The doctrine is contradicted (continues Sokrates) by the common opinions of mankind: for no man esteems himself a measure on all things. Every one believes that there are some things on which he is wiser than his neighbour — and others on which his neighbour is wiser than he. People are constantly on the look out for teachers and guides.50 If Protagoras advances an opinion which others declare to be false, he must, since he admits their opinion to be true, admit his own opinion to be false.51 No animal, nor any common man, is a measure; but only those men, who have gone through special study and instruction in the matter upon which they pronounce.52

In matters of present sentiment every man can judge for himself. Where future consequences are involved special knowledge is required.

In matters of present and immediate sensation, hot, cold, dry, moist, sweet, bitter, &c., Sokrates acknowledges that every man must judge for himself, and that what each pronounces is true for himself. So too, about honourable or base, just or unjust, holy or unholy — whatever rules any city may lay down, are true for itself: no man, no city, — is wiser upon these matters than any other.53 But in regard to what is good, profitable, advantageous, healthy, &c., the like cannot be conceded. Here (says Sokrates) one man, and one city, is decidedly wiser, and judges more truly, than another. We cannot say that the judgment of each is true;54 or that what every man or every city anticipates to promise good or profit, will necessarily realise such anticipations. In such cases, not merely present sentiment, but future consequences are involved.

Here then we discover the distinction which Plato would draw.55 Where present sentiment alone is involved, as in hot and cold, sweet and bitter, just and unjust, honourable and base, &c., there each is a judge for himself, and one man is no better judge than another. But where future consequences are to be predicted, the ignorant man is incapable: none but the professional Expert, or the prophet,56 is competent to declare the truth. When a dinner is on table, each man among the guests can judge whether it is good: but while it is being prepared, none but the cook can judge whether it will be good.57 This is one Platonic objection against the opinion of Protagoras, when he says that every opinion of every man is true. Another objection is, that opinions of different men are opposite and contradictory,58 some of them contradicting the Protagorean dictum itself.

Plato, when he impugns the doctrine of Protagoras, states that doctrine without the qualification properly belonging to it. All belief relative to the condition of the believing mind.

Such are the objections urged by Sokrates against the Protagorean doctrine — Homo Mensura. There may have been perhaps in the treatise of Protagoras, which unfortunately we do not possess, some reasonings or phrases countenancing the opinions against which Plato here directs his objections. But so far as I can collect, even from the words of Plato himself when he professes to borrow the phraseology of his opponent, I cannot think that Protagoras ever delivered the opinion which Plato here refutes — That every opinion of every man is true. The opinion really delivered by Protagoras appears to have been59 — That every opinion delivered by every man is true, to that man himself. But Plato, when he impugns it, leaves out the final qualification; falling unconsciously into the fallacy of passing (as logicians say) a dicto secundum quid ad dictum simpliciter.60 The qualification thus omitted by Plato forms the characteristic feature of the Protagorean doctrine, and is essential to the phraseology founded upon it. Protagoras would not declare any proposition to be true absolutely, or false absolutely. The phraseology belonging to that doctrine is forced upon him by Plato. Truth Absolute there is none, according to Protagoras. All truth is and must be truth relative to some one or more persons, either actually accepting and believing in it, or conceived as potential believers under certain circumstances. Moreover since these believers are a multitude of individuals, each with his own peculiarities — so no truth can be believed in, except under the peculiar measure of the believing individual mind. What a man adopts as true, and what he rejects as false, are conditioned alike by this limit: a limit not merely different in different individuals, but variable and frequently varying in the same individual. You cannot determine a dog, or a horse, or a child to believe in the Newtonian astronomy: you could not determine the author of the Principia in 1687 to believe what the child Newton had believed in 1647.61 To say that what is true to one man, is false to another — that what was true to an individual as a child or as a youth, becomes false to him in his advanced years, is no real contradiction: though Plato, by omitting the qualifying words, presents it as if it were such. In every man’s mind, the beliefs of the past have been modified or reversed, and the beliefs of the present are liable to be modified or reversed, by subsequent operative causes: by new supervening sensations, emotions, intellectual comparisons, authoritative teaching, or society, and so forth.

All exposition and discussion is an assemblage of individual judgments and affirmations. This fact is disguised by elliptical forms of language.

The fact, that all exposition and discussion is nothing more than an assemblage of individual judgments, depositions, affirmations, negations, &c, is disguised from us by the elliptical form in which it is conducted. For example:— I, who write this book — can give nothing more than my own report, as a witness, of facts known to me, and of what has been said, thought, or done by others, — for all which I cite authorities:— and my own conviction, belief or disbelief, as to the true understanding thereof, and the conclusions deducible. I produce the reasons which justify my opinion: I reply to those reasons which have been supposed by others to justify the opposite. It is for the reader to judge how far my reasons appear satisfactory to his mind.62 To deliver my own convictions, is all that is in my power: and if I spoke with full correctness and amplitude, it would be incumbent on me to avoid pronouncing any opinion to be true or false simply: I ought to say, it is true to me — or false to me. But to repeat this in every other sentence, would be a tiresome egotism. It is understood once for all by the title-page of the book: an opponent will know what he has to deal with, and will treat the opinions accordingly. If any man calls upon me to give him absolute truth, and to lay down the canon of evidence for identifying it — I cannot comply with the request, any farther than to deliver my own best judgment, what is truth — and to declare what is the canon of evidence which guides my own mind. Each reader must determine for himself whether he accepts it or not. I might indeed clothe my own judgments in oracular and vehement language: I might proclaim them as authoritative dicta: I might speak as representing the Platonic Ideal, Typical Man, — or as inspired by a δαίμων like Sokrates: I might denounce opponents as worthless men, deficient in all the sentiments which distinguish men from brutes, and meriting punishment as well as disgrace. If I used all these harsh phrases, I should only imitate what many authors of repute think themselves entitled to say, about THEIR beliefs and convictions. Yet in reality, I should still be proclaiming nothing beyond my own feelings:— the force of emotional association, and antipathy towards opponents, which had grown round these convictions in my own mind. Whether I speak in accordance with others, or in opposition to others, in either case I proclaim my own reports, feelings and judgments — nothing farther. I cannot escape from the Protagorean limit or measures.63

Argument — That the Protagorean doctrine equalises all men and animals. How far true. Not true in the sense requisite to sustain Plato’s objection.

To this theory Plato imputes as a farther consequence, that it equalises all men and all animals. No doubt, the measure or limit as generically described, bears alike upon all: but it does not mark the same degree in all. Each man’s bodily efforts are measured or limited by the amount of his physical force: this is alike true of all men: yet it does not follow that the physical force of all men is equal. The dog, the horse, the new-born child, the lunatic, is each a measure of truth to himself: the philosopher is so also to himself: this is alike true, whatever may be the disparity of intelligence: and is rather more obviously true when the disparity is great, because the lower intelligence has then a very narrow stock of beliefs, and is little modifiable by the higher. But though the Protagorean doctrine declares the dog or the child to be a measure of truth — each to himself — it does not declare either of them to be a measure of truth to me, to you, or to any ordinary by-stander. How far any person is a measure of truth to others, depends upon the estimation in which he is held by others: upon the belief which they entertain respecting his character or competence. Here is a new element let in, of which Plato, in his objection to the Protagorean doctrine, takes no account. When he affirms that Protagoras by his equalising doctrine acknowledged himself to be no better in point of wisdom and judgment than a dog or a child, this inference must be denied.64 The Protagorean doctrine is perfectly consistent with great diversities of knowledge, intellect, emotion, and character, between one man and another. Such diversities are recognised in individual belief and estimation, and are thus comprehended in the doctrine. Nor does Protagoras deny that men are teachable and modifiable. The scholar after being taught will hold beliefs different from those which he held before. Protagoras professed to know more than others, and to teach them: others on their side also believed that he knew more than they, and came to learn it. Such belief on both sides, noway contradicts the general doctrine here under discussion. What the scholar believes to be true, is still true to him: among those things which he believes to be true, one is, that the master knows more than he: in coming to be taught, he acts upon his own conviction. To say that a man is wise, is to say, that he is wise in some one’s estimation: your own or that of some one else. Such estimation is always implied, though often omitted in terms. Plato remarks very truly, that every one believes some others to be on certain matters wiser than himself. In other words, what is called authority — that predisposition to assent, with which we hear the statements and opinions delivered by some other persons — is one of the most operative causes in determining human belief. The circumstances of life are such as to generate this predisposition in every one’s mind to a greater or less degree, and towards some persons more than towards others.

Belief on authority is true to the believer himself — The efficacy of authority resides in the believer’s own mind.

Belief on authority is true to the believer himself, like all his other beliefs, according to the Protagorean doctrine: and in acting upon it, — in following the guidance of A, and not following the guidance of B, — he is still a measure to himself. It is not to be supposed that Protagoras ever admitted all men to be equally wise, though Plato puts such an admission into his mouth as an inference undeniable and obvious. His doctrine affirms something altogether different:— that whether you believe yourself to be wise or unwise, in either case the belief is equally your own — equally the result of your own mental condition and predisposition, — equally true to yourself, — and equally an item among the determining conditions of your actions. That the beliefs and convictions of one person might be modified by another, was a principle held by Protagoras not less than by Sokrates: the former employed as his modifying instrument, eloquent lecturing — the latter, dialectical cross-examination. Both of them recognise the belief of the person to whom they address themselves as true to him, yet at the same time as something which may be modified and corrected, by appealing to what they thought the better parts of it against the worse.

Protagorean formula — is false, to those who dissent from it.

Again — Sokrates imputes it as a contradiction to Protagoras — “Your doctrine is pronounced to be false by many persons: but you admit that the belief of all persons is true: therefore your doctrine is false”.65 Here also Plato omits the qualification annexed by Protagoras to his general principle — Every man’s belief is true — that is, true to him. That a belief should be true, to one man, and false to another — is not only no contradiction to the formula of Protagoras, but is the very state of things which his formula contemplates. He of course could only proclaim it as true to himself. It is the express purpose of his doctrine to disallow the absolutely true and the absolutely false. His own formula, like every other opinion, is false to those who dissent from it: but it is not false absolutely, any more than any other doctrine. Plato therefore does not make out his charge of contradiction.

Plato’s argument — That the wise man alone is a measure — Reply to it.

Some men (says Sokrates) have learnt, — have bestowed study on special matters, — have made themselves wise upon those matters. Others have not done the like, but remain ignorant. It is the wise man only who is a measure: the ignorant man neither is so, nor believes himself to be so, but seeks guidance from the wise.66

Upon this we may remark — First, that even when the untaught men are all put aside, and the erudites or Experts remain alone — still these very erudites or Experts, the men of special study, are perpetually differing among themselves; so that we cannot recognise one as a measure, without repudiating the authority of the rest.67 If by a measure, Plato means an infallible measure, he will not find it in this way: he is as far from the absolute as before. Next, it is perfectly correct that if any man be known to have studied or acquired experience on special matters, his opinion obtains an authority with others (more or fewer), such as the opinion of an ignorant man will not possess. This is a real difference between the graduated man and the non-graduated. But it is a difference not contradicting the theory of Protagoras; who did not affirm that every man’s opinion was equally trustworthy in the estimation of others, but that every man’s opinion was alike a measure to the man himself. The authority of the guide resides in the belief and opinion of those who follow him, or who feel prepared to follow him if necessity arises. A man gone astray on his journey, asks the way to his destination from residents whom he believes to know it, just as he might look at a compass, or at the stars, if no other persons were near. In following their direction, he is acting on his own belief, that he himself is ignorant on the point in question and that they know. He is a measure to himself, both of the extent of his own ignorance, and of the extent of his own knowledge. And in this respect all are alike — every man, woman, child, and animal;68 though they are by no means alike in the estimation of others, as trustworthy authorities.

Plato’s argument as to the distinction between present sensation and anticipation of the future.

The formula of Relativity does not imply that every man believes himself to be infallible.

I for my part admit this distinction to be real and important. Most other persons admit the same.69 In acting upon it, I follow out my belief, — and so do they. This is a general fact, respecting the circumstances which determine individual belief. Like all other causes of belief, it operates relatively to the individual mind, and thus falls under that general canon of relativity, which it is the express purpose of the Protagorean formula to affirm. Sokrates impugns the formula of relativity, as if it proclaimed every one to believe himself more competent to predict the future than any other person. But no such assumption is implied in it. To say that a man is a measure to himself, is not to say that he is, or, that he believes himself to be, omniscient or infallible. A sick man may mistake the road towards future health, in many different directions. One patient may over-estimate his own knowledge, — that is one way, but only one among several: another may be diffident, and may undervalue his own knowledge: a third may over-estimate the knowledge of his professional adviser, and thus follow an ignorant physician, believing him to be instructed and competent: a fourth, instead of consulting a physician, may consult a prophet, whom Plato70 here reckons among the authoritative infallible measures in respect to future events: a fifth may (like the rhetor Ælius Aristeides71) disregard the advice of physicians, and follow prescriptions enjoined to him in his own dreams, believing them to be sent by Æsculapius the Preserving God. Each of these persons judges differently about the road to future health: but each is alike a measure to himself: the belief of each is relative to his own mental condition and predispositions. You, or I, may believe that one or other of them is mistaken: but here another measure is introduced — your mind or mine.

Plato’s argument is untenable — That if the Protagorean formula be admitted, dialectic discussion would be annulled — The reverse is true — Dialectic recognises the autonomy of the Individual mind.

But the most unfounded among all Plato’s objections to the Protagorean formula, is that in which Sokrates is made to allege, that if it be accepted, the work of dialectical discussion is at an end: that the Sokratic Elenchus, the reciprocal scrutiny of opinions between two dialogists, becomes nugatory — since every man’s opinions are right.72 Instead of right, we must add the requisite qualification, here as elsewhere, by reading, right to the man himself. Now, dealing with Plato’s affirmation thus corrected, we must pronounce not only that it is not true, but that the direct reverse of it is true. Dialectical discussion and the Sokratic procedure, far from implying the negation of the Protagorean formula, involve the unqualified recognition of it. Without such recognition the procedure cannot even begin, much less advance onward to any result. Dialectic operates altogether by question and answer: the questioner takes all his premisses from the answers of the respondent, and cannot proceed in any direction except that in which the respondent leads him. Appeal is always directly made to the affirmative or negative of the individual mind, which is thus installed as measure of truth or falsehood for itself. The peculiar and characteristic excellence of the Sokratic Elenchus consists in thus stimulating the interior mental activity of the individual hearer, in eliciting from him all the positive elements of the debate, and in making him feel a shock when one of his answers contradicts the others. Sokrates not only does not profess to make himself a measure for the respondent, but expressly disclaims doing so: he protests against being considered as a teacher, and avows his own entire ignorance. He undertakes only the obstetric process of evolving from the respondent mind what already exists in it without the means of escape — and of applying interrogatory tests to the answer when produced: if there be nothing in the respondent’s mind, his art is inapplicable. He repudiates all appeal to authority, except that of the respondent himself.73 Accordingly there is neither sense nor fitness in the Sokratic cross-examination, unless you assume that each person, to whom it is addressed, is a measure of truth and falsehood to himself. Implicitly indeed, this is assumed in rhetoric as well as in dialectic: wherever the speaker aims at persuading, he adapts his mode of speech to the predispositions of the hearer’s own mind; and he thus recognises that mind as a measure for itself. But the Sokratic Dialectic embodies the same recognition, and the same essential relativity to the hearer’s mind, more forcibly than any rhetoric. And the Platonic Sokrates (in the Phædrus) makes it one of his objections against orators who addressed multitudes, that they did not discriminate either the specialties of different minds, or the specialties of discourse applicable to each.74