This scene restages the cave in Plato's Republic, the famous sequence wherein Plato portrays mankind as seeing shadows of things only, not their true nature. In Plato's view, ascending out of the shadows and into the light reveals the source of the good. Conrad turns that notion on its ear. What is actually casting the shadow here is the dead, tortured body of Hirsch, meaning that in Nostromo, the true nature of "man" is a reality of torture and death. The lighting is consistent with the symbolism of the novel, in which shadows mercifully hide the ugly reality from us, and light becomes a painful disillusionment. Other aspects of the room -- the fire, the smoke, the fact that the light is above -- serve to vividly evoke Plato's famous cave.

The metaphor serves to present the grim truth of perpetual exploitation to the People at the very moment when they are seeking a way to escape that exploitation. The dialogue that follows leads the reluctant People ever closer to the socialist solution.