Plato · Theaetetus Θεαίτητος

Plato, Theaetetus 145a–147e: What is knowledge? Examples are not an answer

Socrates asks Theaetetus to say what knowledge is, since he is puzzled by it himself. Theaetetus answers by naming Theodorus' geometry and astronomy, harmony and calculation, and the crafts of the cobbler and other craftsmen. Socrates objects that he asked for what knowledge is, not for a list of kinds, just as a man asked what clay is should not reply with the clay of potters, oven-makers and brick-makers. He asks Theaetetus to try again, as he does with the problem of the roots and numbers.

Sections 145a–147e · 1322 words · click a number to copy its link

ΣΩ. νῦν δέ γʼ, οἶμαι, εἴ τι μέλει ἡμῖν τῆς τῶν προσώπων ὁμοιότητος, σκεπτέον εἰ γραφικὸς ὢν λέγει ἢ οὔ.

ΘΕΑΙ. δοκεῖ μοι.

ΣΩ. ἦ οὖν ζωγραφικὸς Θεόδωρος;

ΘΕΑΙ. οὔχ, ὅσον γέ με εἰδέναι.

ΣΩ. ἆρʼ οὐδὲ γεωμετρικός;

ΘΕΑΙ. πάντως δήπου, ὦ Σώκρατες.

ΣΩ. ἦ καὶ ἀστρονομικὸς καὶ λογιστικός τε καὶ μουσικὸς καὶ ὅσα παιδείας ἔχεται;

ΘΕΑΙ. ἔμοιγε δοκεῖ.

ΣΩ. εἰ μὲν ἄρα ἡμᾶς τοῦ σώματός τι ὁμοίους φησὶν εἶναι ἐπαινῶν πῃ ἢ ψέγων, οὐ πάνυ αὐτῷ ἄξιον τὸν νοῦν προσέχειν.

ΘΕΑΙ. ἴσως οὔ.

ΣΩ. τί δʼ εἰ ποτέρου τὴν ψυχὴν ἐπαινοῖ πρὸς ἀρετήν τε καὶ σοφίαν; ἆρʼ οὐκ ἄξιον τῷ μὲν ἀκούσαντι προθυμεῖσθαι ἀνασκέψασθαι τὸν ἐπαινεθέντα, τῷ δὲ προθύμως ἑαυτὸν ἐπιδεικνύναι;

ΘΕΑΙ. πάνυ μὲν οὖν, ὦ Σώκρατες.

ΣΩ. ὥρα τοίνυν, ὦ φίλε Θεαίτητε, σοὶ μὲν ἐπιδεικνύναι, ἐμοὶ δὲ σκοπεῖσθαι· ὡς εὖ ἴσθι ὅτι Θεόδωρος πολλοὺς δὴ πρός με ἐπαινέσας ξένους τε καὶ ἀστοὺς οὐδένα πω ἐπῄνεσεν ὡς σὲ νυνδή.

ΘΕΑΙ. εὖ ἂν ἔχοι, ὦ Σώκρατες· ἀλλʼ ὅρα μὴ παίζων ἔλεγεν.

ΣΩ. οὐχ οὗτος ὁ τρόπος Θεοδώρου· ἀλλὰ μὴ ἀναδύου τὰ ὡμολογημένα σκηπτόμενος παίζοντα λέγειν τόνδε, ἵνα μὴ καὶ ἀναγκασθῇ μαρτυρεῖν—πάντως γὰρ οὐδεὶς ἐπισκήψετʼ αὐτῷ—ἀλλὰ θαρρῶν ἔμμενε τῇ ὁμολογίᾳ.

ΘΕΑΙ. ἀλλὰ χρὴ ταῦτα ποιεῖν, εἰ σοὶ δοκεῖ.

ΣΩ. λέγε δή μοι· μανθάνεις που παρὰ Θεοδώρου γεωμετρίας ἄττα;

ΘΕΑΙ. ἔγωγε.

ΣΩ. καὶ τῶν περὶ ἀστρονομίαν τε καὶ ἁρμονίας καὶ λογισμούς;

ΘΕΑΙ. προθυμοῦμαί γε δή.

ΣΩ. καὶ γὰρ ἐγώ, ὦ παῖ, παρά τε τούτου καὶ παρʼ ἄλλων οὓς ἂν οἴωμαί τι τούτων ἐπαΐειν. ἀλλʼ ὅμως τὰ μὲν ἄλλα ἔχω περὶ αὐτὰ μετρίως, μικρὸν δέ τι ἀπορῶ ὃ μετὰ σοῦ τε καὶ τῶνδε σκεπτέον. καί μοι λέγε· ἆρʼ οὐ τὸ μανθάνειν ἐστὶν τὸ σοφώτερον γίγνεσθαι περὶ ὃ μανθάνει τις;

ΘΕΑΙ. πῶς γὰρ οὔ;

ΣΩ. σοφίᾳ δέ γʼ οἶμαι σοφοὶ οἱ σοφοί.

ΘΕΑΙ. ναί.

ΣΩ. τοῦτο δὲ μῶν διαφέρει τι ἐπιστήμης;

ΘΕΑΙ. τὸ ποῖον;

ΣΩ. ἡ σοφία. ἢ οὐχ ἅπερ ἐπιστήμονες ταῦτα καὶ σοφοί;

ΘΕΑΙ. τί μήν;

ΣΩ. ταὐτὸν ἄρα ἐπιστήμη καὶ σοφία;

ΘΕΑΙ. ναί.

SOC. But now, if we are concerned about the likeness of our faces, we must consider whether he who speaks is a painter, or not.

THEAET. I think we must.

SOC. Well, is Theodorus a painter?

THEAET. Not so far as I know.

SOC. Nor a geometrician, either?

THEAET. Oh yes, decidedly, Socrates.

SOC. And an astronomer, and an arithmetician, and a musician, and in general an educated man?

THEAET. I think so.

SOC. Well then, if he says, either in praise or blame, that we have some physical resemblance, it is not especially worth while to pay attention to him.

THEAET. Perhaps not.

SOC. But what if he should praise the soul of one of us for virtue and wisdom? Is it not worth while for the one who hears to examine eagerly the one who is praised, and for that one to exhibit his qualities with eagerness?

THEAET. Certainly, Socrates.

SOC. Then, my dear Theaetetus, this is just the time for you to exhibit your qualities and for me to examine them; for I assure you that Theodorus, though he has praised many foreigners and citizens to me, never praised anyone as he praised you just now.

THEAET. A good idea, Socrates; but make sure that he was not speaking in jest.

SOC. That is not Theodorus’s way. But do not seek to draw back from your agreement on the pretext that he is jesting, or he will be forced to testify under oath; for certainly no one will accuse him of perjury. Come, be courageous and hold to the agreement.

THEAET. I suppose I must, if you say so.

SOC. Now tell me; I suppose you learn some geometry from Theodorus?

THEAET. Yes.

SOC. And astronomy and harmony and arithmetic?

THEAET. I try hard to do so.

SOC. And so do I, my boy, from him and from any others who I think know anything about these things. But nevertheless, although in other respects I get on fairly well in them, yet I am in doubt about one little matter, which should be investigated with your help and that of these others. Tell me, is not learning growing wiser about that which one learns?

THEAET. Of course.

SOC. And the wise, I suppose, are wise by wisdom.

THEAET. Yes.

SOC. And does this differ at all from knowledge?

THEAET. Does what differ?

SOC. Wisdom. Or are not people wise in that of which they have knowledge?

THEAET. Of course.

SOC. Then knowledge and wisdom are the same thing?

THEAET. Yes.

ΣΩ. τοῦτʼ αὐτὸ τοίνυν ἐστὶν ὃ ἀπορῶ καὶ οὐ δύναμαι λαβεῖν ἱκανῶς παρʼ ἐμαυτῷ, ἐπιστήμη ὅτι ποτὲ τυγχάνει ὄν. ἆρʼ οὖν δὴ ἔχομεν λέγειν αὐτό; τί φατέ; τίς ἂν ἡμῶν πρῶτος εἴποι; ὁ δὲ ἁμαρτών, καὶ ὃς ἂν ἀεὶ ἁμαρτάνῃ, καθεδεῖται, ὥσπερ φασὶν οἱ παῖδες οἱ σφαιρίζοντες, ὄνος· ὃς δʼ ἂν περιγένηται ἀναμάρτητος, βασιλεύσει ἡμῶν καὶ ἐπιτάξει ὅτι ἂν βούληται ἀποκρίνεσθαι. τί σιγᾶτε; οὔ τί που, ὦ Θεόδωρε, ἐγὼ ὑπὸ φιλολογίας ἀγροικίζομαι, προθυμούμενος ἡμᾶς ποιῆσαι διαλέγεσθαι καὶ φίλους τε καὶ προσηγόρους ἀλλήλοις γίγνεσθαι;

ΘΕΟ. ἥκιστα μέν, ὦ Σώκρατες, τὸ τοιοῦτον ἂν εἴη ἄγροικον, ἀλλὰ τῶν μειρακίων τι κέλευέ σοι ἀποκρίνεσθαι· ἐγὼ μὲν γὰρ ἀήθης τῆς τοιαύτης διαλέκτου, καὶ οὐδʼ αὖ συνεθίζεσθαι ἡλικίαν ἔχω. τοῖσδε δὲ πρέποι τε ἂν τοῦτο καὶ πολὺ πλέον ἐπιδιδοῖεν· τῷ γὰρ ὄντι ἡ νεότης εἰς πᾶν ἐπίδοσιν ἔχει. ἀλλʼ, ὥσπερ ἤρξω, μὴ ἀφίεσο τοῦ Θεαιτήτου ἀλλʼ ἐρώτα.

ΣΩ. ἀκούεις δή, ὦ Θεαίτητε, ἃ λέγει Θεόδωρος, ᾧ ἀπειθεῖν, ὡς ἐγὼ οἶμαι, οὔτε σὺ ἐθελήσεις, οὔτε θέμις περὶ τὰ τοιαῦτα ἀνδρὶ σοφῷ ἐπιτάττοντι νεώτερον ἀπειθεῖν. ἀλλʼ εὖ καὶ γενναίως εἰπέ· τί σοι δοκεῖ εἶναι ἐπιστήμη;

ΘΕΑΙ. ἀλλὰ χρή, ὦ Σώκρατες, ἐπειδήπερ ὑμεῖς κελεύετε. πάντως γάρ, ἄν τι καὶ ἁμάρτω, ἐπανορθώσετε.

ΣΩ. πάνυ μὲν οὖν, ἄνπερ γε οἷοί τε ὦμεν.

ΘΕΑΙ. δοκεῖ τοίνυν μοι καὶ ἃ παρὰ Θεοδώρου ἄν τις μάθοι ἐπιστῆμαι εἶναι, γεωμετρία τε καὶ ἃς νυνδὴ σὺ διῆλθες, καὶ αὖ σκυτοτομική τε καὶ αἱ τῶν ἄλλων δημιουργῶν τέχναι, πᾶσαί τε καὶ ἑκάστη τούτων, οὐκ ἄλλο τι ἢ ἐπιστήμη εἶναι.

ΣΩ. γενναίως γε καὶ φιλοδώρως, ὦ φίλε, ἓν αἰτηθεὶς πολλὰ δίδως καὶ ποικίλα ἀντὶ ἁπλοῦ.

ΘΕΑΙ. πῶς τί τοῦτο λέγεις, ὦ Σώκρατες;

ΣΩ. ἴσως μὲν οὐδέν· ὃ μέντοι οἶμαι, φράσω. ὅταν λέγῃς σκυτικήν, μή τι ἄλλο φράζεις ἢ ἐπιστήμην ὑποδημάτων ἐργασίας;

ΘΕΑΙ. οὐδέν.

ΣΩ. τί δʼ ὅταν τεκτονικήν; μή τι ἄλλο ἢ ἐπιστήμην τῆς τῶν ξυλίνων σκευῶν ἐργασίας;

ΘΕΑΙ. οὐδὲ τοῦτο.

ΣΩ. οὐκοῦν ἐν ἀμφοῖν, οὗ ἑκατέρα ἐπιστήμη, τοῦτο ὁρίζεις;

ΘΕΑΙ. ναί.

ΣΩ. τὸ δέ γʼ ἐρωτηθέν, ὦ Θεαίτητε, οὐ τοῦτο ἦν, τίνων ἡ ἐπιστήμη, οὐδὲ ὁπόσαι τινές· οὐ γὰρ ἀριθμῆσαι αὐτὰς βουλόμενοι ἠρόμεθα ἀλλὰ γνῶναι ἐπιστήμην αὐτὸ ὅτι ποτʼ ἐστίν. ἢ οὐδὲν λέγω;

ΘΕΑΙ. πάνυ μὲν οὖν ὀρθῶς.

SOC. Well, it is just this that I am in doubt about and cannot fully grasp by my own efforts—what knowledge really is. Can we tell that? What do you say? Who of us will speak first? And he who fails, and whoever fails in turn, shall go and sit down and be donkey, as the children say when they play ball; and whoever gets through without failing shall be our king and shall order us to answer any questions he pleases. Why are you silent? I hope, Theodorus, I am not rude, through my love of discussion and my eagerness to make us converse and show ourselves friends and ready to talk to one another.

THEO. That sort of thing would not be at all rude, Socrates; but tell one of the youths to answer your questions; for I am unused to such conversation and, moreover, I am not of an age to accustom myself to it. But that would be fitting for these young men, and they would improve much more than I; for the fact is, youth admits of improvement in every way. Come, question Theaetetus as you began to do, and do not let him off.

SOC. Well, Theaetetus, you hear what Theodorus says, and I think you will not wish to disobey him, nor is it right for a young person to disobey a wise man when he gives instructions about such matters. Come, speak up well and nobly. What do you think knowledge is?

THEAET. Well, Socrates, I must, since you bid me. For, if I make a mistake, you are sure to set me right.

SOC. Certainly, if we can.

THEAET. Well then, I think the things one might learn from Theodorus are knowledge—geometry and all the things you spoke of just now—and also cobblery and the other craftsmen’s arts; each and all of these are nothing else but knowledge.

SOC. You are noble and generous, my friend, for when you are asked for one thing you give many, and a variety of things instead of a simple answer.

THEAET. What do you mean by that, Socrates?

SOC. Nothing, perhaps; but I will tell you what I think I mean. When you say “cobblery” you speak of nothing else than the art of making shoes, do you?

THEAET. Nothing else.

SOC. And when you say “carpentry”? Do you mean anything else than the art of making wooden furnishings?

THEAET. Nothing else by that, either.

SOC. Then in both cases you define that to which each form of knowledge belongs?

THEAET. Yes.

SOC. But the question, Theaetetus, was not to what knowledge belongs, nor how many the forms of knowledge are; for we did not wish to number them, but to find out what knowledge itself really is. Or is there nothing in what I say?

THEAET. Nay, you are quite right.

ΣΩ. σκέψαι δὴ καὶ τόδε. εἴ τις ἡμᾶς τῶν φαύλων τι καὶ προχείρων ἔροιτο, οἷον περὶ πηλοῦ ὅτι ποτʼ ἐστίν, εἰ ἀποκριναίμεθα αὐτῷ πηλὸς ὁ τῶν χυτρέων καὶ πηλὸς ὁ τῶν ἰπνοπλαθῶν καὶ πηλὸς ὁ τῶν πλινθουργῶν, οὐκ ἂν γελοῖοι εἶμεν;

ΘΕΑΙ. ἴσως.

ΣΩ. πρῶτον μέν γέ που οἰόμενοι συνιέναι ἐκ τῆς ἡμετέρας ἀποκρίσεως τὸν ἐρωτῶντα, ὅταν εἴπωμεν πηλός, εἴτε ὁ τῶν κοροπλαθῶν προσθέντες εἴτε ἄλλων ὡντινωνοῦν δημιουργῶν. ἢ οἴει τίς τι συνίησίν τινος ὄνομα, ὃ μὴ οἶδεν τί ἐστιν;

ΘΕΑΙ. οὐδαμῶς.

ΣΩ. οὐδʼ ἄρα ἐπιστήμην ὑποδημάτων συνίησιν ὁ ἐπιστήμην μὴ εἰδώς.

ΘΕΑΙ. οὐ γάρ.

ΣΩ. σκυτικὴν ἄρα οὐ συνίησιν ὃς ἂν ἐπιστήμην ἀγνοῇ, οὐδέ τινα ἄλλην τέχνην.

ΘΕΑΙ. ἔστιν οὕτως.

ΣΩ. γελοία ἄρα ἡ ἀπόκρισις τῷ ἐρωτηθέντι ἐπιστήμη τί ἐστιν, ὅταν ἀποκρίνηται τέχνης τινὸς ὄνομα. τινὸς γὰρ ἐπιστήμην ἀποκρίνεται οὐ τοῦτʼ ἐρωτηθείς.

ΘΕΑΙ. ἔοικεν.

ΣΩ. ἔπειτά γέ που ἐξὸν φαύλως καὶ βραχέως ἀποκρίνασθαι περιέρχεται ἀπέραντον ὁδόν. οἷον καὶ ἐν τῇ τοῦ πηλοῦ ἐρωτήσει φαῦλόν που καὶ ἁπλοῦν εἰπεῖν ὅτι γῆ ὑγρῷ φυραθεῖσα πηλὸς ἂν εἴη, τὸ δʼ ὅτου ἐᾶν χαίρειν.

ΘΕΑΙ. ῥᾴδιον, ὦ Σώκρατες, νῦν γε οὕτω φαίνεται· ἀτὰρ κινδυνεύεις ἐρωτᾶν οἷον καὶ αὐτοῖς ἡμῖν ἔναγχος εἰσῆλθε διαλεγομένοις, ἐμοί τε καὶ τῷ σῷ ὁμωνύμῳ τούτῳ Σωκράτει.

ΣΩ. τὸ ποῖον δή, ὦ Θεαίτητε;

ΘΕΑΙ. περὶ δυνάμεών τι ἡμῖν Θεόδωρος ὅδε ἔγραφε, τῆς τε τρίποδος πέρι καὶ πεντέποδος [ἀποφαίνων] ὅτι μήκει οὐ σύμμετροι τῇ ποδιαίᾳ, καὶ οὕτω κατὰ μίαν ἑκάστην προαιρούμενος μέχρι τῆς ἑπτακαιδεκάποδος· ἐν δὲ ταύτῃ πως ἐνέσχετο. ἡμῖν οὖν εἰσῆλθέ τι τοιοῦτον, ἐπειδὴ ἄπειροι τὸ πλῆθος αἱ δυνάμεις ἐφαίνοντο, πειραθῆναι συλλαβεῖν εἰς ἕν, ὅτῳ πάσας ταύτας προσαγορεύσομεν τὰς δυνάμεις.

ΣΩ. ἦ καὶ ηὕρετέ τι τοιοῦτον;

ΘΕΑΙ. ἔμοιγε δοκοῦμεν· σκόπει δὲ καὶ σύ.

ΣΩ. λέγε.

ΘΕΑΙ. τὸν ἀριθμὸν πάντα δίχα διελάβομεν· τὸν μὲν δυνάμενον ἴσον ἰσάκις γίγνεσθαι τῷ τετραγώνῳ τὸ σχῆμα ἀπεικάσαντες τετράγωνόν τε καὶ ἰσόπλευρον προσείπομεν.

ΣΩ. καὶ εὖ γε.

SOC. Take this example. If anyone should ask us about some common everyday thing, for instance, what clay is, and we should reply that it is the potters’ clay and the oven makers’ clay and the brickmakers’ clay, should we not be ridiculous?

THEAET. Perhaps.

SOC. Yes in the first place for assuming that the questioner can understand from our answer what clay is, when we say “clay,” no matter whether we add “the image-makers’” or any other craftsmen’s. Or does anyone, do you think, understand the name of anything when he does not know what the thing is?

THEAET. By no means.

SOC. Then he does not understand knowledge of shoes if he does not know knowledge.

THEAET. No.

SOC. Then he who is ignorant of knowledge does not understand cobblery or any other art.

THEAET. That is true.

SOC. Then it is a ridiculous answer to the question “what is knowledge?” when we give the name of some art; for we give in our answer something that knowledge belongs to, when that was not what we were asked.

THEAET. So it seems.

SOC. Secondly, when we might have given a short, everyday answer, we go an interminable distance round; for instance, in the question about clay, the everyday, simple thing would be to say “clay is earth mixed with moisture” without regard to whose clay it is.

THEAET. It seems easy just now, Socrates, as you put it; but you are probably asking the kind of thing that came up among us lately when your namesake, Socrates here, and I were talking together.

SOC. What kind of thing was that, Theaetetus?

THEAET. Theodorus here was drawing some figures for us in illustration of roots, showing that squares containing three square feet and five square feet are not commensurable in length with the unit of the foot, and so, selecting each one in its turn up to the square containing seventeen square feet and at that he stopped. Now it occurred to us, since the number of roots appeared to be infinite, to try to collect them under one name, by which we could henceforth call all the roots.

SOC. And did you find such a name?

THEAET. I think we did. But see if you agree.

SOC. Speak on.

THEAET. We divided all number into two classes. The one, the numbers which can be formed by multiplying equal factors, we represented by the shape of the square and called square or equilateral numbers.

SOC. Well done!

English translation by Harold North Fowler (1921). Original text: Harold North Fowler (trans.), Plato VII: Theaetetus, Sophist, Loeb Classical Library, Cambridge, MA: Harvard University Press; London: William Heinemann, 1921; Greek text: John Burnet, Platonis Opera, Oxford Classical Texts (as digitised by Perseus).

Greek text and translation from the Perseus Digital Library, Tufts University, CC BY-SA 4.0 (Perseus Digital Library); translation public domain. Introductions, summaries and notes © GreekMythology.com.