIONS is approaching. Sprinting eagerly ahead of the rest is the teenage poet Aristocles, whom his friends call PLATO (‘the Broad’) because of his wrestler’s build.]

PLATO: Socrates! Good morning! Thank you again a thousandfold for letting me come on this pilgrimage! [Launches straight into philosophy without waiting for a reply.] But I was thinking last night: does it really count as a revelation if the Oracle tells us only what we already know? We already knew that there’s no one wiser than you, so I thought: shouldn’t we go back and demand a free question? But then I thought –

CHAEREPHON: Aristocles, Socrates has –

PLATO: No, wait! Don’t tell me the answer. Let me tell you my best guess first. So I thought: yes, we already knew he’s the wisest. And that he’s modest. But we didn’t know quite how modest. So that’s what the god revealed to us! That Socrates is so modest that he’d contradict even a god saying he’s wise.


PLATO: And another thing: we knew of Socrates’ excellence, but now Apollo has revealed it to the whole world.

CHAEREPHON: [under his breath] Then I wish ‘the whole world’ had chipped in for the fee.

PLATO: What was that? Did I get it right?

[SOCRATES draws breath to answer, but PLATO again continues.]

Oh, and Socrates, may I call you ‘Master’?


PLATO: Yes, yes, of course. Sorry. It’s just that I’ve been hanging out with some Spartan kids at the gymnasium, and they talk like that all the time. ‘My master says this. My master says that. My master does not permit . . . ’ and so on and so on. It got so that I became a bit envious that I don’t have a master myself, so –

COMPANION NO. 1: Eww, Plato!

PLATO: Yeah, but –

CHAEREPHON: [catching upSpartan kids? Aristocles, that is most improper. We are at war!

PLATO: Not here in Delphi we’re not. They’d never violate the sacred truce of the Oracle. They’re very devout, you know. Nice kids, despite their funny accents. We spoke a lot about wrestling – in between actual wrestling, that is. We were up all night, wrestling by candlelight. I’ve never done that before. They’re really good! Though they do sometimes cheat as well. [Smiles indulgently in recollection.] But, even so, I wasn’t going to let our city be humiliated. I won a few bouts for Athens, you’ll be glad to know. That was intense! They taught me some great moves. I can’t wait to try them out back home. For some reason none of them are much into poetry, though.

SOCRATES: They don’t honour poets in Sparta. Not living ones, anyway.

PLATO: Oh! Pity. I dashed off a poem in commemoration of our wrestling competition. Or rather, between the lines, it’s really about why Athens is better than Sparta. It’s a mathematical argument . . . Anyway, I’ve just sent a slave over to their compound to recite it to them, but if they don’t honour poets perhaps they won’t appreciate it. Oh well. It goes like this –

CHAEREPHON: Aristocles – last night Socrates was visited by the god Hermes!

PLATO: Wow! Why didn’t you call us, Socrates? That would have trumped even wrestling with Spartans!

SOCRATES: I couldn’t call anyone because it happened in a dream – or something. I’m not even sure that it was really the god. But, as he pointed out to me, it doesn’t matter.

PLATO: Why not? Oh, I guess that, once the experience is over, all that matters is what you learned from it. So, what did he want? I bet he wanted to poach you away from the cult of Apollo. Don’t do it, Socrates! Apollo is much better. Not that there’s anything wrong with Hermes, but he has no Oracle. And he’s not as cool –

CHAEREPHON: [shocked] Show some respect, Aristocles – to Socrates and to the gods!

SOCRATES: He is showing respect, Chaerephon, in his own way.

PLATO: [mystified] Of course I respect them, Chaerephon. And you know I’d literally worship Socrates if he’d let me. Oh, and I respect you too, old man. Greatly. I beg you to forgive me if I have offended you: I know I get too enthusiastic sometimes. [Pauses briefly.] But, Socrates – what did you ask the god and what did he reply?

SOCRATES: It wasn’t quite like that. He came to reveal to me a new branch of philosophy: epistemology – knowledge about knowledge, which also has implications for morality and other fields. Much of it I already knew, or partially knew in various special cases. But he gave me a god’s-eye overview, which was breathtaking. Interestingly, he mainly did this by asking me questions, and inviting me to think about certain things. It seems an effective technique – I may try it sometime.

PLATO: Tell us everything, Socrates! Start with the most interesting thing he asked, and your reply.

SOCRATES: Well – one thing he asked me to do was to imagine a ‘Spartan Socrates’.

PLATO: A Spartan what? Oh! I see! That must be whom the Oracle meant. How sneaky Apollo is! It’s the Spartan Socrates who’s the wisest man in the world – though only by the breadth of a hair, I’ll bet! But, being Spartan, he’s probably the greatest warrior as well. Awesome! Of course I know you were a great warrior in your day too, Socrates. But still – a Spartan Socrates! So are we going to Sparta to see him right away? Please!

CHAEREPHON: Aristocles – the war!

SOCRATES: Sorry to disappoint you, Aristocles, but it was a purely intellectual exercise. There is no ‘Spartan Socrates’. In fact I know of no Spartan philosophers at all. In a way, that is what much of my conversation with Hermes was about.

PLATO: Please tell us more.

[While saying this, PLATO gestures to his own SLAVE, who, well trained, tosses him a wax-covered writing tablet from a stack that he is carrying. PLATO catches it in one hand and pulls out a stylus.]

SOCRATES: At one stage, Hermes made me aware of the fundamental distinction between the Athenian approach to life and the Spartan. It is that –

PLATO: Wait! Let’s all guess! This sounds fascinating.

I’ll start – because this is basically what my poem was about. Well, the Spartan half of the riddle is easy: Sparta glories in war. And she values all the associated virtues such as courage, endurance and so on.

[The other COMPANIONS of Socrates murmur their assent.] We, on the other hand – well, we value everything, don’t we! Everything good, that is.

COMPANION NO. 1: Everything good? That seems a bit circular, Plato, unless you’re going to define ‘good’ in some way that’s independent of ‘what we Athenians value’. I think I can put it more elegantly: fighting, versus having something to fight for.

COMPANION NO. 2: Nice. But that’s basically ‘War versus Philosophy’, isn’t it?

PLATO: [taking mock offence] And poetry.

COMPANION NO. 3: Could it be that Athens, whose patron deity is female, represents the creative spirit in the world, while Sparta favours Ares, the god of bloodlust and slaughter, whom Athena defeated and humbled –

PLATO: No, no, they’re actually not that keen on Ares. They prefer Artemis. And, strangely enough, they also revere Athena. Did you know that?

CHAEREPHON: Speaking as an Athenian who is older than all of you and who has seen plenty of war, may I just say that it seems to me that Athens, despite all its glorious martial achievements, would be just as happy to lead a quiet life and be friends with all the Greeks, and not least with the Spartans. But unfortunately the Spartans like nothing better than to annoy us whenever they possibly can. Though I must admit that in that respect they are not especially worse than anyone else. Including our allies!

SOCRATES: Those are very interesting conjectures, all of which I think do capture aspects of the differences between the cities. And yet I suspect – and I may of course be mistaken –

PLATO: A Spartan Socrates wouldn’t be modest. Is that the difference?

SOCRATES: No. (By the way, I think that if anything, he would be.)

I suspect that we have all been labouring under a misconception about Sparta. Could it be that the Spartans do not seek war, as such, at all? At least, not since they conquered their neighbours, centuries ago, and made them helots. Perhaps, since then, they have acquired an entirely different concern that is of overriding importance to them; and perhaps they fight only when that concern is under threat.

COMPANION NO. 2: What is it? Keeping the helots down?

SOCRATES: No, that would be only a means, not the end in itself. I think that the god told me what their overarching concern is. And he also told me what ours is – though alas we also fight for all sorts of other reasons, of which we often repent.

Those two overarching concerns are these: we Athenians are concerned above all with improvement; the Spartans seek only – stasis. Two opposite objectives. If you think about it, I believe you’ll soon agree that this is the single source of all the myriad differences between the two cities.

PLATO: I never thought of it that way before, but I think I do agree. Let me try out the theory. Here’s one difference between the cities: Sparta has no philosophers. That’s because the job of a philosopher is to understand things better, which is a form of change, so they don’t want it. Another difference: they don’t honour living poets, only dead ones. Why? Because dead poets don’t write anything new, but live ones do. A third difference: their education system is insanely harsh; ours is famously lax. Why? Because they don’t want their kids to dare to question anything, so that they won’t ever think of changing anything. How am I doing?

SOCRATES: You are quick on the uptake as usual, Aristocles. However –

CHAEREPHON: Socrates, I think I know plenty of Athenians who do not seek improvement! We have many politicians who think they’re perfect. And many sophists who think they know everything.

SOCRATES: But what, specifically, do those politicians believe to be perfect? Their own grandiose plans for how to improve the city. Similarly, each sophist believes that everyone should adopt his ideas, which he sees as an improvement over everything that has been believed before. The laws and customs of Athens are set up to accommodate all these many rival ideas of perfection (as well as more modest proposals for improvement), to subject them to criticism, to winnow out from them what may be the few tiny seeds of truth, and to test out those that seem the most promising. Thus those myriad individuals who can conceive of no improvement of themselves nevertheless add up to a city that relentlessly seeks nothing else for itself, day and night.


SOCRATES: In Sparta there are no such politicians, and no such sophists. And no gadflies such as me, because any Spartan who did doubt or disapprove of the way things have always been done would keep it to himself. What few new ideas they have are intended to sustain the city more securely in its current state. As for war, I know that there are Spartans who glory in war, and would love to conquer and enslave the whole world, just as they once set out to conquer their neighbours. Yet the institutions of their city, and the deep assumptions that are built into the minds of even the hotheads, embody a visceral fear of any such step into the unknown. Perhaps it is significant that the statue of Ares that stands outside Sparta represents him chained, so that he will always be there to protect the city. Is that not the same as preventing the god of violence from breaking discipline? From being loosed upon the world to cause random mayhem, with its terrifying risk of change?

CHAEREPHON: Perhaps it is. In any case, I understand now, Socrates, how a city can have ‘overarching concerns’ that are not shared by all its citizens. However, I’m afraid I still don’t see how your theory accounts for the enmity between our cities. First of all, I cannot recall the Spartans ever objecting to our propensity to improve ourselves. Instead, they cite all sorts of specific grievances about how we are allegedly violating treaties, undermining their allies, plotting to build an empire on the mainland and so on. Second – not that I want to criticize the god, of course! –

SOCRATES: It is not impious to criticize the gods, Chaerephon, but rational. Hermes thinks so too, for what it’s worth . . .

PLATO: [Scribbles, ‘It is not impious to criticize gods.’]

CHAEREPHON: Well, even if the god is right about those two ‘overarching concerns’ of stasis and improvement, each city holds its respective concern only for itself. It has no ambition to impose it on anyone else. So, although Athens chooses to race forwards while Sparta chooses to tie itself down, and although these choices may logically be ‘opposite’, how can they possibly be a source of enmity?

SOCRATES: My guess is this. The very existence of Athens, however peaceful, is a deadly threat to Sparta’s stasis. And therefore, in the long run, the condition for the continued stasis of Sparta (which means its continued existence, as they see it) is the destruction of progress in Athens (which from our perspective would constitute the destruction of Athens).

CHAEREPHON: I still do not see specifically what the threat is.

SOCRATES: Well, suppose that in future both cities were to continue to succeed with their overarching concerns. The Spartans would stay exactly as they are now. But we Athenians are already the envy of other Greeks with our wealth and diverse achievements. What will happen when we improve further, and begin to outshine everyone in the world at everything? Spartans seldom travel or interact with foreigners, but they cannot keep themselves entirely in ignorance of developments elsewhere. Even going to war gives them some inkling of what life is like in other cities that are wealthier, and freer, than they. One day, some Spartan youths visiting Delphi will find that it is the Athenians who have the better ‘moves’ and the greater skill. And what if, in a generation or two, Athenian warriors have developed some better ‘moves’ on the battlefield?

PLATO: But, Socrates, even if this is true, the Spartans are unaware of it! So how can they fear it?

SOCRATES: They need no prescience. Do you think that a Spartan messenger, on reaching Athens, does not gasp in admiration like everyone else when he sees what stands on our Acropolis?* And, however much he may mutter (perhaps justly) about our hubris and irresponsibility, do you think that he does not reflect, on his way home, that his city can never and will never attract that sort of admiration from anyone? Do you think that the Spartan elders are not at this very moment worrying about the growing reputation of democracy in many cities, including some of their allies?

By the way, we ourselves should be at least as wary of democracy as I think the Spartans are of bloodlust and battle rage, for it is intrinsically as dangerous. We could not do without our democracy any more than the Spartans could do without their military training. And, just as they have moderated the destructiveness of bloodlust through their traditions of discipline and caution, we have moderated the destructiveness of democracy through our traditions of virtue, tolerance and liberty. We are utterly dependent on those traditions to keep our monster under control and on our side, just as the Spartans are dependent on theirtraditions to keep their monster from devouring them along with everyone else in sight. We might do well to put up a statue of democracy chained, to symbolize the fundamental safeguard of our city.

PLATO: [Scribbles, ‘Democracy is a monster, dangerous if not chained.’]

SOCRATES: The Spartans – and many others who do not understand us – must also be wondering every day how we Athenians can possibly be holding our own against them at the one thing in the world at which they are the best, namely warfare. This despite the fact that at the same time we are excelling more than ever at philosophy and poetry and drama and mathematics and architecture and all those other fields of human endeavour that the Spartans seldom if ever bother with.

PLATO: [Scribbles, ‘Spartans are world’s best at warfare but suck at everything else.’]

SOCRATES: They need not know the reason if they can see the fact. But the reason is: we can improve because we are constantly striving to; they hardly ever improve, because they are trying not to! That is the Achilles’ heel of Sparta.

PLATO: [Scribbles,Sparta’s Achilles’ heel is that they don’t improve.’] So all they need is philosophers. With philosophers, they’d be invincible!

SOCRATES: [Chuckles.] In a sense, that is the case, Aristocles. But –

PLATO: [Scribbles, ‘Socrates says that, with philosophers, Sparta would be invincible.’]

CHAEREPHON: [Worried.] Then should we really be discussing this here at a public inn? What if someone overhears and tells them the secret?

PLATO: [Scribbles‘Note to selfDon’t tell them!’]

SOCRATES: Don’t worry, old friend. If the Spartans in general were capable of understanding that ‘secret’, they’d have implemented it long ago – and there’d be no war between our cities. If some individual Spartan tried to advocate new philosophical ideas, he would soon find himself on trial for heresy or any number of other crimes.

PLATO: Unless . . .

SOCRATES: Unless what?

PLATO: Unless the one who had taken up philosophy was a king.

SOCRATES: Trust you to find the logical loophole, Aristocles. Theoretically you’re right, but in Sparta, even the kings are not allowed to change anything important. If one were to try, he would be deposed by the ephors.

PLATO: Well, they have two kings, five ephors and twenty-eight senators. So mathematics tells us that if only fifteen senators, three ephors and one king were to take up philosophy –

SOCRATES: [Laughs.] Yes, Aristocles. I concede. If the rulers of Sparta were to take up our style of philosophy, and were then seriously to embark upon criticizing and reforming their traditions –

PLATO: [Slightly distracted, scribbles, ‘Theorema king who’s a philosopher is the same as a philosopher who’s a king. So, what if a philosopher became king?’] Or perhaps it’s more likely that one benevolent king would have seized power –

SOCRATES: Whatever. If they succeeded in such reforms, then their city might indeed evolve into something truly great. But don’t hold your breath.

PLATO: [Scribbles, ‘Socrates says a city with a philosopher king would be truly great.’] I won’t hold my breath. But, in the long run, how shall we teach philosophy to kings, Socrates? [Scribbles, ‘Is the role of philosophers to educate kings?’]

SOCRATES: I’m not sure that philosophy should be the first step in the education of a leader. One must have something to philosophize about. He should know history, and literature, and arithmetic – and, perhaps above all, he should be familiar with the deepest knowledge we have, namely geometry.

PLATO: [Scribbles, ‘Let no one unversed in geometry enter here!’]

CHAEREPHON: Well, I judge a city by how it treats its philosophers.

SOCRATES: [Smiles.] An excellent criterion, Chaerephon, with which I had better not quibble! By the way, Aristocles, I am not in the least modest. And, to prove it, I can tell you that Hermes persuaded me that I am wise after all – at least in one respect that he especially values, namely that I am aware that justified belief is impossible and useless and undesirable.

PLATO: [Scribbles, ‘Socrates is the wisest man in the world because he is the only one who knows he has no knowledge, because genuine knowledge is impossible!’] Wait! Justified belief is impossible? Really? Are you sure?

SOCRATES: [Laughs loudly, while the OTHERS look on, puzzled.] Sorry, but it’s a somewhat perverse question, Aristocles.

PLATO: Oh! I see.

[Smiles ruefully, as do the OTHERS when they realize that Plato has just asked for a justification of the belief that one cannot justify beliefs.]

SOCRATES: No, I am not sure of anything. I never have been. But the god explained to me why that must be so, starting with the fallibility of the human mind and the unreliability of sensory experience.

PLATO: [Scribbles, ‘It’s only knowledge of the material world that’s impossible, useless and undesirable.’]

SOCRATES: He gave me a marvellous perspective on how we perceive the world. Each of your eyes is like a dark little cave, one on whose rear wall some stray shadows fall from outside. You spend your whole life at the back of that cave, able to see nothing but that rear wall, so you cannot see reality directly at all.

PLATO: [Scribbles, ‘It is as if we were prisoners, chained inside a cave and permitted to look only at the rear wall. We can never know the reality outside because we see only fleeting, distorted shadows of it.’]

[Note: Socrates is slightly improving on Hermes, and Plato has been increasingly misinterpreting Socrates.]

SOCRATES: He then went on to explain to me that objective knowledge is indeed possible: it comes from within! It begins as conjecture, and is then corrected by repeated cycles of criticism, including comparison with the evidence on our ‘wall’.

PLATO: [Scribbles, ‘The only true knowledge is that which comes from within. (How? Remembered from a previous life?)’]

SOCRATES: In this way, we frail and fallible humans can come to know objective reality – provided we use philosophically sound methods as I have described (which most people do not).

PLATO: [Scribbles, ‘We can come to know the true world beyond the illusory world of experience. But only by pursuing the kingly art of philosophy.’]

CHAEREPHON: Socrates, I think it was the god speaking to you, for I strongly feel that I have glimpsed a divine truth through you today. It will take me a long time to reorganize my ideas to take account of this new epistemology that he revealed to you. It seems a tremendously far-reaching, and important, subject.

SOCRATES: Indeed. I have some reorganizing to do myself.

PLATO: Socrates, you really ought to write all this down – together with all your other wisdom – for the benefit of the whole world, and posterity.

SOCRATES: No need, Aristocles. Posterity is right here, listening. Posterity is all of you, my friends. What is the point of writing down things that are going to be endlessly tinkered with and improved? Rather than make a permanent record of all my misconceptions as they are at a particular instant, I would rather offer them to others in two-way debate. That way I benefit from criticism and may even make improvements myself. Whatever is valuable will survive such debates and be passed on without any effort from me. Whatever is not valuable would only make me look a fool to future generations.

PLATO: If you say so, Master.

Since Socrates left us no writings, historians of ideas can only guess at what he really thought and taught, using the indirect evidence of his portrayal by Plato and a few others who were there at the time and whose accounts have survived. This is known as the ‘Socratic problem’, and is the source of much controversy. One common view is that the young Plato conveyed Socrates’ philosophy fairly faithfully, but that later he used the character of Socrates more as a vehicle for conveying his own views; that he did not even intend his dialogues to represent the real Socrates, but used them only as convenient ways of expressing arguments that have a to-and-fro form.

Perhaps I had better stress – in case it is not already obvious – that I am doing the same. I do not intend the above dialogue accurately to represent the philosophical opinions of the historical Socrates and Plato. I have set it at that moment in history, with those participants, because Socrates and his circle were among the foremost contributors to the ‘Golden Age of Athens’, which should have become a beginning of infinity but did not. And also because one thing that we do know about the ancient Greeks is that the philosophical problems they considered important have dominated Western philosophy ever since: How is knowledge obtained? How can we distinguish between true and false, right and wrong, reason and unreason? Which sorts of knowledge (moral, empirical, theological, mathematical, justified . . .) are possible, and which are mere chimeras? And so on. And therefore, although the theory of knowledge presented in the dialogue is largely that of the twentieth-century philosopher Karl Popper, together with some addenda of my own, I guess that Socrates would have understood and liked it. In some universes that were very like ours at the time, he thought of it himself.

I do want to make one indirect comment on the Socratic problem, though: we habitually underestimate the difficulty of communication – just as Socrates does at the end of the dialogue, when he assumes that each party to a debate necessarily knows what the other is saying, and Plato increasingly gets the wrong end of the stick. In reality, the communication of new ideas – even mundane ones like directions – depends on guesswork on the part of both the recipient and the communicator, and is inherently fallible. Hence there is no reason to expect that the young Plato, just because he was intelligent and highly educated, and by all accounts a near-worshipper of Socrates, made the fewest mistakes in conveying Socrates’ theories. On the contrary, the default assumption should be that misunderstandings are ubiquitous and that neither intelligence nor the intention to be accurate is any guarantee against them. It could easily be that the young Plato misunderstood everything that Socrates said to him, and that the older Plato gradually succeeded in understanding it, and is therefore the more reliable guide. Or it could be that Plato slipped ever further into misinterpretation, and into positive errors of his own. Evidence, argument and explanation are needed to distinguish between these and many other possibilities. It is a difficult task for historians. Objective knowledge, though attainable, is hard to attain.

All this holds as much for knowledge written down as for knowledge spoken in person. So there would still be a ‘Socratic problem’ even if Socrates had written books. Indeed, there is such a problem in regard to the prolific Plato, and sometimes even in regard to living philosophers. What does the philosopher mean by such and such a term or assertion? What problem is the assertion intended to solve, and how? These are not themselves philosophical problems. They are problems in the history of philosophy. Yet nearly all philosophers, especially academic ones, have devoted a great deal of their attention to them. Courses in philosophy place great weight on reading original texts, and commentaries on them, in order to understand the theories that were in the minds of various great philosophers.

This focus on history is odd, and is in marked contrast to all other academic disciplines (except perhaps history itself). For example, in all the physics courses that I took at university, both as an undergraduate and as a graduate student, I cannot recall a single instance where any original papers or books by the great physicists of old were studied or were even on the reading list. Only when a course touched upon very recent discoveries did we ever read the work of their discoverers. So we learned Einstein’s theory of relativity without ever hearing from Einstein; we knew Maxwell, Boltzmann, Schrödinger, Heisenberg and so on only as names. We read their theories in textbooks whose authors were physicists (not historians of physics) who themselves may well never have read the works of those pioneers.

Why? The immediate reason is that the original sources of scientific theories are almost never good sources. How could they be? All subsequent expositions are intended to be improvements on them, and some succeed, and improvements are cumulative. And there is a deeper reason. The originators of a fundamental new theory initially share many of the misconceptions of previous theories. They need to develop an understanding of how and why those theories are flawed, and how the new theory explains everything that they explained. But most people who subsequently learn the new theory have quite different concerns. Often they just want to take the theory for granted and use it to make predictions, or to understand some complex phenomenon in combination with other theories. Or they may want to understand nuances of it that have nothing to do with why it is superior to the old theories. Or they may want to improve it. But what they no longer care about is tracking down and definitively meeting every last objection that would naturally be made by someone thinking in terms of older, superseded theories. There is rarely any reason for scientists to address the obsolete problem-situations that motivated the great scientists of the past.

Historians of science, in contrast, must do precisely that – and they encounter much the same difficulties as the historians of philosophy who address the Socratic problem. Why, then, do scientists not encounter these difficulties when learning scientific theories? What is it that allows such theories to be communicated through chains of intermediaries with such apparent ease? What has happened to the ‘difficulty of communication’ that I stressed above?

The first, seemingly paradoxical, half of the answer is that, when they learn a theory, scientists are not interested in what the theory’s originator, or anyone else along the chain of communication, believed. When physicists read a textbook on the theory of relativity, their immediate objective is to learn the theory, and not the opinions of Einstein or of the textbook’s author. If that seems strange, imagine, for the sake of argument, that a historian were to discover that Einstein wrote his papers only as a joke, or at gunpoint, and was actually a lifelong believer in Kepler’s laws. This would be a bizarre and important discovery about the history of physics, and all the textbooks about that would have to be rewritten. But our knowledge of physics itself would be unaffected, and physics textbooks would not need any change at all.

The second half of the answer is that the reason why the scientists are trying to learn the theory, and also why they have such disregard for faithfulness to the original, is that they want to know how the world is. Crucially, this is the same objective that the originator of the theory had. If it is a good theory – if it is a superb theory, as the fundamental theories of physics nowadays are – then it is exceedingly hard to vary while still remaining a viable explanation. So the learners, through criticism of their initial guesses and with the help of their books, teachers and colleagues, seeking a viable explanation, will arrive at the same theory as the originator. That is how the theory manages to be passed faithfully from generation to generation, despite no one caring about its faithfulness one way or the other.

Slowly, and with many setbacks, the same is becoming true in non-scientific fields. The way to converge with each other is to converge upon the truth.