The concept of 'purgatory' is in Catholic Church dogma, and most black people are not Catholic - mostly their Christian realities focus on heaven or hell. Purgatory is for the expiation of sin, the fact that you are there, and not in hell, means you'll eventually work your way to heaven. The experience of this play, 'Small oak tree', and its psychological architecture, relies on its knowledge of that. Many black people believe that this life, within itself, is a way to work out whatever obligations we have, in order to get to a better place.