SOCRATES: I am not only out of heart, but in positive despair; for I do not know what to answer if any one were to ask me:—O Socrates, have you indeed discovered that false opinion arises neither in the comparison of perceptions with one another nor yet in thought, but in union of thought and perception? Yes, I shall say, with the complacence of one who thinks that he has made a noble discovery.
THEAETETUS: I see no reason why we should be ashamed of our demonstration, Socrates.
SOCRATES: He will say: You mean to argue that the man whom we only think of and do not see, cannot be confused with the horse which we do not see or touch, but only think of and do not perceive? That I believe to be my meaning, I shall reply.
THEAETETUS: Quite right.
SOCRATES: Well, then, he will say, according to that argument, the number eleven, which is only thought, can never be mistaken for twelve, which is only thought: How would you answer him?
THEAETETUS: I should say that a mistake may very likely arise between the eleven or twelve which are seen or handled, but that no similar mistake can arise between the eleven and twelve which are in the mind.
SOCRATES: Well, but do you think that no one ever put before his own mind five and seven,—I do not mean five or seven men or horses, but five or seven in the abstract, which, as we say, are recorded on the waxen block, and in which false opinion is held to be impossible; did no man ever ask himself how many these numbers make when added together, and answer that they are eleven, while another thinks that they are twelve, or would all agree in thinking and saying that they are twelve?
THEAETETUS: Certainly not; many would think that they are eleven, and in the higher numbers the chance of error is greater still; for I assume you to be speaking of numbers in general.
SOCRATES: Exactly; and I want you to consider whether this does not imply that the twelve in the waxen block are supposed to be eleven?
THEAETETUS: Yes, that seems to be the case.