"Concepts"= condensations of human knowledge, which also simultaneously transcend all human knowledge. They can never be overthrown - they are valid for all time. They exist only inside individual minds, but are also universal. (Yes, folks, it's a veritable all-you-can-eat-and-have-too cakefest!). Additionally, Rand hints that the true meaning of concepts can be properly determined only by superior men. In other words, Objectivism's version of Plato's Forms.