Plato writes:

Socr. I have heard it said, then, that at Naucratis in Egypt there lived one of the old gods of that country, the one whose sacred bird is called the ibis; and the name of the divinity was Theuth. It was he who first invented numbers and arithmetic, geometry and astronomy, dicing, too, and the game of draughts and, most particularly and especially, writing. Now the King of all Egypt at that time was Thamus who lived in the great city of the upper region which the Greeks call the Egyptian Thebes; the god himself they call Ammon. Theuth came to him and exhibited his arts and declared that they ought to be imparted to the other Egyptians. And Thamus questioned him about the usefulness of each one; and as Theuth enumerated, the King blamed or praised what he thought were the good or bad points in the explanation. . . . When it came to writing, Theuth said, "This discipline, my King, will make the Egyptians wiser and will improve their memories: my invention is a recipe for both memory and wisdom." But the King said, "Theuth, my master of arts, to one man it is given to create the elements of an art, to another to judge the extent of harm and usefulness it will have for those who are going to employ it. And now, since you are father of written letters, your paternal goodwill has led you to pronounce the very opposite of what is their real power. The fact is that this invention will produce forgetfulness in the souls of those who have learned it. They will not need to exercise their memories, being able to rely on what is written, calling things to mind no longer from within themselves by their own unaided powers, but under the stimulus of external marks that are alien to themselves. So it's not a recipe for memory, but for reminding, that you have discovered. And as for wisdom, you're equipping your pupils with only a semblance of it, not with truth. Thanks to you and your invention, your pupils will be widely read without benefit of a teacher's instruction; in consequence, they'll entertain the delusion that they have wide knowledge, while they are, in fact, for the most part incapable of real judgment. They will also be difficult to get on with since they will have become wise merely in their own conceit, not genuinely so." . . .

Then any man who imagines that he has bequeathed an art to posterity because he put his views in writing, and also anyone who inherits such an "art" in the belief that any subject will be clear or certain because it is couched in writing such men will be utterly simple-minded. They must be really ignorant of Zeus Ammon's method of delivering prophetic truth if they believe that words put in writing are something more than what they are in fact: a reminder to a man, already conversant with the subject of the material with which the writing is concerned.

Phaedr. Quite right.

Socr. Writing, you know, Phaedrus, has this strange quality about it, which makes it really like painting: the painter's products stand before us quite as though they were alive; but if you question them, they maintain a solemn silence. So, too, with written words: you might think they spoke as though they made sense, but if you ask them anything about what they are saying, if you wish an explanation, they go on telling you the same thing, over and over forever. Once a thing is put in writing, it rolls about all over the place, falling into the hands of those who have no concern with it just as easily as under the notice of those who comprehend; it has no notion of whom to address or whom to avoid. And when it is ill-treated or abused as illegitimate, it always needs its father to help it, being quite unable to protect or help itself.

Phaedr. You're quite right about that, too.

Socr. Well then, are we able to imagine another sort of discourse a legitimate brother of our bastard? How does it originate? How far is it better and more powerful in nature?

Phaedr. What sort of discourse? What do you mean about its origin?

Socr. A discourse which is inscribed with genuine knowledge in the soul of the learner; a discourse that can defend itself and knows to whom it should speak and before whom to remain silent.

Phaedr. Do you mean the living, animate discourse of a man who really knows? Would it be fair to call the written discourse only a kind of ghost of it?

Socr. Precisely. Now tell me this: take a sensible farmer who has seed he is anxious to tend properly and wants it to yield him a good full crop: would he seriously plant it during the summer, and in forcing-areas at that, and then take pleasure in the spectacle of a fine crop on the eighth day? If he ever did such a thing, wouldn't it be just for fun or to meet the needs of a special festival? But with seed that he was really serious about, wouldn't he make full use of scientific husbandry and plant it in suitable soil and be perfectly satisfied if it came to maturity in the eighth month?

Phaedr. As you know, Socrates, the latter would be a serious act, the former quite different, and motivated as you say.

Socr. Shall we suppose that a man who has real knowledge of justice and beauty and goodness will have less intelligence about his own seeds than a farmer does?

Phaedr. By no means.

Socr. Then he will not, when he's in earnest, resort to a written form and inscribe his seeds in water, and in inky water at that; he will not sow them with a pen, using words which are unable either to argue in their own defense when attacked or to fulfill the role of a teacher in presenting the truth. . . . In this regard, far more noble and splendid is the serious pursuit of the dialectician, who finds a congenial soul and then proceeds with true knowledge to plant and sow in it words which are able to help themselves and help him who planted them; words which will not be unproductive, for they can transmit their seed to other natures and cause the growth of fresh words in them, providing an eternal existence for their seed; words which bring their possessor to the highest degree of happiness possible for a human being to attain.

(Phaedrus 67-71)