Fallacy of the stolen concept

The fallacy of the stolen concept is the error of using a concept while denying the more fundamental concepts it depends on. The term is Ayn Rand's, and the fallacy is distinctive because it is not merely false but self-eliminating: the act of asserting it presupposes what the assertion denies.

“The stolen concept fallacy consists in using a concept while denying the validity of its genetic roots, i.e., of the earlier concepts on which it logically depends.”
~ Nathaniel Branden, "The Stolen Concept", The Objectivist Newsletter, 1963

Why concepts have roots

Conceptual knowledge is hierarchical. Concepts are formed from earlier concepts, which are formed from still earlier ones, and the chain ultimately rests on the perceptually given. "Justice" cannot be grasped without "action", "man" and "value"; "inflation" cannot be grasped without "money". See Hierarchy and Concept formation.

A concept therefore carries its ancestry with it. To deny a concept at the base of the chain is to destroy every concept above it — including the ones being used to make the denial. This is what distinguishes the stolen concept from an ordinary false statement. A false statement can be examined and refuted; a stolen concept dismantles the terms in which the examination would be conducted.

Rand compared it to the classical fallacy of assuming what one is supposed to prove, with the sign reversed: it is assuming what one overtly denies.

Standard examples

"Property is theft." Proudhon's slogan. "Theft" means taking what rightfully belongs to another, so the concept presupposes property rights. If there were no property, there could be no theft, and the sentence would have nothing to say.
"All knowledge is uncertain." Offered as something known with certainty. See Skepticism and Certainty.
"Reason is invalid." The claim is put forward as a conclusion, supported by argument, and asks to be accepted because it is logical. See Reason and Logic.
"Existence does not exist" or "identity is an illusion" — an existent using a consciousness to assert something definite, which is what makes the axioms irrefutable. Objectivism calls this validation by reaffirmation through denial.
"Man has no free will, so nobody should be blamed." "Should" presupposes the capacity to have chosen otherwise. See Determinism and Volition.

Its relation to context-dropping

The stolen concept is the most serious form of a wider error: dropping the context that gave a concept its meaning. A concept is valid within the body of knowledge that produced it, and detaching it from that body leaves a word whose remaining content is whatever the speaker supplies. See Floating Abstraction and Package-Deal.

Identifying a stolen concept is therefore done by reduction — tracing the disputed term down the hierarchy until the presupposed concept appears. What makes the fallacy hard to spot is that the denial is usually stated at a high level of abstraction, several steps above the concept it destroys.

Common misunderstandings

That it is a way of winning arguments by definition. The charge has to be demonstrated by exhibiting the actual dependency, not asserted. Showing that a term feels related is not enough.
That any use of a contested term commits it. Arguing that a concept is invalid, and giving reasons stated in terms that do not depend on it, is legitimate philosophy. The fallacy occurs only when the denial is made in the very terms it would destroy.
That it is the same as circular reasoning. Circularity smuggles the conclusion into the premises. This fallacy denies the premises while relying on the conclusion.
That it applies only to philosophy. It appears wherever a specialised concept is used against its own foundation — most commonly in political argument, where the terms are furthest from their perceptual base.

Discussion

References

Branden, Nathaniel. "The Stolen Concept", The Objectivist Newsletter, January 1963.
Rand, Ayn. Introduction to Objectivist Epistemology. 2nd edition, Meridian, 1990.
Peikoff, Leonard. Objectivism: The Philosophy of Ayn Rand, chapter 1.