The novel begins with Stephen Dedalus' first memories, when he was about three years old. The fragmented lines are from a childhood story and a nursery song, and are linked with family associations, sensory perceptions, and pieces of conversation. In this opening scene, Joyce is presenting to us the genesis of a future artist's perception and interpretation of the world.
Moving from Stephen's infancy to his early days at Clongowes Wood College, a Jesuit boarding school for boys, Joyce focuses on three key incidents which significantly affect Stephen's personality. First, Stephen is pushed into an open cesspool by a bullying classmate, and, subsequently, he develops a fever which confines him to the school infirmary; here, he begins to discern that he is "different," that he is an outsider.
Later, when he is probably six years old, Stephen returns home to celebrate Christmas dinner with his family and is invited, for the first time, to sit with the adults at the dinner table. This extraordinarily happy occasion is marred by a heated political argument between Stephen's old nurse, Dante Riordan, and a dinner guest, Mr. Casey, leaving Stephen confused about the issues of religion and politics in the adult world.
On returning to school, Stephen accidentally breaks his glasses and is unable to complete his classwork. He is unjustly humiliated and punished by the cruel prefect of studies, but after receiving encouragement from a friend, Stephen bravely (if fearfully) goes to the rector of the school and obtains justice. The success of this meeting instills in him a healthy self-confidence and ennobles him, for a moment, in the eyes of his classmates.
After a brief summer vacation at his home in Blackrock, Stephen learns that his father's financial reversals make it impossible to return to Clongowes Wood; instead, he is enrolled in a less prestigious Jesuit day school, Belvedere College. Here, he develops a distinguished reputation as an award-winning essay writer and a fine actor in his school play. Despite these accomplishments, however, Stephen feels increasingly alienated from his schoolmates because of his growing religious skepticism and his deep interest in literature and writing. This feeling of isolation is intensified during a trip with his father to Cork, where he learns more about his father's weaknesses.
Stephen becomes increasingly repelled by the dead-end realities of Dublin life. Frustrated by his loss of faith in the Catholic Church, in his family situation, and in his cultural bonds, Stephen seeks to "appease the fierce longings of his heart." After wandering through the city's brothel district, he finds momentary solace with a Dublin prostitute. He is fourteen years old, and this is his first sexual experience.
After a period of "sinful living," Stephen attends an intense three-day spiritual retreat. During that time, he is overwhelmed by guilt and remorse; he believes that Father Arnall is speaking directly to him. Panicking, he seeks out a kindly old Capuchin priest, pledges moral reform, and rededicates himself to a life of purity and devotion. He fills his days with fervent prayers and takes part in as many religious services as he can.
Noticing Stephen's exceedingly pious behavior, the director of the school arranges a meeting to encourage Stephen to consider entering the priesthood. At first, Stephen is flattered, fascinated by the possibilities of the clerical life, but increasingly he is tormented by carnal desires. He finally realizes that his "inherent sinful nature" makes it necessary for him to reject a religious vocation.
Having made this discovery about himself, Stephen decides to enroll in the university, where he hopes to shape his destiny as an artist. This decision is immediately followed by a climactic "epiphany": he sees a girl wading in the sea; to Stephen, she embodies the attraction, the promise, and the abandon which he wishes to experience in life. It is at this moment that Stephen understands that he can only hope to gain this experience through a life of artistic expression.
Shortly thereafter, Stephen begins a new life as a young man in search of his own values and his own credo. In comparison with the other college students, Stephen often seems anti-social and more concerned with pursuing his own interests than supporting the causes of others. Even Stephen himself realizes that unlike most of his friends, he is unusually introspective. He is not the typical devil-may-care university student; he rejects the typical blind patriotic blather, and although he continues to respect the Catholic faith, he no longer believes that its tenets should govern his life. Through conversations with friends and a dean of studies, Stephen eventually develops his own aesthetic theory of art, based on the philosophies of Aristotle and Aquinas. Simultaneously, he concludes that if he is ever going to find his artistic soul, he must sever all bonds of faith, family, and country. He must leave Dublin and go abroad to "forge" his soul's "uncreated conscience."