Mercurial Intelligence designates a mode of knowing associated with the god Mercury-Hermes — rapid, multiform, rhetorically agile, and irreducibly psychological in orientation. The depth-psychology corpus approaches this concept from three overlapping registers. First, the Ficinian-Renaissance register, explored at length by Thomas Moore, characterises Mercurial intelligence as a consciousness in which form, image, and eloquence are epistemologically primary: the shape a thing assumes in imagination discloses its meaning, and the mind is sharpened or dulled through Mercury’s power to shift psychic register. Here the contrast with Minerva’s discursive intellect and Saturn’s fixity is diagnostic. Second, Jung’s alchemical writings situate Mercurius as a figure of transformative and self-generating intelligence — simultaneously the revelatory light of nature and hell-fire, mediating opposites and circling back upon himself in uroboric self-knowledge. In this register, Mercurial intelligence is not a cognitive faculty but a psychic dynamism linking unconscious depth to conscious illumination. Third, James Hillman’s archetypal perspective reads the Hermetic as constitutively different from heroic, solar consciousness: tricky, nocturnal, and generative precisely through its obliquity. Tension persists across the corpus between valuing Mercurial intelligence as a soul-quickening capacity and treating it as a dangerously unmoored function when severed from other planetary or psychic constraints.