Dialogues

knows and perceives, and of which he has the impression coinciding with sense, is something else which he knows and perceives, and of which he has the impression coinciding with sense;⁠—this last case, if possible, is still more inconceivable than the others; nor (4) can he think that something which he knows and perceives, and of which he has the memorial coinciding with sense, is something else which he knows; nor so long as these agree, can he think that a thing which he knows and perceives is another thing which he perceives; or that a thing which he does not know and does not perceive, is the same as another thing which he does not know and does not perceive;⁠—nor again, can he suppose that a thing which he does not know and does not perceive is the same as another thing which he does not know; or that a thing which he does not know and does not perceive is another thing which he does not perceive:⁠—All these utterly and absolutely exclude the possibility of false opinion. The only cases, if any, which remain, are the following. Theaetetus What are they? If you tell me, I may perhaps understand you better; but at present I am unable to follow you. Socrates A person may think that some things which he knows, or which he perceives and does not know, are some other things which he knows and perceives; or that some things which he knows and perceives, are other things which he knows and perceives. Theaetetus I understand you less than ever now. Socrates Hear me once more, then:⁠—I, knowing Theodorus, and remembering in my own mind what sort of person he is, and also what sort of person Theaetetus is, at one time see them, and at another time do not see them, and sometimes I touch them, and at another time not, or at one time I may hear them or perceive them in some other way, and at another time not perceive them, but still I remember them, and know them in my own mind. Theaetetus Very true. Socrates Then, first of all, I want you to understand that a man may or may not perceive sensibly that which he knows. Theaetetus True. Socrates And that which he does not know will sometimes not be perceived by him and sometimes will be perceived and only perceived? Theaetetus That is also true. Socrates See whether you can follow me better now: Socrates can recognize Theodorus and Theaetetus, but he sees neither of them, nor does he perceive them in any other way; he cannot then by any possibility imagine in his own mind that Theaetetus is Theodorus. Am I not right? Theaetetus You are quite right. Socrates Then that was the first case of which I spoke. Theaetetus Yes. Socrates The second case was, that I, knowing one of you and not knowing the other, and perceiving neither, can never think him whom I know to be him whom I do not know. Theaetetus True. Socrates In the third case, not knowing and not perceiving either of you, I cannot think that one of you whom I do not know is the other whom I do not know. I need not again go over the catalogue of excluded cases, in which I cannot form a false opinion about you and Theodorus, either when I know both or when I am in ignorance of both, or when I know one and not the other. And the same of perceiving: do you understand me? Theaetetus I do. Socrates The only possibility of erroneous opinion is, when knowing you and Theodorus, and having on the waxen block the impression of both of you given as by a seal, but seeing you imperfectly and at a distance, I try to assign the right impression of memory to the right visual impression, and to fit this into its own print: if I succeed, recognition will take place; but if I fail and transpose them, putting the foot into the wrong shoe⁠—that is to say, putting the vision of either of you on to the wrong impression, or if my mind, like the sight in a mirror, which is transferred from right to left, err by reason of some similar affection, then “heterodoxy” and false opinion ensues. Theaetetus Yes, Socrates, you have described the nature of opinion with wonderful exactness. Socrates Or again, when I know both of you, and perceive as well as know one of you, but not the other, and my knowledge of him does not accord with perception⁠—that was the case put by me just now which you did not understand. Theaetetus No, I did not. Socrates I meant to say, that when a person knows and perceives one of you, his knowledge coincides with his perception, he will never think him to be some other person, whom he knows and perceives, and the knowledge of whom coincides with his perception⁠—for that also was a case supposed. Theaetetus True. Socrates But there was an omission of the further case, in which, as we now say, false opinion may arise, when knowing both, and seeing, or having some other sensible perception of both, I fail in holding the seal over against the corresponding sensation; like a bad archer, I miss and fall wide of the mark⁠—and this is called falsehood. Theaetetus Yes; it is rightly so called. Socrates When, therefore, perception is present to one of the seals or impressions but not to the other, and the mind fits the seal of the absent perception on the one which is present, in any case of this sort the mind is deceived; in a word, if our view is sound, there can be no error or deception about things which a man does not know and has never perceived, but only in things which are known and perceived; in these alone opinion turns and twists about, and becomes alternately true and false;⁠—true when the seals and impressions of sense meet straight and opposite⁠—false when they go awry and crooked. Theaetetus And is not that, Socrates, nobly