There are such things as invalid concepts, i.e., words that represent attempts to integrate errors, contradictions or false propositions, such as concepts originating in mysticism—or words without specific definitions, without referents, which can mean anything to anyone, such as modern “anti-concepts.” Invalid concepts appear occasionally in men’s languages, but are usually—though not necessarily—short-lived, since they lead to cognitive dead-ends. An invalid concept invalidates every proposition or process of thought in which it is used as a cognitive assertion.

No concept man forms is valid unless he integrates it without contradiction into the total sum of his knowledge.

“Galt’s Speech”
For the New Intellectual, 126
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