"Once more then, just as a while ago we imagined a sort of waxen block in our minds, so now let us suppose that every mind contains a kind of aviary stocked with birds of every sort, some in flocks apart from the rest, some in small groups, and some solitary, flying in any direction among them all."
— Plato (427 BC - 347 BC)
THEAETETUS: Be it so. What follows?
SOCRATES: When we are babies we must suppose this receptacle empty, and take the birds to stand for pieces of knowledge. Whenever a person acquires any piece of knowledge and shuts it up in his enclosure, we must say he has learned or discovered the thing of which this is the knowledge, and that is what 'knowing' means.
THEAETETUS: Be it so.
SOCRATES: Now think of him hunting once more for any piece of knowledge that he wants, catching and holding it, and letting it go again. In what terms are we to describe that--the same that we used of the original process of acquisition, or different ones? An illustration may help you to see what I mean. There is a science you call 'arithmetic.'
SOCRATES: Conceive that, then, as a chase after pieces of knowledge about all the numbers, odd or even.
THEAETETUS: I will.
SOCRATES: That, I take it, is the science in virtue of which a man has in his control pieces of knowledge about numbers and can hand them over to someone else.
SOCRATES: And when he hands them over, we call it 'teaching,' and when the other takes them from him, that is 'learning,' and when he has them in the sense of possessing them in that aviary of his, that is 'knowing.'
(197e-198b, p. 904)