If there are any persons who contest a received opinion, or who will do so if law or opinion will let them, let us thank them for it

From On Liberty by John Stuart Mill. Chapter II “Of the Liberty of Thought and Discussion,” from the middle of paragraph 29.

There are many reasons, doubtless, why doctrines which are the badge of a sect retain more of their vitality than those common to all recognised sects, and why more pains are taken by teachers to keep their meaning alive; but one reason certainly is, that the peculiar doctrines are more questioned, and have to be oftener defended against open gainsayers. Both teachers and learners go to sleep at their post, as soon as there is no enemy in the field.

The same thing holds true, generally speaking, of all traditional doctrines—those of prudence and knowledge of life, as well as of morals or religion. All languages and literatures are full of general observations on life, both as to what it is, and how to conduct oneself in it; observations which everybody knows, which everybody repeats, or hears with acquiescence, which are received as truisms, yet of which most people first truly learn the meaning, when experience, generally of a painful kind, has made it a reality to them. How often, when smarting under some unforeseen misfortune or disappointment, does a person call to mind some proverb or common saying, familiar to him all his life, the meaning of which, if he had ever before felt it as he does now, would have saved him from the calamity. There are indeed reasons for this, other than the absence of discussion: there are many truths of which the full meaning cannot be realized, until personal experience has brought it home. But much more of the meaning even of these would have been understood, and what was understood would have been far more deeply impressed on the mind, if the man had been accustomed to hear it argued pro and con by people who did understand it. The fatal tendency of mankind to leave off thinking about a thing when it is no longer doubtful, is the cause of half their errors. A contemporary author has well spoken of “the deep slumber of a decided opinion.”

But what! (it may be asked) Is the absence of unanimity an indispensable condition of true knowledge? Is it necessary that some part of mankind should persist in error, to enable any to realize the truth? Does a belief cease to be real and vital as soon as it is generally received—and is a proposition never thoroughly understood and felt unless some doubt of it remains? As soon as mankind have unanimously accepted a truth, does the truth perish within them? The highest aim and best result of improved intelligence, it has hitherto been thought, is to unite mankind more and more in the acknowledgment of all important truths: and does the intelligence only last as long as it has not achieved its object? Do the fruits of conquest perish by the very completeness of the victory?

I affirm no such thing. As mankind improve, the number of doctrines which are no longer disputed or doubted will be constantly on the increase: and the well-being of mankind may almost be measured by the number and gravity of the truths which have reached the point of being uncontested. The cessation, on one question after another, of serious controversy, is one of the necessary incidents of the consolidation of opinion; a consolidation as salutary in the case of true opinions, as it is dangerous and noxious when the opinions are erroneous. But though this gradual narrowing of the bounds of diversity of opinion is necessary in both senses of the term, being at once inevitable and indispensable, we are not therefore obliged to conclude that all its consequences must be beneficial. The loss of so important an aid to the intelligent and living apprehension of a truth, as is afforded by the necessity of explaining it to, or defending it against, opponents, though not sufficient to outweigh, is no trifling drawback from, the benefit of its universal recognition. Where this advantage can no longer be had, I confess I should like to see the teachers of mankind endeavouring to provide a substitute for it; some contrivance for making the difficulties of the question as present to the learner’s consciousness, as if they were pressed upon him by a dissentient champion, eager for his conversion.

But instead of seeking contrivances for this purpose, they have lost those they formerly had. The Socratic dialectics, so magnificently exemplified in the dialogues of Plato, were a contrivance of this description. They were essentially a negative discussion of the great questions of philosophy and life, directed with consummate skill to the purpose of convincing any one who had merely adopted the commonplaces of received opinion, that he did not understand the subject—that he as yet attached no definite meaning to the doctrines he professed; in order that, becoming aware of his ignorance, he might be put in the way to attain a stable belief, resting on a clear apprehension both of the meaning of doctrines and of their evidence. The school disputations of the middle ages had a somewhat similar object. They were intended to make sure that the pupil understood his own opinion, and (by necessary correlation) the opinion opposed to it, and could enforce the grounds of the one and confute those of the other. These last-mentioned contests had indeed the incurable defect, that the premises appealed to were taken from authority, not from reason; and, as a discipline to the mind, they were in every respect inferior to the powerful dialectics which formed the intellects of the “Socratici viri:” but the modern mind owes far more to both than it is generally willing to admit, and the present modes of education contain nothing which in the smallest degree supplies the place either of the one or of the other. A person who derives all his instruction from teachers or books, even if he escape the besetting temptation of contenting himself with cram, is under no compulsion to hear both sides; accordingly it is far from a frequent accomplishment, even among thinkers, to know both sides; and the weakest part of what everybody says in defence of his opinion, is what he intends as a reply to antagonists. It is the fashion of the present time to disparage negative logic—that which points out weaknesses in theory or errors in practice, without establishing positive truths. Such negative criticism would indeed be poor enough as an ultimate result; but as a means to attaining any positive knowledge or conviction worthy the name, it cannot be valued too highly; and until people are again systematically trained to it, there will be few great thinkers, and a low general average of intellect, in any but the mathematical and physical departments of speculation. On any other subject no one’s opinions deserve the name of knowledge, except so far as he has either had forced upon him by others, or gone through of himself, the same mental process which would have been required of him in carrying on an active controversy with opponents. That, therefore, which when absent, it is so indispensable, but so difficult, to create, how worse than absurd is it to forego, when spontaneously offering itself! If there are any persons who contest a received opinion, or who will do so if law or opinion will let them, let us thank them for it, open our minds to listen to them, and rejoice that there is some one to do for us what we otherwise ought, if we have any regard for either the certainty or the vitality of our convictions, to do with much greater labor for ourselves.