An epiphany is a sudden, unpremeditated insight into the essential meaning of an object. The observer perceives in a whole new way extraordinary beauty and unity in an otherwise ordinary thing. When such an experience appears in a work of literature, the artist presents it in a symbolic way.
It is his aesthetic belief which prompts Joyce to use the technique of epiphany in his written work, particularly in The Portrait of the Artist as a Young Man. Joyce believed that it was the obligation of an author to record these fleeting moments of metaphysical beauty. In Stephen Hero, the first draft of the novel, Stephen explains the occurence of it thus: Its soul, its whatness, leaps to us from the vestment of its appearance. The soul of the commonest object...seems to us radiant. The object achieves its epiphany."
Epiphanies in the novel include Stephen's otherworldly perception of the young girl wading "in midstream, alone and still, gazing out to sea...like one whom magic had changed into the likeness of a strange and beautiful sea creature," and the swallows seen from the steps of the library.