One of the classic metaphors for the teacher is to be found in this short section from Plato's Theaetetus (148e-151d, translated by F. N. Cornford). Socrates is questioning the young man Theaetetus about what constitutes "knowledge." Theaetetus is not certain he can provide sensible answers. The dialogue is set in the year 299 B.C., it was probably written about 257 B.C.
THEAETETUS: But I assure you Socrates, I have often set myself to study (the problem of defining knowledge) when I heard reports of the questions you ask. But I cannot persuade myself that I can give any satisfactory solution or that anyone has ever stated in my hearing the sort of answer you require. And yet I cannot get the question out of my mind.
SOCRATES: My dear Theaetetus, that is because your mind is not empty or barren. You are suffering the pains of travail.
THEAETETUS: I don't know about that, Socrates. I am only telling you how I feel.
SOCRATES: How absurd of you, never to have heard that I am the son of a midwife, a fine buxom woman called Phaenarete!
THEAETETUS: I have heard that.
SOCRATES: Have you also been told that I practice the same art?
THEAETETUS: No, never.
SOCRATES: It is true, though, only don't give away my secret. It is not known that I possess this skill; so the ignorant world describes me in other terms as an eccentric person who reduces people to hopeless perplexity. Have you been told that too?
THEAETETUS: I have.
SOCRATES: Shall I tell you the reason?
THEAETETUS: Please do.
SOCRATES: Consider, then, how it is with all midwives; that will help you to understand what I mean. I dare say you know that they never attend other women in childbirth so long as they themselves can conceive and bear children, but only when they are too old for that.
THEAETETUS: Of course.
SOCRATES: They say that is because Artemis, the patroness of childbirth, is herself childless, and so, while she did not allow barren women to be midwives, because it is beyond the power of human nature to achieve skill without any experience, she assigned the privilege to women who were past childbearing, out of respect to their likeness to herself.
THEAETETUS: That sounds likely.
SOCRATES: And it is more likely, is it not, that no one can tell so well as a midwife whether women are pregnant or not?
THEAETETUS: Assuredly.
SOCRATES: Moreover, with the drugs and incantations they administer, midwifes can either bring on the pains of travail or allay them at their will, make a difficult labor easy and at an early stage cause miscarriage if they so decide.
THEAETETUS: True.
SOCRATES: Have you also observed that they are the cleverest matchmakers, having an unerring skill in selecting a pair whose marriage will produce the best children?
THEAETETUS: I was not aware of that.
SOCRATES: Well, you may be sure they pride themselves on that more than on cutting the umbilical cord. Consider the knowledge of the sort of plant of seed that should be sown in any given soul. Does not that go together with skill in tending and harvesting the fruits of the earth? They are not two different arts?
THEAETETUS: No, the same.
SOCRATES: And so with a woman; skill in the sowing is not be separated from skill in the harvesting?
THEAETETUS: Probably not.
SOCRATES: No. Only because there is that wrong and ignorant way of bringing together man and woman which they call pandering, midwives, out of self-respect, are shy even of matchmaking, for fear of falling under the accusation of pandering. Yet the genuine midwife is the only successful matchmaker.
THEAETETUS: That is clear.
SOCRATES: All this, then lies within the midwife's province, but her performance falls short of mine. It is not the way of women sometimes to bring forth real children, sometimes mere phantoms, such that it is hard to tell the one from the other. If it were so, the highest and noblest task of the midwife would be to discern the real from the unreal, would it not?
THEAETETUS: I agree.
SOCRATES: My art of midwifery is in general like theirs; the only difference is that my patients are men, not women, and my concern is not with the body but with the soul that is in travail of birth. And the highest point of my art is the power to prove by every test whether the offspring of a young man's thought is a false phantom, or instinct with life and truth. I am so far like the midwife that I cannot myself give birth to wisdom, and the common reproach is true, that, though I question others, I can myself bring nothing to light because there is no wisdom in me.
The reason is this. Heaven constrains me to serve as a midwife, but has debarred me from giving birth. So of myself I have no sort of wisdom, nor has any discovery ever been born to me as the child unintelligent, but, as we go further with our discussions, all who are favored by heaven make progress at a rate that seems surprising to others as well as to themselves, although it is clear that they have never learned anything from me. The many admirable truths they bring to birth have been discovered by themselves from within. But the delivery is heaven's work and mine.
The proof of this is that many who have not been conscious of my assistance but have made light of me, thinking it was all their own doing, have left me sooner than they should, whether under others' influence or of their own motion, and thenceforward suffered miscarriage of their thoughts through falling into bad company, and they have lost the children of whom I had delivered them by bringing them up badly, caring more for false phantoms than for the true. And so at last their lack of understanding has become apparent to themselves and to everyone else. Such a one was Aristides, son of Lysimachus, and there have been many more. When they come back and beg for a renewal of our intercourse with extravagant protestations, sometimes the divine warning that comes to me forbids it; with others it is permitted, and these begin again to make progress.
In yet another way those who seek my company have the same experience as a woman with child; they suffer the pains of labor and, by night and day, are full of distress far greater than a woman's, and my art has power to bring on those pangs or to allay them. So it fares with these, but there are some, Theaetetus, whose minds, as I judge, have never conceived at all. I see that they have no need of me and with all good will I seek a match for them. Without boasting unduly I can guess pretty well whose society will profit them. I have arranged many of these matches with Prodicus, and with other men of inspired sagacity.
And now for the upshot of this long discourse of mine. I suspect that, as you yourself believe, your mind is in labor with some thought it has conceived. Accept then, the ministration of a midwife's son who himself practices his mother's art, and do the best you can to answer the questions I ask. Perhaps when I examine your statements I may judge one or another of them to be an unreal phantom.
If I then take the abortion from you and cast it away, do not be savage with me like a woman robbed of her first child. People have often felt like that toward me and been positively ready to bite me for taking away some foolish notion they have conceived. They do not see that I am doing them a kindness. They have not learned that no divinity is ever ill-disposed toward man, nor is such action on my part due to unkindness; it is only that I am not permitted to acquiesce in falsehood and suppress the truth.
So, Theaetetus, start again and try to explain what knowledge is. Never say it is beyond your power; it will not be so, if heaven wills and you take courage.