The furnace in the depth-psychological corpus occupies a position that is simultaneously technical, symbolic, and transformative — functioning as the primary container and director of alchemical heat and, by analogical extension, as a figure for psychic intensification. Hillman offers the most sustained typological analysis, cataloguing ascending, descending, sand, reverberating, blasting, and bladder furnaces as distinct psychic modalities, each governing a specific quality of inner work. Abraham establishes the furnace’s theological dimension through the Sophic Hydrolith’s ‘furnace of affliction,’ wherein base humanity is purified into spiritual illumination — a reading that connects directly to Edinger’s powerful exegesis of Nebuchadnezzar’s fiery furnace as the archetypal site of calcinatio, where inflated ego authority meets transpersonal resistance and the totality of the Self emerges as a fourth figure. Jung’s appropriation of Pordage frames the furnace as ‘sacred’ matrix — identified with the balneum Mariae, the womb, and the source of the divine Tincture — yoking it to the love-fire of Venus rather than the destructive fire of Mars. The Paracelsian tradition, as recovered by Jung in the Alchemical Studies, further internalizes the furnace: while the artifex heats substance in the furnace, he undergoes an identical moral purification. Across these voices, the furnace is the indispensable locus where desire is disciplined, matter is transformed, and the self is remade.