STRANGER: I believe that I can see how we shall soonest arrive at the

answer to this question.

THEAETETUS: How?

STRANGER: If we can discover a line which divides ignorance into two

halves. For a division of ignorance into two parts will certainly

imply that the art of instruction is also twofold, answering to the two

divisions of ignorance.

THEAETETUS: Well, and do you see what you are looking for?

STRANGER: I do seem to myself to see one very large and bad sort of

ignorance which is quite separate, and may be weighed in the scale

against all other sorts of ignorance put together.

THEAETETUS: What is it?

STRANGER: When a person supposes that he knows, and does not know; this

appears to be the great source of all the errors of the intellect.

THEAETETUS: True.

STRANGER: And this, if I am not mistaken, is the kind of ignorance which

specially earns the title of stupidity.

Sophist