“We know that we know nothing,” they chatter, blanking out the fact that they are claiming knowledge — “There are no absolutes,” they chatter, blanking out the fact that they are uttering an absolute — “You cannot prove that you exist or that you’re conscious,” they chatter, blanking out the fact that proof presupposes existence, consciousness and a complex chain of knowledge: the existence of something to know, of a consciousness able to know it, and of a knowledge that has learned to distinguish between such concepts as the proved and the unproved.

“Galt’s Speech”
For the New Intellectual, 154

In the history of philosophy — with some very rare exceptions — epistemological theories have . . . taught either that knowledge is impossible (skepticism) or that it is available without effort (mysticism). These two positions appear to be antagonists, but are, in fact, two variants on the same theme, two sides of the same fraudulent coin: the attempt to escape the responsibility of rational cognition and the absolutism of reality — the attempt to assert the primacy of consciousness over existence. . . .

The mystic is usually an exponent of the intrinsic (revealed) school of epistemology; the skeptic is usually an advocate of epistemological subjectivism.

The crusading skepticism of the modern era; the mounting attack on absolutes, certainty, reason itself; the insistence that firm convictions are a disease and that compromise in any dispute is men’s only recourse — all this, in significant part, is an outgrowth of Descartes’ basic approach to philosophy. To reclaim the self-confidence of man’s mind, the first modern to refute is Kant (see [Introduction to Objectivist Epistemology][11]); the second is Descartes.

Observe that Descartes starts his system by using “error” and its synonyms or derivatives as “stolen concepts.”

Men have been wrong, and therefore, he implies, they can never know what is right. But if they cannot, how did they ever discover that they were wrong? How can one form such concepts as “mistake” or “error” while wholly ignorant of what is correct? “Error” signifies a departure from truth; the concept of “error” logically presupposes that one has already grasped some truth. If truth were unknowable, as Descartes implies, the idea of a departure from it would be meaningless.

The same point applies to concepts denoting specific forms of error. If we cannot ever be certain that an argument is logically valid, if validity is unknowable, then the concept of “invalid” reasoning is impossible to reach or apply. If we cannot ever know that a man is sane, then the concept of “insanity” is impossible to form or define. If we cannot recognize the state of being awake, then we cannot recognize or conceptualize a state of not being awake (such as dreaming). If man cannot grasp X, then “non-X” stands for nothing.

Fallibility does not make knowledge impossible. Knowledge is what makes possible the discovery of fallibility.

Leonard Peikoff, “‘Maybe You’re Wrong’”
The Objectivist Forum, April 1981, 8

It is possible, the skeptic argument declares, for man to be in error; therefore, it is possible that every individual is in error on every question. This argument is a non sequitur; it is an equivocation on the term “possible.”

What is possible to a species under some circumstances, is not necessarily possible to every individual member of that species under every set of circumstances. Thus, it is possible for a human being to run the mile in less than four minutes; and it is possible for a human being to be pregnant. I cannot, however, go over to a crippled gentleman in his wheelchair and say: “Perhaps you’ll give birth to a son next week, after you’ve run the mile to the hospital in 3.9 minutes — after all, you’re human, and it is possible for human beings to do these things.”

The same principle applies to the possibility of error — or of truth. If someone maintains that New York City is made of mushroom soup, he cannot defend his idea by saying: “It is possible for human beings to reach the truth, I am human, so maybe this is the truth.” No matter what is possible under some conditions, a man cannot be “possibly” right when he is blatantly wrong. By the same token, no skeptic can declare that you are possibly wrong, when you are blatantly right. “It is possible for man . . . ” does not justify “It is possible that you . . . ” The latter claim depends on the individual involved, and on the conditions.

“Maybe you’re wrong” is an accusation that must be supported by specific evidence. It cannot be uttered without context, grounds, or basis, i.e., arbitrarily.

Leonard Peikoff, “‘Maybe You’re Wrong’”
The Objectivist Forum, April 1981, 10

Doubting without a basis is the equivalent of — is indeed a form of — asserting without a basis. Both procedures, being arbitrary, are disqualified by the very nature of human cognition. In reason, certainty must precede doubt, just as a grasp of truth must precede the detection of error. To establish a claim to knowledge, what one must do is to prove an idea positively, on the basis of the full context of evidence available; i.e., a man must prove that he is right. It is not incumbent on anyone — nor is it possible — to prove that he is not wrong, when no evidence of error has been offered.

Leonard Peikoff, “‘Maybe You’re Wrong’”
The Objectivist Forum, April 1981, 12
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