What is plato’s symbol for true enlightenment in "the allegory of the cave."

Which line in this excerpt from "the love song of j. alfred prufrock" by t.s. eliot uses synecdoche? shall i say, i have gone at dusk through narrow streets and watched the smoke that rises from the pipes of lonely men in shirt-sleeves, leaning out of windows? i should have been a pair of ragged claws scuttling across the floors of silent seas.