Since consciousness is a specific faculty, it has a specific nature or identity and, therefore, its range is limited: it cannot perceive everything at once; since awareness, on all its levels, requires an active process, it cannot do everything at once. Whether the units with which one deals are percepts or concepts, the range of what man can hold in the focus of his conscious awareness at any given moment, is limited. The essence, therefore, of man’s incomparable cognitive power is the ability to reduce a vast amount of information to a minimal number of units — which is the task performed by his conceptual faculty. And the principle of unit-economy is one of that faculty’s essential guiding principles.

“The Cognitive Role of Concepts”
Introduction to Objectivist Epistemology, 63

In any given moment, concepts enable man to hold in the focus of his conscious awareness much more than his purely perceptual capacity would permit. The range of man’s perceptual awareness — the number of percepts he can deal with at any one time — is limited. He may be able to visualize four or five units — as, for instance, five trees. He cannot visualize a hundred trees or a distance of ten light-years. It is only his conceptual faculty that makes it possible for him to deal with knowledge of that kind.

Conceptualization is a method of expanding man’s consciousness by reducing the number of its content’s units — a systematic means to an unlimited integration of cognitive data.

A concept substitutes one symbol (one word) for the enormity of the perceptual aggregate of the concretes it subsumes. In order to perform its unit-reducing function, the symbol has to become automatized in a man’s consciousness, i.e., the enormous sum of its referents must be instantly (implicitly) available to his conscious mind whenever he uses that concept, without the need of perceptual visualization or mental summarizing — in the same manner as the concept “5” does not require that he visualize five sticks every time he uses it.

For example, if a man has fully grasped the concept “justice,” he does not need to recite to himself a long treatise on its meaning, while he listens to the evidence in a court case. The mere sentence “I must be just” holds that meaning in his mind automatically, and leaves his conscious attention free to grasp the evidence and to evaluate it according to a complex set of principles. (And, in case of doubt, the conscious recall of the precise meaning of “justice” provides him with the guidelines he needs.)

It is the principle of unit-economy that necessitates the definition of concepts in terms of essential characteristics. If, when in doubt, a man recalls a concept’s definition, the essential characteristic(s) will give him an instantaneous grasp of the concept’s meaning, i.e., of the nature of its referents.

“The Cognitive Role of Concepts”
Introduction to Objectivist Epistemology, 64-65
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