At the beginning of A Portrait of the Artist as a Young Man, James Joyce makes use of the Roman poet Ovid's Metamorphoses, which contains the legend of Dædalus and Icarus; this reference provides a foreshadowing of and a structure for Joyce's semi-autobiographical novel. (You should notice immediately that the protagonist in Portrait is named Stephen Dedalus.)
In the myth, the father, Dædalus, fashions wings for himself and his son, Icarus, so they can fly to freedom from their imprisonment in the Labyrinth. The father warns Icarus to avoid flying too high; the heat of the sun will melt the wax holding the feathers on the wings. However, astonished and fascinated by the flight, Icarus does indeed fly too high, and the father watches in torment as his son falls into the sea.
Joyce's main character, Stephen Dedalus, grows through the stages of his life, at times amazed by the “truth” of it and fascinated by the experiences that lead him to higher levels of understanding and inspiration. One thing he says he has always known about himself is that he is “different from others.” As he “soars” into uncharted areas, he is unafraid of exploring every circumstance that presents itself. Stephen questions the religion, restrictive sexuality, customs, politics, and philosophy of his upbringing and of Ireland in order to be true to his perceptions of himself as an artist of his own making.
Rather than writing a conventionally organized novel that moves chronologically and transitions from one occurrence smoothly into another, however, Joyce depicts Stephen's Dedalus' life through events that are significant in their own right. All moments are important in and of themselves, but they are more important because they echo the past and foreshadow the future. The narrator's use of vocabulary, diction, and sentence structure reflects Stephen's growth and maturity. Note the immaturity of the writing in the first chapter and how it contrasts but also complements Joyce's language and themes in later chapters.
Much of the literary importance of Portrait stems from Joyce's use of moments that evoke an epiphany. In common usage, an epiphany indicates a sudden moment of realization or understanding that comes from an intense experience. Stephen's epiphanies, however, occur during everyday life. For example, Stephen realizes that beauty can be appreciated for its own self and decides to become a writer simply by seeing a woman wading at the beach. In addition, they build on and refer to one another throughout the novel.
Joyce uses stream-of-consciousness less frequently in Portrait than in his later novels, Ulysses and Finnegan's Wake, but the technique is present here. As an example, when he is writing from the perspective of a child, Stephen's perceptions, thoughts, and understandings are jumbled and disjointed. As Joyce allows Stephen to grow, the technique is employed to approximate human thinking, through digressions and interrupting thoughts. By the final chapter, however, Stephen's vocabulary is sharp, sophisticated, and precise, as is his philosophy and belief in his talents.