"Any theory that propounds an opposition between the logical and the empirical, represents a failure to grasp the nature of logic and its role in human cognition. Man’s knowledge is not acquired by logic apart from experience or by experience apart from logic, but by the application of logic to experience. All truths are the product of a logical identification of the facts of experience.

Man is born tabula rasa; all his knowledge is based on and derived from the evidence of his senses. To reach the distinctively human level of cognition, man must conceptualize his perceptual data — and conceptualization is a process which is neither automatic nor infallible. Man needs to discover a method to guide this process, if it is to yield conclusions which correspond to the facts of reality — i.e., which represent knowledge. The principle at the base of the proper method is the fundamental principle of metaphysics: the Law of Identity. In reality, contradictions cannot exist; in a cognitive process, a contradiction is the proof of an error. Hence the method man must follow: to identify the facts he observes, in a non-contradictory manner. This method is logic — “the art of non-contradictory identification.” (Atlas Shrugged.) Logic must be employed at every step of a man’s conceptual development, from the formation of his first concepts to the discovery of the most complex scientific laws and theories. Only when a conclusion is based on a non-contradictory identification and integration of all the evidence available at a given time, can it qualify as knowledge.

The failure to recognize that logic is man’s method of cognition, has produced a brood of artificial splits and dichotomies which represent restatements of the analytic-synthetic dichotomy from various aspects. Three in particular are prevalent today: logical truth vs. factual truth; the logically possible vs. the empirically possible; and the a priori vs. the a posteriori.

The logical-factual dichotomy opposes truths which are validated “merely” by the use of logic (the analytic ones), and truths which describe the facts of experience (the synthetic ones). Implicit in this dichotomy is the view that logic is a subjective game, a method of manipulating arbitrary symbols, not a method of acquiring knowledge.

It is the use of logic that enables man to determine what is and what is not a fact. To introduce an opposition between the “logical” and the “factual” is to create a split between consciousness and existence, between truths in accordance with man’s method of cognition and truths in accordance with the facts of reality. The result of such a dichotomy is that logic is divorced from reality (“Logical truths are empty and conventional”) — and reality becomes unknowable (“Factual truths are contingent and uncertain”). This amounts to the claim that man has no method of cognition, i.e., no way of acquiring knowledge."

Ayn Rand, Introduction to Objectivist Epistemology, 112–113