[Objectivism agrees with Aristotle’s formulation of the Law of
Non-Contradiction]: These truths hold good for everything that is, and not for
some special genus apart from others. And all men use them, because they are
true of being qua being . . . . For a principle which everyone must have who
understands anything that is, is not a hypothesis . . . . Evidently then such a
principle is the most certain of all; which principle this is, let us proceed
to say. It is, that the same attribute cannot at the same time belong and not
belong to the same subject and in the same respect.