“He [the devil] always sends errors into the world in pairs—pairs of opposites. And he always encourages us to spend a lot of time thinking which is the worse. You see why, of course? He relies on your extra dislike of the one error to draw you gradually into the opposite one. But do not let us be fooled. We have to keep our eyes on the goal and go straight through between both errors. We have no other concern than that with either of them.”

Preface
The Screwtape Letters (1942)
Context: There are two equal and opposite errors into which our race can fall about the devils. One is to disbelieve in their existence. The other is to believe, and to feel an excessive and unhealthy interest in them. They themselves are equally pleased by both errors and hail a materialist or a magician with the same delight.

Source: 1950s, My Philosophical Development (1959), pp. 93-93

Our Future
Alain On Happiness (1928)

Source: After the Cataclysm: Postwar Indochina and the Reconstruction of Imperial Ideology, with Noam Chomsky, 1979, p. 256.

Report on Manufactures (1791)
Context: It is not uncommon to meet with an opinion that though the promoting of manufactures may be the interest of a part of the Union, it is contrary to that of another part. The Northern & Southern regions are sometimes represented as having adverse interests in this respect. Those are called Manufacturing, these Agricultural states; and a species of opposition is imagined to subsist between the Manufacturing and Agricultural interests. This idea of an opposition between those two interests is the common error of the early periods of every country, but experience gradually dissipates it. Indeed they are perceived so often to succour and to befriend each other, that they come at length to be considered as one. (...) Perhaps the superior steadiness of the demand of a domestic market for the surplus produce of the soil, is alone a convincing argument of its truth.

The Origins of Knowledge and Imagination (1978)

American Communications Association v. Douds, 339 U.S. 382, 442-43 (1950)
Judicial opinions
Context: The priceless heritage of our society is the unrestricted constitutional right of each member to think as he will. Thought control is a copyright of totalitarianism, and we have no claim to it. It is not the function of the government to keep the citizen from falling into error; it is the function of the citizen to keep the government from falling into error. We could justify any censorship only when the censors are better shielded against error than the censored.

Source: 1920s, Prejudices, Third Series (1922), Ch. 3 "Footnote on Criticism", pp. 85-104
Context: Truth, indeed, is something that is believed in completely only by persons who have never tried personally to pursue it to its fastness and grab it by the tail. It is the adoration of second-rate men — men who always receive it as second-hand. Pedagogues believe in immutable truths and spend their lives trying to determine them and propagate them; the intellectual progress of man consists largely of a concerted effort to block and destroy their enterprise. Nine times out of ten, in the arts as in life, there is actually no truth to be discovered; there is only error to be exposed. In whole departments of human inquiry it seems to me quite unlikely that the truth ever will be discovered. Nevertheless, the rubber-stamp thinking of the world always makes the assumption that the exposure of an error is identical with the discovery of truth — that error and truth are simply opposites. They are nothing of the sort. What the world turns to, when it has been cured of one error, is usually simply another error, and maybe one worse than the first one. This is the whole history of the intellect in brief. The average man of today does not believe in precisely the same imbecilities that the Greek of the Fourth Century before Christ believed in, but the things that he does believe in are often quite as idiotic.
Perhaps this statement is a bit too sweeping. There is, year by year, a gradual accumulation of what may be called, provisionally, truths — there is a slow accretion of ideas that somehow manage to meet all practicable human tests, and so survive. But even so, it is risky to call them absolute truths. All that one may safely say of them is that no one, as yet, has demonstrated that they are errors. Soon or late, if experience teaches us anything, they are likely to succumb too. The profoundest truths of the Middle Ages are now laughed at by schoolboys. The profoundest truths of democracy will be laughed at, a few centuries hence, even by school-teachers.

Vol. I; I
Lacon (1820)