The higher organisms possess a much more potent form of consciousness: they possess the faculty of retaining sensations, which is the faculty of perception. A “perception” is a group of sensations automatically retained and integrated by the brain of a living organism, which gives it the ability to be aware, not of single stimuli, but of entities, of things. An animal is guided, not merely by immediate sensations, but by percepts. Its actions are not single, discrete responses to single, separate stimuli, but are directed by an integrated awareness of the perceptual reality confronting it. It is able to grasp the perceptual concretes immediately present and it is able to form automatic perceptual associations, but it can go no further.
Man’s senses are his only direct cognitive contact with reality and, therefore, his only source of information. Without sensory evidence, there can be no concepts; without concepts, there can be no language; without language, there can be no knowledge and no science.
Although, chronologically, man’s consciousness develops in three stages: the stage of sensations, the perceptual, the conceptual—epistemologically, the base of all of man’s knowledge is the perceptual stage.
Sensations, as such, are not retained in man’s memory, nor is man able to experience a pure isolated sensation. As far as can be ascertained, an infant’s sensory experience is an undifferentiated chaos. Discriminated awareness begins on the level of percepts.
A percept is a group of sensations automatically retained and integrated by the brain of a living organism. It is in the form of percepts that man grasps the evidence of his senses and apprehends reality. When we speak of “direct perception” or “direct awareness,” we mean the perceptual level. Percepts, not sensations, are the given, the self-evident. The knowledge of sensations as components of percepts is not direct, it is acquired by man much later: it is a scientific, conceptual discovery.
[Man’s] senses do not provide him with automatic knowledge in separate snatches independent of context, but only with the material of knowledge, which his mind must learn to integrate. . . . His senses cannot deceive him, . . . physical objects cannot act without causes, . . . his organs of perception are physical and have no volition, no power to invent or to distort . . . the evidence they give him is an absolute, but his mind must learn to understand it, his mind must discover the nature, the causes, the full context of his sensory material, his mind must identify the things that he perceives.
Let the witch doctor who does not choose to accept the validity of sensory perception, try to prove it without using the data he obtained by sensory perception.
The arguments of those who attack the senses are merely variants of the fallacy of the “stolen concept.”
As far as can be ascertained, the perceptual level of a child’s awareness is similar to the awareness of the higher animals: the higher animals are able to perceive entities, motions, attributes, and certain numbers of entities. But what an animal cannot perform is the process of abstraction—of mentally separating attributes, motions or numbers from entities. It has been said that an animal can perceive two oranges or two potatoes, but cannot grasp the concept “two.”
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.