In Sleep
Dream logic
The parenthetical insists this is a real dream, not a metaphor. Meynell is reporting something that actually happened in sleep—important because the ending depends on dream physics.
Victorian atheism
This is the standard Victorian doubt speech—social suffering as proof against God. But notice he's crying while he says it.
Who invented compassion
The logic trap: if there's no God, where did the atheist's compassion for the poor come from? Meynell's answer: God is the source of the very pity used to argue against Him.
Mirror reversal
Christ sees Himself reflected in the atheist's compassionate tears. The man's pity for the poor is God's own pity looking back at Him.