According to author ralph ellison why do symbols probably appear in literature

 “Symbolism arises out of action…Once a writer is conscious of the implicit symbolism which arises in the course of a narrative, he may take advantage of them and manipulate them consciously as a further resource of his art. Symbols which are imposed upon fiction from the outside tend to leave the reader dissatisfied by making him aware that something extraneous is added.” -Ralph Ellison