We have seen that an objective epistemology requires that a theory be free of arbitrary elements—that is, elements not required for cognition of reality. Concepts must be based on similarities and distinctions drawn from one's experience. Hypotheses must not posit existents or attributes that are not needed or suggested by any of that experience. This view is consistent with the common observation by scientists and philosophers that the simplest theory that fits the observed facts should be regarded as the best theory. This principle is known as "Occam's razor" (after William of Occam, also spelled "Ockham").

Many thinkers have interpreted this razor in metaphysical or even teleological terms, concluding that nature herself has an esthetic preference for the simple. In the Objectivist view presented here, however, the principle is recognized as an epistemological necessity—i. e., a logical requirement of man's knowledge. In fact, if we were to assume unnecessarily that nature (or "God") has a preference for simplicity, then that assumption would itself violate the razor principle!