Aristotle (Soph. Elench.) attempts a classification of fallacies: Plato enumerates them without classification.

Fallacies of equivocation propounded by the two Sophists in the Euthydêmus.

Thus, for example, if we take the first sophism introduced by the two exhibitors, upon which they bring the youth Kleinias, by suitable questions, to declare successively both sides of the alternative — “Which of the two is it that learns, the wise or the ignorant?” — Sokrates himself elucidates it by pointing out that the terms used are equivocal:46 You might answer it by using the language ascribed to Dionysodorus in another part of this dialogue — “Neither and Both”.47 The like may be said about the fallacy in page 284 D — “Are there persons who speak of things as they are? Good men speak of things as they are: they speak of good men well, of bad men badly: therefore, of course, they speak of stout men stoutly, and of hot men hotly. Ay! rejoins the respondent Ktesippus, angrily — they speak of cold men coldly, and say that they talk coldly.”48 These are fallacies of double meaning of words — or double construction of phrases: as we read also in page 287 D, where the same Greek verb (νοεῖν) may be construed either to think or to mean: so that when Sokrates talks about what a predication means — the Sophists ask him — “Does anything think, except things having a soul? Did you ever know any predication that had a soul?”

Fallacies — à dicto secundum quid, ad dictum simpliciter — in the Euthydêmus.

Again, the two Sophists undertake to prove that Sokrates, as well as the youth Kleinias and indeed every one else, knows everything. “Can any existing thing be that which it is, and at the same time not be that which it is? — No. — You know some things? — Yes. — Then if you know, you are knowing? — Certainly. I am knowing of those particular things. — That makes no difference: if you are knowing, you necessarily know everything. — Oh! no: for there are many things which I do not know. — Then if there be anything which you do not know, you are not knowing? — Yes, doubtless — of that particular thing. — Still you are not knowing: and just now you said that you were knowing: and thus, at one and the same time, you are what you are, and you are not what you are.49

“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.”

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

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 (ἐπιστήμων). 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.

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

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

You have got a dog (Euthydêmus says to Ktesippus). — Yes. — The dog is the father of puppies? — Yes. — The dog, being a father, is yours? — Certainly. — Then your father is a dog, and you are brother of the puppies.

You beat your dog sometimes? Then you beat your father.54

Those animals, and those alone are yours (sheep, oxen, &c.), which you can give away, or sell, or sacrifice at pleasure. But Zeus, Apollo, and Athênê are your Gods. The Gods have a soul and are animals. Therefore your Gods are your animals. Now you told us that those alone were your animals, which you could give away, or sell, or sacrifice at pleasure. Therefore you can give away, or sell, or sacrifice at pleasure, Zeus, Apollo, and Athênê.55

This fallacy depends upon the double and equivocal meaning of yours — one of its different explanations being treated as if it were the only one.

Fallacies involving deeper logical principles — contradiction is impossible. — To speak falsely is impossible.

Other puzzles cited in this dialogue go deeper:— Contradiction is impossible — To speak falsely is impossible.56 These paradoxes were maintained by Antisthenes and others, and appear to have been matters of dialectic debate throughout the fourth and third centuries. I shall say more of them when I speak about the Megarics and Antisthenes. Here I only note, that in this dialogue, Ktesippus is represented as put to silence by them, and Sokrates as making an answer which is no answer at all.57 We see how much trouble these paradoxes gave to Plato, when we read the Sophistês, in which he handles the last of the two in a manner elaborate, but (to my judgment) unsatisfactory.

Plato’s Euthydêmus is the earliest known attempt to set out and expose fallacies — the only way of exposing fallacies is to exemplify the fallacy by particular cases, in which the conclusion proved is known aliunde to be false and absurd.

The Euthydêmus of Plato is memorable in the history of philosophy as the earliest known attempt to set out, and exhibit to attention, a string of fallacious modes of reasoning. Plato makes them all absurd and ridiculous. He gives a caricature of a dialectic debate, not unworthy of his namesake Plato Comicus — or of Aristophanes, Swift, or Voltaire. The sophisms appear for the most part so silly, as he puts them, that the reader asks himself how any one could have been ever imposed upon by such a palpable delusion? Yet such confidence is by no means justified. A sophism, perfectly analogous in character to those which Plato here exposes to ridicule, may, in another case, easily escape detection from the hearer, and even from the reasoner himself. People are constantly misled by fallacies arising from the same word bearing two senses, from double construction of the same phrase, from unconscious application of a dictum secundum quid, as if it were a dictum simpliciter; from Petitio Principii, &c., Ignoratio Elenchi, &c. Neither Plato himself, nor Aristotle, can boast of escaping them.58 If these fallacies appear, in the examples chosen by Plato for the Euthydêmus, so obviously inconclusive that they can deceive no one — the reason lies not in the premisses themselves, but in the particular conclusions to which they lead: which conclusions are known on other grounds to be false, and never to be seriously maintainable by any person. Such conclusions as — “Sokrates had no father: Sophroniskus, if father of Sokrates, was father of all men and all animals: In beating your dog, you beat your father: If you know one thing, you know everything,” &c., being known aliunde to be false, prove that there has been some fallacy in the premisses whereby they have been established. Such cases serve as a reductio ad absurdum of the antecedent process. They make us aware of one mode of liability to error, and put us on our guard against it in analogous cases. This is a valuable service, and all the more valuable, because the liability to error is real and widespread, even from fallacies perfectly analogous to those which seem so silly under the particular exemplifications which Plato selects and exposes. Many of the illustrations of the Platonic Euthydêmus are reproduced by Aristotle in the Treatise de Sophisticis Elenchis, together with other fallacies, discriminated with a certain method and system.59

Mistake of supposing fallacies to have been invented and propagated by Athenian Sophists — they are inherent inadvertencies and liabilities to error, in the ordinary process of thinking. Formal debate affords the best means of correcting them.

This view of the case appears to me incomplete and misleading. It substitutes the rare and accidental in place of the constant and essential. The various sophisms, of which Plato in the Euthydêmus gives the reductio ad absurdum, are not the inventions of Sophists. They are erroneous tendencies of the reasoning process, frequently incident to human thought and speech: specimens of those ever-renewed “inadvertencies of ordinary thinking” (to recur to a phrase cited in my preface), which it is the peculiar mission of philosophy or “reasoned truth” to rectify. Moreover the practice of formal debate, which is usually denounced with so much asperity — if it affords on some occasions opportunity to produce such fallacies, presents not merely equal opportunity, but the only effective means, for exposing and confuting them. Whately in his Logic,60 like Plato in the Euthydêmus, when bringing these fallacies into open daylight in order that every one may detect them, may enliven the theme by presenting them as the deliberate tricks of a Sophist. Doubtless they are so by accident: yet their essential character is that of infirmities incident to the intellectus sibi permissus: operative at Athens before Athenian Sophists existed, and in other regions also, where these persons never penetrated.

Wide-spread prevalence of erroneous belief, misguided by one or other of these fallacies, attested by Sokrates, Plato, Bacon, &c., — complete enumeration of heads of fallacies by Mill.

The wide diffusion and constant prevalence of such infirmities is attested not less by Sokrates in his last speech, wherein he declares real want of knowledge and false persuasion of knowledge, to be universal, the mission of his life being to expose them, though he could not correct them — than by Bacon in his reformatory projects, where he enumerates the various Idola worshipped by the human intellect, and the false tendencies acquired “in primâ digestione mentis“. The psychological analysis of the sentiment of belief with its different sources, given in Mr. Alexander Bain’s work on the Emotions and the Will, shows how this takes place; and exhibits true or sound belief, in so far as it ever is acquired, as an acquisition only attained after expulsion of earlier antecedent error.61 Of such error, and of the different ways in which apparent evidence is mistaken for real evidence, a comprehensive philosophical exposition is farther given by Mr. John Stuart Mill, in the fifth book of his System of Logic, devoted to the subject of Fallacies. Every variety of erroneous procedure is referable to some one or more of the general heads of Fallacy there enumerated. It is the Fallacies of Ratiocination, of which the two Sophists, in the Platonic Euthydêmus, are made to exhibit specimens: and when we regard such Fallacies, as one branch among several in a complete logical scheme, we shall see at once that they are not inventions of the Athenian Sophists — still less inventions for the purpose of Eristic or formal debate. For every one of these Fallacies is of a nature to ensnare men, and even to ensnare them more easily, in the common, informal, conversation of life — or in their separate thoughts. Besides mistakes on matters of fact, the two main causes which promote the success and encourage the multiplication of Fallacies generally, are first, the emotional bias towards particular conclusions, which disposes persons to accept any apparent evidence, favourable to such conclusion, as if it, were real evidence: next, the careless and elliptical character of common speech, in which some parts of the evidence are merely insinuated, and other parts altogether left out. It is this last circumstance which gives occasion to the very extensive class of Fallacies called by Mr. Mill Fallacies of Confusion: a class so large, that the greater number of Fallacies might plausibly be brought under it.62

Value of formal debate as a means for testing and confuting fallacies.

We thus see not only that the fallacious agencies are self-operative, generating their own weeds in the common soil of human thought and speech, without being planted by Athenian Sophists or watered by Eristic — but that this very Eristic affords the best means of restraining their diffusion. It is only in formal debate that the disputant can be forced to make clear to himself and declare explicitly to others, without reserve or omission, all the premisses upon which his conclusion rests — that every part of these premisses becomes liable to immediate challenge by an opponent — that the question comes distinctly under consideration, what is or is not sufficient evidence — that the premisses of one argument can be compared with the premisses of another, so that if in the former you are tempted to acquiesce in them as sufficient because you have a bias favourable to the conclusion, in the latter you may be made to feel that they are insufficient, because the conclusion which they prove is one which you know to be untrue (reductio ad absurdum). The habit of formal debate (called by those who do not like it, Eristic63) is thus an indispensable condition both for the exposure and confutation of fallacies, which exist quite independent of that habit — owing their rise and prevalence to deep-seated psychological causes.

Without the habit of formal debate, Plato could not have composed his Euthydêmus, nor Aristotle the treatise De Sophisticis Elenchis.

Without the experience acquired by this habit of dialectic debate at Athens, Plato could not have composed his Euthydêmus, exhibiting a reductio ad absurdum of several verbal fallacies — nor could we have had the logical theories of Aristotle, embodied in the Analytica and Topica with its annexed treatise De Sophisticis Elenchis, in which various fallacies are discriminated and classified. These theories, and the corollaries connected with them, do infinite honour to the comprehensive intellect of Aristotle: but he could not have conceived them without previous study of the ratiocinative process. He, as the first theorizer, must have had before him abundant arguments explicitly laid out, and contested, or open to be contested, at every step by an opponent.64 Towards such habit of formal argumentation, a strong repugnance was felt by many of the Athenian public, as there is among modern readers generally: but those who felt thus, had probably little interest in the speculations either of Plato or of Aristotle. That the Platonic critics should themselves feel this same repugnance, seems to me not consistent with their admiration for the great dialectician and logician of antiquity: nor can I at all subscribe to their view, when they present to us the inherent infirmities of the human intellect as factitious distempers generated by the habit of formal debate, and by the rapacity of Protagoras, Prodikus, and others.

Probable popularity of the Euthydêmus at Athens — welcomed by all the enemies of Dialectic.

I think it probable that the dialogue of Euthydêmus, as far as the point to which I have brought it (i.e., where Sokrates finishes his recital to Kriton of the conversation which he had had with the two Sophists), was among the most popular of all the Platonic dialogues: not merely because of its dramatic vivacity and charm of expression, but because it would be heartily welcomed by the numerous enemies of Dialectic at Athens. We must remember that in the estimation of most persons at Athens, Dialectic included Sokrates and all the viri Sokratici (Plato among them), just as much as the persons called Sophists. The discreditable picture here given of Euthydêmus and Dionysodorus, would be considered as telling against Dialectic and the Sokratic Elenchus generally: while the rhetors, and others who dealt in long continuous discourse, would treat it as a blow inflicted upon the rival art of dialogue, by the professor of the dialogue himself. In Plato’s view, the dialogue was the special and appropriate manifestation of philosophy.

Epilogue of Plato to the Dialogue, trying to obviate this inference by opponents — Conversation between Sokrates and Kriton.

That the natural effect of the picture here drawn by Plato, was, to justify the antipathy of those who hated philosophy — we may see by the epilogue which Plato has thought fit to annex: an epilogue so little in harmony with what has preceded, that we might almost imagine it to be an afterthought — yet obviously intended to protect philosophy against imputations. Sokrates having concluded the recital, in his ironical way, by saying that he intended to become a pupil under the two Sophists, and by inviting Kriton to be a pupil along with him — Kriton replies by saying that he is anxious to obtain instruction from any one who can give it, but that he has no sympathy with Euthydêmus, and would rather be refuted by him, than learn from him to refute in such a manner. Kriton proceeds to report to Sokrates the remarks of a by-stander (an able writer of discourses for the Dikastery) who had heard all that passed; and who expressed his surprise that Sokrates could have remained so long listening to such nonsense, and manifesting so much deference for a couple of foolish men. Nevertheless (continued the by-stander) this couple are among the most powerful talkers of the day upon philosophy. This shows you how worthless a thing philosophy is: prodigious fuss, with contemptible result — men careless what they say, and carping at every word that they hear.65

Now, Sokrates (concludes Kriton), this man is wrong for depreciating philosophy, and all others who depreciate it are wrong also. But he was right in blaming you, for disputing with such a couple before a large crowd.

Sokr. — What kind of person is this censor of philosophy? Is he a powerful speaker himself in the Dikastery? Or is he only a composer of discourses to be spoken by others? Krit. — The latter. I do not think that he has ever spoken in court: but every one says that he knows judicial practice well, and that he composes admirable speeches.66

Altered tone in speaking of Euthydêmus — Disparagement of persons half-philosophers, half-politicians.

Sokr. — I understand the man. He belongs to that class whom Prodikus describes as the border-men between philosophy and politics. Persons of this class account themselves the wisest of mankind, and think farther that besides being such in reality, they are also admired as such by many: insomuch that the admiration for them would be universal, if it were not for the professors of philosophy. Accordingly they fancy, that if they could once discredit these philosophers, the prize of glory would be awarded to themselves, without controversy, by every one: they being in truth the wisest men in society, though liable, if ever they are caught in dialectic debate, to be overpowered and humbled by men like Euthydêmus.67 They have very plausible grounds for believing in their own wisdom, since they pursue both philosophy and politics to a moderate extent, as far as propriety enjoins; and thus pluck the fruit of wisdom without encountering either dangers or contests. Krit. — What do you say to their reasoning, Sokrates? It seems to me specious. Sokr. — Yes, it is specious, but not well founded. You cannot easily persuade them, though nevertheless it is true, that men who take a line mid-way between two pursuits, are better than either, if both pursuits be bad — worse than either, if both pursuits be good, but tending to different ends — better than one and worse than the other, if one of the pursuits be bad and the other good — better than both, if both be bad, but tending to different ends. Such being the case, if the pursuit of philosophy and that of active politics be both of them good, but tending to different objects, these men are inferior to the pursuers of one as well as of the other: if one be good, the other bad, they are worse than the pursuers of the former, better than the pursuers of the latter: if both be bad, they are better than either. Now I am sure that these men themselves account both philosophy and politics to be good. Accordingly, they are inferior both to philosophers and politicians:68 they occupy only the third rank, though they pretend to be in the first. While we pardon such a pretension, and refrain from judging these men severely, we must nevertheless recognise them for such as they really are. We must be content with every one, who announces any scheme of life, whatever it be, coming within the limits of intelligence, and who pursues his work with persevering resolution.69

Kriton asks Sokrates for advice about the education of his sons — Sokrates cannot recommend a teacher — tells him to search for himself.

Krit. I am always telling you, Sokrates, that I too am embarrassed where to seek instructors for my sons. Conversation with you has satisfied me, that it is madness to bestow so much care upon the fortune and position of sons, and so little upon their instruction. Yet when I turn my eyes to the men who make profession of instructing, I am really astonished. To tell you the truth, every one of them appears to me extravagantly absurd,70 so that I know not how to help forward my son towards philosophy. Sokr. — Don’t you know, Kriton, that in every different pursuit, most of the professors are foolish and worthless, and that a few only are excellent and above price? Is not this the case with gymnastic, commercial business, rhetoric, military command? Are not most of those who undertake these pursuits ridiculously silly?71 Krit. — Unquestionably: nothing can be more true. Sokr. — Do you think that a sufficient reason for avoiding all these pursuits yourself, and keeping your son out of them also? Krit. No: it would be wrong to do so. Sokr. — Well then, don’t do so. Take no heed about the professors of philosophy, whether they are good or bad; but test philosophy itself, well and carefully. If it shall appear to you worthless, dissuade not merely your sons, but every one else also, from following it.72 But if it shall appear to you as valuable as I consider it to be, then take courage to pursue and practise it, you and your children both, according to the proverb. —