How is epiphany used in A Portrait of the Artist as a Young Man?

In A Portrait of The Artist as A Young Man, James Joyce uses moments of clarity and a recognition of another perspective as "epiphanies." The reader becomes aware of the change in Stephen's character, however momentary, and this drives the plot of the novel. In Stephen Hero, an earlier version of A Portrait of The Artist as a Young Man, Stephen is referring to the clock at the Ballast Office, a seemingly insignificant building and clock but capable of making Stephen think because, "all at once I see it and I know at once what it is: epiphany." 

Stephen will face many challenges and his self-development and sense of awareness will reflect the impact of life and the economic hardships that he and his family must confront. This ensures that "epiphany' is a very personal experience. Having felt "small and weak" throughout the first chapter due to his own shortcomings, Stephen, at the conclusion of chapter one, comes to a realization that he is in a position to embarrass Father Dolan but, in a schoolboy version of humility, despite being justified in bringing Father Dolan to account, he vows that he will not.

After his sexual encounter and his epiphany at the end of chapter two; "surrendering himself;" he becomes weighed down by his own sinful acts which "kill(s) the body and (it) kill(s) the soul." By the end of chapter three, he revels in the life-changing potential that he now faces and the power and potential of "Another life! A life of grace and virtue and happiness!" As Stephen takes Communion, he feels the real power of the act of Holy Communion as he accepts that "Past is past." His feelings are very real and immediate, even if by the end of chapter four he chooses one path and then a different path. Life and experience goes "on and on and on and on."

By the end of the novel, Stephen has realized the power of his own contribution, not only to his self-development, but in promoting "the uncreated conscience of my race." James Joyce ensures continuity through the use of  epiphany because all of the revelations and realizations provide Stephen with guidance and acknowledge the contribution of each and every experience in developing Stephen's character and his ability to make a difference.