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1108 lines
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*****Project Gutenberg's Etext of the Second Story of Meno*****
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**A Socratic Dialogue Proving the Square Root of 2 Irrational**
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Second Story of Meno (C)1995
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MENO II
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A CONTINUATION OF SOCRATES' DIALOGUE WITH MENO
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IN WHICH THE BOY PROVES ROOT 2 IS IRRATIONAL
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A Millennium Fulcrum Edition [Copyright 1995]
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Socrates: Well, here we are at the appointed time, Meno.
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Meno: Yes, and it looks like a fine day for it, too.
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Socrates: And I see our serving boy is also here.
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Boy: Yes, I am, and ready to do your bidding.
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Socrates: Wonderful. Now, Meno, I want you to be on your guard,
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as you were the other day, to insure that I teach nothing to the boy,
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but rather pull out of his mind the premises which are already there.
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Meno: I shall do my best, Socrates.
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Socrates: I can ask more of no man, Meno, and I am certain that
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you will do well, and I hope I will give you no call to halt me
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in my saying if I should say too much, in which you would feel I
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was actually teaching the boy the answer to this riddle.
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Meno: No, Socrates, I don't think I will have to call you on
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anything you might say today, for the most wondrously learned men
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of the group of Pythagoras have spent many hours, weeks, and even
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months and years toiling in their manner to arrive at the mystic
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solutions to the puzzles formed by the simple squares with which
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we worked the other day. Therefore, I am certain to regain my
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virtue, which I lost the other day, when I was so steadfastly
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proven by you to be in error in my statement that the root of a
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square with an area of two square feet was beyond this boy,
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who is a fine boy, whom we must make to understand that he should
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do his best here, and not feel that he has done any wrongness by
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causing me to lose my virtue to you the other day.
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Socrates: Meno, my friend, it is my opinion, and I hope it will
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soon be yours, that your virtue was increased the other day,
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rather than decreased.
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Meno: I fail to see how, when I was humiliated by seeing
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this young boy, of modest education, arrive in minutes at the
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highest mystic levels of the magic of the Pythagoreans.
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Most of all when I wagered as many dinners as you could eat
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at my house that this could not be the case.
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Socrates: First, friend Meno, let me assure you that I will
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promise never to eat you out of house and home, not that I could
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if I tried, for my tastes are simple and your wallet is large.
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Nevertheless, Meno, my friend, I would hasten to add that I will
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promise, if you like, not to ever come to your table uninvited.
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As a second reason you and your virtue should feel better after
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the events of the other day, because you were in error before,
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but are less in error now. And the path to virtue, at least one
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aspect of the path to virtue, is in finding and correcting error.
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Meno: Socrates, you know you are always welcome at my table,
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except when I am suffering from my ulcer, which you aggravate
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greatly, or at time when I am entertaining the highest nobles
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of the land, and you would appear out of place in your clothing.
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(Socrates was known for his simple attire, and for wearing his
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garments over and over till they wore out. However, the only
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surviving example of his writing is a laundry list, so we know he
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kept his clothes clean and somewhat presentable, though simple)
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Socrates: I would hope you would have me over because I was
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a good influence on your development, than for any other reason.
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I notice you did not respond to my claim to have increased
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your virtue, through the exorcism of your error.
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Meno: Well Socrates, you know that it is not always the
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easiest thing to give up one's ways, even though one has found
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them to be in error. Therefore, please forgive me if I am not
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sounding as grateful as you would like for your lessons.
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Socrates: The easier one finds it to give up the ways of error,
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the easier it is to replace the error with that which we hope
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is not in error. Is this not the way to virtue?
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Meno: Yes, Socrates, and you know the path is hard,
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and that we often stumble and fall.
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Socrates: Yes, but is it not true that we stumble and fall
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over the obstacles which we make for ourselves to trip over?
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Meno: Certainly that is most true, Socrates, in some cases.
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Socrates: Well, then, let us proceed, for I see the hour is upon us
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when I do my best thinking, and that hour shall be passed soon,
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and hopefully with it shall pass a bit of your ignorance.
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Meno: Well said, Socrates. I am with you.
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Socrates: And shall have we a wager on the events of today?
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Meno: Certainly, Socrates.
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Socrates: And what shall you wager against this boy proving
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that the length of the root of a square with an area of two
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square feet, cannot be made by the ratio of two whole numbers?
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Meno: You may have anything it is in my power to give,
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unless it cause harm to myself or to another to give it.
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Socrates: Well said, my friend Meno, and I shall leave it at
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that. And what shall I offer you as a return wager?
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Meno: Well, the easiest thing which comes to mind is to
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wager all those dinners you won from me the other day.
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Socrates: Very well, so be it.
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Meno: Now Socrates, since you are my friend, I must give you
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this friendly warning: you know that the Pythagoreans jealously
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guard their secrets with secret meetings, protected by secret
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handshakes, secret signs, passwords, and all that, do you not?
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Socrates: I have heard as much, friend Meno.
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Meno: Then be sure that they will seek revenge upon you for
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demystifying the ideas and concepts which they worked so long and
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hard and secretly to create and protect; for they are a jealous lot
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in the extreme, hiding in mountain caves, which are hardly fit
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to be called monasteries by even the most hardened monk.
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Socrates: I take your meaning, friend Meno, and thank you
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for your consideration, but I think that if I lose, that they
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will not bother me, and if I win, it will appear so simple to
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everyone, that if would be sheerest folly for anyone to make
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even the smallest gesture to protect its fallen mystic secrecy.
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Besides, I have a citizen's responsibility to Athens and to all
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Athenians to do my best to protect them and enlighten them.
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Meno: Very well, Socrates. Please do not ever say that I did not
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try to warn you, especially after they have nailed you to a cross
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in a public place, where anyone and everyone could hear you say
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that the fault of this lay in my name.
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Socrates: Do not worry, friend Meno, for if I were not
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to show this simple feat of logic to you, I should just walk
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down the street and find someone else, though not someone whose
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company and conversation I should enjoy as much as yours.
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Meno: Thank you, friend Socrates.
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Socrates: Now, boy, do you remember me, and the squares with
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which we worked and played the other day?
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Boy: Yes, sir, Socrates.
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Socrates: Please, Meno, instruct the boy to merely call me
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by my name, as does everyone else. Calling me "sir" merely puts
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me off my mental stride, and, besides, it will create a greater
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distance between me and the boy.
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Meno: You heard what Socrates, said, boy. Can you do it?
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Meno: Yes, sir. (Turning to Socrates) You know I like you
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very much, and that I call you "sir" not only out of relation of
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our positions in society, but also because of my true respect and
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admiration, especially after the events of the other day.
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Socrates: Yes, boy. And I will try to live up to your
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expectations. (turning to Meno) Would you allow some reward for
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the boy, as well as that which is for myself, if he should prove
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to your satisfaction that the square root of two is irrational?
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Meno: Certainly, Socrates.
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Socrates: (taking the boy aside) What would you like
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the most in the whole world, boy?
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Boy: You mean anything?
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Socrates: Well, I can't guarantee to get it for you, but at
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least I can ask it, and it shouldn't hurt to ask; and besides,
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as you should know, it is very hard to expect someone to give
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you what you want, if you never let them know you want it.
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Boy: Well, Socrates . . . you know what I would want.
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Socrates: Do I?
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Boy: Better than I knew the square root of two the other day.
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Socrates: You want to be a free man, then, and a citizen.
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Boy: (looking down) Yes.
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Socrates: Don't look down, then, for that is an admirable
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desire for one to have, and speaks highly of him who has it.
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I will speak to Meno, while you hold your tongue.
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Boy: Yes, Socrates. (bows to kiss his hand, Socrates turns)
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Socrates: Friend Meno, how hard do you think it will be for
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this boy to prove the irrationality of the square root of two?
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Meno: You know that I think it is impossible, Socrates.
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Socrates: Well, how long did it take the Pythagoreans?
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Meno: I should think it took them years.
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Socrates: And how many of them were there?
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Meno: Quite a few, though not all worked equally, and some
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hardly at all, for they were most interested in triangles of the
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right and virtuous variety, and not in squares and their roots.
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Socrates: Can you give me an estimate?
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Meno: No, I can't say that I can. I am sorry, Socrates.
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Socrates: No problem, would you accept five thinkers as an estimate.
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Meno: I think that should be fair.
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Socrates: And shall we assume they worked for two years,
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that is the smallest number which retains the plural,
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and our assumption was that they worked for years.
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Meno: Two years is indeed acceptable to me, Socrates.
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Socrates: Very well then, Meno, it would appear that the
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Pythagoreans spent 10 total years of thinking time to solve the
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riddles of the square root of two.
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Meno: I agree.
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Socrates: And would you like to hire the Pythagoreans
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to run your household, Meno?
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Meno: Surely I would, Socrates, if they were only for hire,
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but, as you well know, they are a secret lot, and hire to no one.
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Socrates: Well, if I could get you one, perhaps one of the
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best of them, in fact the leader of the group that solved the
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square root of two, would you not hire him, and at high wages?
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Meno: Certainly, Socrates. I'd be a fool not to.
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Socrates: And you would put him in charge of your house.
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Meno: And all my lands, too, Socrates.
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Socrates: Possibly. Then I would like to propose, that if
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this boy should solve the proof of the square root of two being
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irrational, in the next few hours of our discussion, that he be
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given wages equal to those due to your most highly placed servant
|
|
for ten years of service, as he shall perform ten years service
|
|
for you in the next few hours, should he succeed.
|
|
|
|
Meno: That sound quite fair, Socrates, I like your logic.
|
|
|
|
Socrates: (the boy tugs his tunic, to complain that he wants
|
|
his freedom, not a mere bucket of gold) Hush, boy, did you not
|
|
promise to hold your tongue?
|
|
|
|
Boy: Yes, Socrates, but . . . .
|
|
|
|
Socrates: (turning to Meno) And, of course, with the
|
|
monetary rewards for such a position, go all the rest of it.
|
|
|
|
Meno: Of course, Socrates. I never thought to cheat you.
|
|
|
|
Socrates: I know that, friend Meno, but I merely ask for the
|
|
boy's sake, who is not used to hearing about high finance and
|
|
the powers and rank which accompany such things.
|
|
|
|
Meno: Of course, Socrates. Shall I tell the boy what he
|
|
shall receive?
|
|
|
|
Socrates: You are very kind to do so, my friend Meno.
|
|
|
|
Meno: (turns to the boy) You are aware that a servant may
|
|
not own the amount of gold I would have to give you,
|
|
should you win the day?
|
|
|
|
Boy: Yes, sir.
|
|
|
|
Meno: Therefore, I would have to give to you the freedom to
|
|
own the money, before I could give you the money, would I not?
|
|
|
|
Boy: Yes, sir.
|
|
|
|
Meno: And in giving you freedom, I would be remiss if I did
|
|
not give you a job and a coming out party of equal position
|
|
with your wealth, would I not?
|
|
|
|
Boy: I can't really say, sir, though I suppose so.
|
|
|
|
Meno: You suppose correctly. I will feed you for a week of
|
|
partying, and dress you in the finest garments, while you are
|
|
introduced to the finest ladies and gentlemen of Athens, from
|
|
whom you are free to select for your interests as friends,
|
|
business partners, social acquaintances, connections, and perhaps
|
|
even a wife, should you find someone you like for that. Do you
|
|
now understand that there is nothing I would leave out that you
|
|
would have to ask for, or that if you did have to ask, I would
|
|
give it immediately, and ask your forgiveness for my error?
|
|
|
|
Boy: It is hard to understand, but I take your word.
|
|
|
|
Socrates: Now don't let this all go to your head, boy.
|
|
This is something you could have figured out for yourself,
|
|
if you had applied your mind to it as you did to squares
|
|
the other day. Can you do as well, today?
|
|
|
|
Boy: I should think and hope so, friend Socrates, for I see you
|
|
are indeed my friend, and I should hope I am more capable today,
|
|
for having learned some the other day.
|
|
|
|
Socrates: We shall see, boy. Let us on to the test.
|
|
Now you remember the squares we dealt with the other day.
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: And the one particular square on the diagonal we made,
|
|
whose area was two, do you remember that one?
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: And you remember that the length of the side of a square,
|
|
when multiplied by itself, yields the area of the square.
|
|
|
|
Boy: Everyone at school knows that, Socrates.
|
|
|
|
Socrates: Well, maybe. However, it is about that side,
|
|
which when multiplied time itself yields an area of two,
|
|
that I would like to speak further today. How is that with you?
|
|
|
|
Boy: That is fine, Socrates. I remember that line,
|
|
and I sort of liked it the best, if you know what I mean.
|
|
|
|
Socrates: Good, then we should have a great time.
|
|
Do you know how long that line is, boy?
|
|
|
|
Boy: Well, I know that you both thought it wise when I said
|
|
it was of a length which when made a square of, yielded a square
|
|
with an area of two, so I suppose I should answer that way.
|
|
|
|
Socrates: And a good answer it is, too. We are going to
|
|
make it an even better answer as we proceed.
|
|
|
|
Boy: Good.
|
|
|
|
Socrates: Do you remember when you tripped up and fell on
|
|
your face the other day, when you thought that the square of area
|
|
nine was actually a square of area eight?
|
|
|
|
Boy: Oh yes, Socrates! And I am sorely ashamed, because I still
|
|
do not know enough to make sure I never make such an error again,
|
|
and therefore I know my virtue and rightness are lacking.
|
|
|
|
Socrates: They are not lacking so much that they cannot be improved,
|
|
are they boy?
|
|
|
|
Boy: I should hope and pray not.
|
|
|
|
Socrates: Well today, you are going to tell us some things
|
|
about that number, which when multiplied by itself gives us two.
|
|
|
|
Boy: I will tell you everything I know, or think I know,
|
|
Socrates, and hope that I am correct or can be corrected.
|
|
|
|
Socrates: To Meno, surely he is a fine boy, eh Meno?
|
|
|
|
Meno: Yes, I am proud to own him, but I don't see how he
|
|
can be smart enough to do the work today that would take a
|
|
Pythagorean monk ten years of cloistered life to accomplish.
|
|
|
|
Socrates: We shall see. Boy, you are doing fine. I think I
|
|
could even make a scholar of you, though I fear you might turn to
|
|
wine and women with your new found wealth, if you succeed, rather
|
|
than continue to polish the wit which should get you that reward.
|
|
|
|
Boy: I don't think I would want to spend that much time with
|
|
women or with wine, Socrates.
|
|
|
|
Socrates: You will find something, no doubt. So, back to
|
|
the number which when square gives us two. What can we say about
|
|
such a number? Is it odd or even? Well it would have to be a
|
|
whole number to be one of those, would it not, and we saw the
|
|
other day what happens to whole numbers when they are squared?
|
|
They give us 1,4,9 and 16 as square areas, did they not?
|
|
|
|
Boy: Yes, Socrates, though I remember thinking that there
|
|
should have been a number which would give eight, Socrates?
|
|
|
|
Socrates: I think we shall find one, if we keep searching.
|
|
Now, this number, do you remember if it had to be larger or
|
|
smaller than one?
|
|
|
|
Boy: Larger, Socrates. For one squared gives only an area
|
|
of one, and we need and area of two, which is larger.
|
|
|
|
Socrates: Good. And what of two?
|
|
|
|
Boy: Two gives a square of four, which is too large.
|
|
|
|
Socrates: Fine. So the square root of two is smaller than
|
|
the side two which is the root of four, and larger than the side
|
|
one which yields one?
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: (Turning to Meno) So now he is as far as most of
|
|
us get in determining the magnitude of the square root of two?
|
|
And getting farther is largely a matter of guesswork, is it not?
|
|
|
|
Meno: Yes, Socrates, but I don't see how he will do it.
|
|
|
|
Socrates: Neither does he. But I do. Watch! (turning to
|
|
the boy) Now I am going to tell you something you don't know,
|
|
so Meno will listen very closely to make sure he agrees that I can
|
|
tell you. You know multiplication, boy?
|
|
|
|
Boy: I thought I had demonstrated that, Socrates?
|
|
|
|
Socrates: So you have, my boy, has he not Meno?
|
|
|
|
Meno: Yes, Socrates, I recall he did the other day.
|
|
|
|
Socrates: And you know the way to undo multiplication?
|
|
|
|
Boy: It is called division, but I do not know it as well as
|
|
multiplication, since we have not studied it as long.
|
|
|
|
Socrates: Well, I will not ask you to do much division, but
|
|
rather I will ask you only whether certain answers may be
|
|
called odd or even, and the like. Does that suit you?
|
|
|
|
Boy: It suits me well, Socrates.
|
|
|
|
Socrates: Then you know what odd and even are, boy?
|
|
|
|
Boy: Yes, shall I tell you?
|
|
|
|
Socrates: Please do. I would love to hear what they teach.
|
|
|
|
Boy: (the boy recites) A number can only be odd or even if it
|
|
is a whole number, that is has no parts but only wholes of what
|
|
it measures. Even numbers are special in that they have only
|
|
whole twos in them, with no ones left over, while odd numbers
|
|
always have a one left over when all the twos are taken out.
|
|
|
|
Socrates: An interesting, and somewhat effective definition.
|
|
Do you agree, Meno.
|
|
|
|
Meno: Yes, Socrates. Please continue.
|
|
|
|
Socrates: Now boy, what do you get when you divide these
|
|
odd and even numbers by other odd and even numbers.
|
|
|
|
Boy: Sometimes you get whole numbers, especially when you
|
|
divide an even number by an even number, but odd numbers
|
|
sometimes give whole numbers, both odd and even, and sometimes
|
|
they give numbers which are not whole numbers, but have parts.
|
|
|
|
Socrates: Very good, and have your teachers ever called
|
|
these numbers ratios?
|
|
|
|
Boy: Sometimes, Socrates, but usually only with simple numbers
|
|
which make one-half, one-third, two-thirds and the like.
|
|
|
|
Socrates: Yes, that is usually what people mean by ratios.
|
|
The learned people call numbers made from the ratios, rational.
|
|
Does the name rational number suit you to call a number which can
|
|
be expressed as the ratio of two whole numbers, whether they be
|
|
odd or even whole number?
|
|
|
|
Boy: You want me to call the numbers made from ratios of
|
|
whole numbers something called rational? A ratio makes a
|
|
rational number?
|
|
|
|
Socrates: Yes boy, can you do that?
|
|
|
|
Boy: Certainly, Socrates.
|
|
|
|
Socrates: Do you agree with the way I told him this, Meno?
|
|
Does it violate our agreement?
|
|
|
|
Meno: You added -nal to the word ratio, just as we add -nal
|
|
to the French work "jour" to create the word journal which mean
|
|
something that contains words of the "jour" or of today. So we
|
|
now have a word which means a number made from a ratio. This is
|
|
more than acceptable to me, Socrates. A sort of lesson in
|
|
linguistics, perhaps, but certainly not in mathematics. No, I do
|
|
not see that you have told him how to solve anything about the
|
|
square root of two, but thank you for asking. I give you your
|
|
journalistic license to do so.
|
|
|
|
Socrates: Good. Now boy, I need your attention. Please get
|
|
up and stretch, if it will help you stay and thing for awhile.
|
|
|
|
Boy: (stretches only a little) I am fine, Socrates.
|
|
|
|
Socrates: Now think carefully, boy, what kind of ratios can
|
|
we make from even numbers and odd numbers?
|
|
|
|
Boy: We could make even numbers divided by odd numbers, and
|
|
odd numbers divided by even numbers.
|
|
|
|
Socrates: Yes, we could. Could we make any other kind?
|
|
|
|
Boy: Well . . . we could make even numbers divided by even
|
|
numbers, or odd numbers divided by odd.
|
|
|
|
Socrates: Very good. Any other kind?
|
|
|
|
Boy: I'm not sure, I can't think of any, but I might have to
|
|
think a while to be sure.
|
|
|
|
Socrates: (to Meno) Are you still satisfied.
|
|
|
|
Meno: Yes, Socrates. He knows even and odd numbers,
|
|
and ratios; as do all the school children his age.
|
|
|
|
Socrates: Very well, boy. You have named four kinds of
|
|
ratios: Even over odd, odd over even, even over even, odd over
|
|
odd, and all the ratios make numbers we call rational numbers.
|
|
|
|
Boy: That's what it looks like, Socrates.
|
|
|
|
Socrates: Meno, have you anything to contribute here?
|
|
|
|
Meno: No, Socrates, I am fine.
|
|
|
|
Socrates: Very well. Now, boy, we are off in search of more
|
|
about the square root of two. We have divided the rational numbers
|
|
into four groups, odd/even, even/odd, even/even, odd/odd?
|
|
|
|
Boy: Yes.
|
|
|
|
Socrates: And if we find another group we can include them.
|
|
Now, we want to find which one of these groups, if any, contains
|
|
the number you found the other day, the one which squared is two.
|
|
|
|
Would that be fun to try?
|
|
|
|
Boy: Yes, Socrates, and also educational.
|
|
|
|
Socrates: I think we can narrow these four groups down to
|
|
three, and thus make the search easier. Would you like that?
|
|
|
|
Boy: Certainly, Socrates.
|
|
|
|
Socrates: Let's take even over even ratios. What are they?
|
|
|
|
Boy: We know that both parts of the ratio have two in them.
|
|
|
|
Socrates: Excellent. See, Meno, how well he has learned his
|
|
lessons in school. His teacher must be proud, for I have taught
|
|
him nothing of this, have I?
|
|
|
|
Meno: No, I have not seen you teach it to him,
|
|
therefore he must have been exposed to it elsewhere.
|
|
|
|
Socrates: (back to the boy) And what have you learned about
|
|
ratios of even numbers, boy?
|
|
|
|
Boy: That both parts can be divided by two, to get the twos
|
|
out, over and over, until one part becomes odd.
|
|
|
|
Socrates: Very good. Do all school children know that, Meno?
|
|
|
|
Meno: All the ones who stay away in class. (he stretches)
|
|
|
|
Socrates: So, boy, we can change the parts of the ratios,
|
|
without changing the real meaning of the ratio itself?
|
|
|
|
Boy: Yes, Socrates. I will demonstrate, as we do in class.
|
|
Suppose I use 16 and 8, as we did the other day. If I make a
|
|
ratio of 16 divided by 8, I can divide both the 16 and the 8 by
|
|
two and get 8 divided by 4. We can see that 8 divided by four is
|
|
the same as 16 divided by 8, each one is twice the other, as it
|
|
should be. We can then divide by two again and get 4 over 2, and
|
|
again to get 2 over 1. We can't do it again, so we say that this
|
|
fraction has been reduced as far as it will go, and everything
|
|
that is true of the other ways of expressing it is true of this.
|
|
|
|
Socrates: Your demonstration is effective. Can you divide
|
|
by other numbers than two?
|
|
|
|
Boy: Yes, Socrates. We can divide by any number which goes
|
|
as wholes into the parts which make up the ratio. We could have
|
|
started by dividing by 8 before, but I divided by three times,
|
|
each time by two, to show you the process, though now I feel
|
|
ashamed because I realize you are both masters of this,
|
|
and that I spoke to you in too simple a manner.
|
|
|
|
Socrates: Better to speak too simply, than in a manner in
|
|
which part or all of your audience gets lost, like the Sophists.
|
|
|
|
Boy: I agree, but please stop me if I get too simple.
|
|
|
|
Socrates: I am sure we can survive a simple explanation.
|
|
(nudges Meno, who has been gazing elsewhere) But back to your
|
|
simple proof: we know that a ratio of two even number can be
|
|
divided until reduced until one or both its parts are odd?
|
|
|
|
Boy: Yes, Socrates. Then it is a proper ratio.
|
|
|
|
Socrates: So we can eliminate one of our four groups, the
|
|
one where even was divided by even, and now we have odd/odd,
|
|
odd/even and even/odd?
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: Let's try odd over even next, shall we?
|
|
|
|
Boy: Fine.
|
|
|
|
Socrates: What happens when you multiply an even number by
|
|
an even number, what kind of number do you get, even or odd?
|
|
|
|
Boy: Even, of course. An even multiple of any whole number
|
|
gives another even number.
|
|
|
|
Socrates: Wonderful, you have answered two question, but we
|
|
need only one at the moment. We shall save the other. So, with
|
|
odd over even, if we multiply any of these times themselves, we
|
|
well get odd times odd over even times even, and therefore odd
|
|
over even, since odd times odd is odd and even of even is even.
|
|
|
|
Boy: Yes. A ratio of odd over even, when multiplied times
|
|
itself, yields odd over even.
|
|
|
|
Socrates: And can our square root of two be in that group?
|
|
|
|
Boy: I don't know, Socrates. Have I failed?
|
|
|
|
Socrates: Oh, you know, you just don't know that you know.
|
|
|
|
Try this: after we multiply our number times itself,
|
|
which the learned call "squaring" the number which is the root,
|
|
we need to get a ratio in which the first or top number is twice
|
|
as large as the second or bottom number. Is this much correct?
|
|
|
|
Boy: A ratio which when "squared" as you called it, yields
|
|
an area of two, must then yield one part which is two times the
|
|
other part. That is the definition of a ratio of two to one.
|
|
|
|
Socrates: So you agree that this is correct?
|
|
|
|
Boy: Certainly.
|
|
|
|
Socrates: Now if a number is to be twice a great as another,
|
|
it must be two times that number?
|
|
|
|
Boy: Certainly.
|
|
|
|
Socrates: And if a number is two times any whole number,
|
|
it must then be an even number, must it not?
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: So, in our ratio we want to square to get two,
|
|
the top number cannot be odd, can it?
|
|
|
|
Boy: No, Socrates. Therefore, the group of odd over even
|
|
rational numbers cannot have the square root of two in it!
|
|
Nor can the group ratios of odd numbers over odd numbers.
|
|
|
|
Socrates: Wonderful. We have just eliminated three of the
|
|
four groups of rational numbers, first we eliminated the
|
|
group of even over even numbers, then the ones with odd numbers
|
|
divided by other numbers. However, these were the easier part,
|
|
and we are now most of the way up the mountain, so we must rest
|
|
and prepare to try even harder to conquer the rest, where the
|
|
altitude is highest, and the terrain is rockiest. So let us sit
|
|
and rest a minute, and look over what we have done, if you will.
|
|
|
|
Boy: Certainly, Socrates, though I am much invigorated by
|
|
the solution of two parts of the puzzle with one thought.
|
|
It was truly wonderful to see such simple effectiveness.
|
|
Are all great thoughts as simple as these, once you see them clearly?
|
|
|
|
Socrates: What do you say, Meno? Do thoughts get simpler as
|
|
they get greater?
|
|
|
|
Meno: Well, it would appear that they do, for as the master
|
|
of a great house, I can just order something be done, and it is;
|
|
but if I were a master in a lesser house, I would have to watch
|
|
over it much more closely to insure it got done. The bigger the
|
|
decisions I have to make, the more help and advice I get in the
|
|
making of them, so I would have to agree.
|
|
|
|
Socrates: Glad to see that you are still agreeable, Meno,
|
|
though I think there are some slight differences in the way each
|
|
of us view the simplicity of great thought. Shall we go on?
|
|
|
|
Meno: Yes, quite.
|
|
|
|
Boy: Yes, Socrates. I am ready for the last group, the
|
|
ratios of even numbers divided by the odd, though, I cannot yet
|
|
see how we will figure these out, yet, somehow I have confidence
|
|
that the walls of these numbers shall tumble before us, as did
|
|
the three groups before them.
|
|
|
|
Socrates: Let us review the three earlier groups, to prepare
|
|
us for the fourth, and to make sure that we have not already
|
|
broken the rules and therefore forfeited our wager. The four
|
|
groups were even over even ratios, which we decided could be
|
|
reduced in various manners to the other groups by dividing until
|
|
one number of the ratio was no longer even; then we eliminated
|
|
the two other groups which had odd numbers divided by either odd
|
|
or even numbers, because the first or top number had to be twice
|
|
the second or bottom number, and therefore could not be odd;
|
|
this left the last group we are now to greet, even divided by odd.
|
|
|
|
Boy: Wonderfully put, Socrates. It is amazing how neatly
|
|
you put an hour of thinking into a minute. Perhaps we can,
|
|
indeed, put ten years of thinking into this one day. Please
|
|
continue in this manner, if you know how it can be done.
|
|
|
|
Socrates: Would you have me continue, Meno? You know what
|
|
shall have to happen if we solve this next group and do not
|
|
find the square root of two in it.
|
|
|
|
Meno: Socrates, you are my friend, and my teacher, and a
|
|
good companion. I will not shirk my duty to you or to this fine
|
|
boy, who appears to be growing beyond my head, even as we speak.
|
|
However, I still do not see that his head has reached the clouds
|
|
wherein lie the minds of the Pythagoreans.
|
|
|
|
Socrates: Very well, on then, to even over odd. If we multiply
|
|
these numbers times themselves, what do we get, boy?
|
|
|
|
Boy: We will get a ratio of even over odd, Socrates.
|
|
|
|
Socrates: And could an even number be double an odd number?
|
|
|
|
Boy: Yes, Socrates.
|
|
|
|
Socrates: So, indeed, this could be where we find a number
|
|
such that when multiplied times itself yields an area of two?
|
|
|
|
Boy: Yes, Socrates. It could very well be in this group.
|
|
|
|
Socrates: So, the first, or top number, is the result of an
|
|
even number times itself?
|
|
|
|
Boy: Yes.
|
|
|
|
Socrates: And the second, or bottom number, is the result of
|
|
an odd number times itself?
|
|
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Boy: Yes.
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Socrates: And an even number is two times one whole number?
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Boy: Of course.
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Socrates: So if we use this even number twice in multiplication,
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as we have on top, we have two twos times two whole numbers?
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Boy: Yes, Socrates.
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Socrates: (nudges Meno) and therefore the top number is four
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times some whole number times that whole number again?
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Boy: Yes, Socrates.
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Socrates: And this number on top has to be twice the number
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on the bottom, if the even over odd number we began with is to
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give us two when multiplied by itself, or squared, as we call it?
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Boy: Yes, Socrates.
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Socrates: And if the top number is four times some whole number,
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then a number half as large would have to be two times that same whole number?
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Boy: Of course, Socrates.
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Socrates: So the number on the bottom is two times that whole number,
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whatever it is?
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Boy: Yes, Socrates.
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Socrates: (standing) And if it is two times a whole number,
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then it must be an even number, must it not?
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Boy: Yes.
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Socrates: Then is cannot be a member of the group which has
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an odd number on the bottom, can it?
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Boy: No, Socrates.
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Socrates: So can it be a member of the ratios created by an
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even number divided by an odd number and then used as a root
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to create a square?
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Boy: No, Socrates. And that must mean it can't be a member
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of the last group, doesn't it?
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Socrates: Yes, my boy, although I don't see how we can
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continue calling you boy, since you have now won your freedom,
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and are far richer than I will ever be.
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Boy: Are you sure we have proved this properly? Let me go
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over it again, so I can see it in my head.
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Socrates: Yes, my boy, er, ah, sir.
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Boy: We want to see if this square root of two we discovered
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the other day is a member of the rational numbers?
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Socrates: Yes.
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Boy: So we define the rational numbers as numbers made from
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the division into ratios of whole numbers, whether those whole
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numbers are even or odd.
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Socrates: Yes.
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Boy: We get four groups, even over even, which we don't use,
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odd over even, odd over odd, and even over odd.
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Socrates: Continue.
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Boy: We know the first number in the squared ratio cannot be odd
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because it must be twice the value of the second number,
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and therefore is must be an even number, two times a whole number.
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Therefore it cannot be a member of either of the next groups,
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because they both have whole numbers over odd numbers.
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Socrates: Wonderful!
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Boy: So we are left with one group, the evens over odds.
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Socrates: Yes.
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Boy: When we square an even over odd ratio, the first number
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becomes even times even, which is two times two times some other
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whole number, which means it is four times the whole number,
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and this number must be double the second number, which is odd,
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as it was made of odd times odd. But the top number cannot be double
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some bottom odd number because the top number is four times some
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whole number, and the bottom number is odd--but a number which is
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four times another whole number, cannot be odd when cut in half,
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so an even number times an even number can never be double what
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you would get from any odd number times another odd number. . .
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therefore none of these rational numbers, when multiplied times
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themselves, could possibly yield a ratio in which the top number
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was twice the bottom number. Amazing. We have proved that the
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square root of two is not a rational number. Fantastic!
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(he continues to wander up and down the stage, reciting various
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portions of the proof to himself, looking up, then down, then all
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around. He comes to Meno)
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Boy: Do you see? It's so simple, so clear. This is really wonderful!
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This is fantastic!
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Socrates: (lays an arm on Meno's arm) Tell him how happy
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you are for his new found thoughts, Meno, for you can easily tell
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he is not thinking at all of his newly won freedom and wealth.
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Meno: I quite agree with you, son, the clarity of your
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reasoning is truly astounding. I will leave you here with
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Socrates, as I go to prepare my household. I trust you will
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both be happy for the rest of the day without my assistance.
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[The party, the presentation of 10 years salary to the newly
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freed young man, is another story, as is the original story
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of the drawing in the sant the square with an area of two.]
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End of Project Gutenberg's Etext of the Second Story of Meno
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