"But _you_ also" (retorts Sokrates upon the couple), "do not you also know some things, not know others?--By no means.--What! do you know nothing?--Far from it.--Then you know all things?--Certainly we do,--and you too: if you know one thing, you know all things.--What! do you know the art of the carpenter, the currier, the cobbler--the number of stars in the heaven, and of grains of sand in the desert, &c.?--Yes: we know all these things." [Side-note: Obstinacy shown by the two Sophists in their replies--determination not to contradict themselves.] The two Sophists maintain their consistency by making reply in the affirmative to each of these successive questions: though Ktesippus pushes them hard by enquiries as to a string of mean and diverse specialties.[50] This is one of the purposes of the dialogue: to represent the two Sophists as willing to answer any thing, however obviously wrong and false, for the purpose of avoiding defeat in the dispute--as using their best efforts to preserve themselves in the position of questioners, and to evade the position of respondents--and as exacting a categorical answer--Yes or No--to every question which they put without any qualifying words, and without any assurance that the meaning of the question was understood.[51] [Footnote 50: Plato, Euthydêm. pp. 293-294.] [Footnote 51: Plato, Euthydêm. pp. 295-296.] The base of these fallacious inferences is, That respecting the same subject, you cannot both affirm and deny the same predicate: you cannot say, A is knowing--A is not knowing ([Greek: e)pistê/môn]). This is a fallacy more than verbal: it is recognised by Aristotle (and by all subsequent logicians) under the name--_à dicto secundum quid, ad dictum simpliciter_. It is very certain that this fallacy is often inadvertently committed by very competent reasoners, including both Plato and Aristotle. [Side-note: Farther verbal equivocations.] Again--Sophroniskus was my father--Chæredemus was the father of Patrokles.--Then Sophroniskus was different from a father: therefore he was not a father. You are different from a stone, therefore you are not a stone: you are different from gold, therefore you are not gold. By parity of reasoning, Sophroniskus is different from a father--therefore he is not a father. Accordingly, you, Sokrates, have no father.[52] [Footnote 52: Plato, Euthydêm. pp. 297-298.] But (retorts Ktesippus upon the couple) your father is different from my father.--Not at all.--How can that be?--What! is your father, then, the father of all men and of all animals?--Certainly he is. A man cannot be at the same time a father, and not a father. He cannot be at the same time a man, and not a man--gold, and not gold.[53]