In order fully to grasp a concept as a single unit, the human mind needs to concretize it by means of a symbol. Consequently, we associate our concepts with the words of language—including not only nouns, but other parts of speech as well.

It is frequently asserted that language's primary purpose is communication. A little reflection, however, reveals that while communication is certainly important, language's primary purpose must be cognition. First, a human cannot communicate until his or her mind has first grasped something to communicate, so that cognition itself must take precedence over communication. Without any conceptual grasp of reality, animals can communicate only in grunts and other noises associated with a perceptual consciousness—and such communications do not constitute what linguists and others call "language." Furthermore, when deprived of a system of linguistic symbols, human conceptual cognitive abilities are severely limited. Hearing-impaired persons not diagnosed at an early age, for instance, do not acquire exposure to language and consequently exhibit impaired conceptual development, at least temporarily. If they are then diagnosed and taught sign language, however, they can gradually close this cognitive gap.