What is the significance of the biblical and supernatural allusions that appear throughout the play?

Troy's brother Gabriel is a symbol of the personal apocalypse of Troy Maxson. Apocalypse, in its original meaning, connotes a revelation, or an understanding of the world that brings about some kind of ending. In Fences, Troy's struggles with his family and with his sense of purpose reveal to him the nature of death and the impermanence of his own life. Gabriel, thinking that he is the literal angel Gabriel, foretells this revelation in Troy's life. He insists that Troy's life is written in St. Peter's book, though his mortality is not a concept of which Troy can conceive. The tragedies of Troy's life serve as a series of death events; the abandonment by his father, his own abandonment of his son, the death of his lover, and ultimately the end of his own life all remind Troy that he is not in control of his own life, even as he attempts to control everyone around him.