The most tangible of all visible mysteries - fire.

Hunt’s aphorism treats fire as a paradox: it is plainly visible and physically real—warmth, light, flame—yet it remains elusive in substance and behavior. Unlike solid objects, fire cannot be grasped or held; it is a process (combustion) that continually changes shape, consumes fuel, and vanishes when conditions fail. Calling it the “most tangible” mystery highlights how it can be directly experienced by the senses while still resisting ordinary categories of matter. The line also resonates with Romantic-era fascination with elemental forces as symbols of vitality, imagination, and transformation—something at once intimate (hearth, candle) and uncanny (conflagration).