As far as thought is concerned, and at all-levels of thought, it [mental life] is a symbolic process. It is mental not because the symbols are immaterial, for they are often material, perhaps always material, but because they are symbols. . . . The essential act of thought is symbolization. — A. D. Ritchie, The Natural History of the Mind
Symbolization is the essential act of mind
Not higher sensitivity, not longer memory or even quicker association sets man so far above other animals that he can regard them as denizens of a lower world: no, it is the power of using symbols—the power of speech—that makes him lord of the earth. So our interest in the mind has shifted more and more from the acquisition of experience, the domain of sense, to the uses of sense-data, the realm of conception and expression. The importance of symbol-using, once admitted, soon becomes paramount in the study of intelligence. . . . Symbolism is the recognized key to that mental life which is characteristically human and above the level of sheer animality. Symbol and meaning make man’s world, far more than sensation; Miss Helen Keller, bereft of sight and hearing, or even a person like the late Laura Bridgman, with the single sense of touch, is capable of living in a wider and richer World than a dog or an ape with all his senses alert. [33, 35]
The symbol-making function is one of man’s primary activities, like eating, looking, or moving about. It is the fundamental process of his mind, and goes on all the time. Sometimes we are aware of it, sometimes we merely find its results, and realize that certain experiences have passed through our brains and have been digested there. . . . Symbolization is the essential act of mind and mind takes in more than what is commonly called thought. [44-45]
Sign vs. Symbol
Because a sign may mean so many things, we are very apt to misinterpret it, especially when it is artificial. Bell signals, of course, may be either wrongly associated with their objects, or the sound of one bell may actually be confused with that of another. But natural signs, too, may be misunderstood. Wet streets are not a reliable sign of recent rain if the sprinkler wagon has passed by. The misinterpretation of signs is the simplest form of mistake. It is the most important form, for purposes of practical life, and the easiest to detect; for its normal manifestation is the experience called disappointment. . . .
A term which is used symbolically and not signally [i.e. as a “sign” for something else] does not evoke action appropriate to the presence of its object. If I say: “Napoleon,” you do not bow to the conqueror of Europe as thoughI had introduced him, but merely think of him. If I mention a Mr. Smith of our common acquaintance, you may be led to tell me something about him “behind his back,” which is just what you would not do in his presence. Thus the symbol for Mr. Smith—his name—may very well initiate an act appropriate peculiarly to his absence. Raised eyebrows and a look at the door, interpreted as a sign that he is coming, would stop you in the midst of your narrative; that action would be directed toward Mr. Smith in person.
Symbols are not proxy for their objects, but are vehicles for the conception of objects. To conceive a thing or a situation is not the same thing as to “react toward it” overtly, or to be aware of its presence. In talking about things we have conceptions of them, not the things themselves; and it is the conceptions, not the things, that symbols directly “mean.” 'Behavior toward conceptions is what words normally evoice; this is the typical process of thinking. Of course a word may be used as a sign, but that is not its primary role. Its signific character has to be indicated by some special modification—by a tone of voice, a gesture (such as pointing or staring), or the location of a placard bearing the word. In itself it is a symbol, associated with a conception, not directly with a public object or event. The fundamental difference between signs and symbols is this difference of association, and consequently of their use by the third party to the meaning function, the subject; signs announce their objects to him, whereas symbols lead him to conceive their objects. The fact that the same item—say, the little mouthy noise we call a “word”—may serve in either capacity, does not obliterate the cardinal distinction between the two functions it may assume. 
Langer, Suzanne K. Philosophy in a New Key: A Study in the Symbolism of Reason, Rite, and Art (1941). New York: Mentor/American Library, 1951.
Last modified 14 July 2019