What other dungeon is so dark as one’s own heart! What jailer so inexorable as one’s self!

The quote suggests that the most oppressive confinement is not a physical prison but the inner life: one’s own heart can become a “dungeon” when filled with fear, shame, or unresolved guilt. The “jailer” is the self—conscience, self-reproach, and the mind’s capacity to rehearse accusations without mercy. Hawthorne’s phrasing implies that external punishment may be finite or escapable, but internal condemnation can be relentless and self-renewing. The line also critiques moral absolutism turned inward: when a person becomes judge and executioner of their own worth, they can create a private tyranny more severe than any imposed from outside.