How does the author use symbolism in the book, The Unnamable?

Halley's comet can be regarded as a symbol for the narrator's urge to have a shaped and structured sense of his own identity. Caught in a web of uncertainty and indeterminacy, and within a language that disallows truth, the narrator longs for a trace of an originating self. Since Halley's comet occurs once every 75 years, and flashes by only for a short period of time, it is likely that not every person will experience it. In this sense, the narrator suggests that he may never find this trace.