Stranger: Who must be you, and can be nobody else?
Theaetetus: Unquestionably.
Stranger: And it would be no sentence at all if there were no subject, for, as we proved, a sentence which has no subject is impossible.
Theaetetus: Quite true.
Stranger: When other, then, is asserted of you as the same, and not-being as being, such a combination of nouns and verbs is really and truly false discourse.
Theaetetus: Most true.
Stranger: And therefore thought, opinion, and imagination are now proved to exist in our minds both as true and false.
Theaetetus: How so?
Stranger: You will know better if you first gain a knowledge of what they are, and in what they severally differ from one another.
Theaetetus: Give me the knowledge which you would wish me to gain.
Stranger: Are not thought and speech the same, with this exception, that what is called thought is the unuttered conversation of the soul with herself?
Theaetetus: Quite true.
Stranger: But the stream of thought which flows through the lips and is audible is called speech?
Theaetetus: True.
Stranger: And we know that there exists in speech …
Theaetetus: What exists?
Stranger: Affirmation.
Theaetetus: Yes, we know it.
Stranger: When the affirmation or denial takes Place in silence and in the mind only, have you any other name by which to call it but opinion?
Theaetetus: There can be no other name.
Stranger: And when opinion is presented, not simply, but in some form of sense, would you not call it imagination?
Theaetetus: Certainly.
Stranger: And seeing that language is true and false, and that thought is the conversation of the soul with herself, and opinion is the end of thinking, and imagination or fantasy is the union of sense and opinion, the inference is that some of them, since they are akin to language, should have an element of falsehood as well as of truth?
Theaetetus: Certainly.
Stranger: Do you perceive, then, that false opinion and speech have been discovered sooner than we expected?—For just now we seemed to be undertaking a task which would never be accomplished.