In alchemy this would mean the rubedo, already referred to in the Senior quotation in the fourth parable: "He shineth in colour like a ruby through the tinctur-ing soul, which it hath acquired by virtue of the fire." °° 'This is the much-prized color invariabilis (unchanging colour), whose origin the Turba attributes to the soul: "For out of sulphur mixed with sulphur cometh the most precious colour, which doth not vary nor flee from the fire, when the soul is introduced to the innermost parts of the body, and containeth and giveth colour to the body." 5+ ""O wonderful nature, which coloureth the other natures, O heavenly natures, which transform . . . the elements!" ®5 This anima tingens is of a spiritual nature °° and assimilates the body to itself so that it too becomes spirit-ual.57 When the body is pulverized to a "spiritual powder" the fire tinges it with the "unchanging colour'; and "this spirit which you seek, that you may tinge somewhat therewith, is hidden and concealed in the body, like unto the soul in a man's body."
— Marie-Louise von Franz
The alchemists were not confused about what they meant by colour. Colour is not decoration, not surface quality — it is the sign that something has been genuinely changed rather than merely covered. The *color invariabilis* is the proof: a redness that does not flee the fire because it was not added from outside but generated from within, sulphur acting on sulphur, the soul already coiled inside the body's own substance. What von Franz is tracing here is the alchemical insistence that spirit does not descend into matter from elsewhere. It rises out of matter's own deepest constitution when that matter is broken open finely enough — pulverized, as the text has it, to a spiritual powder.
Notice where the spirit is said to be hidden: inside the body, like a soul inside a man's body. Not above it, not awaiting it, not arrived from some higher register. The soul is already there, coloring the body from within, and the fire's work is simply to make what was occult visible. This is the claim that troubles every project of ascent, every reading of alchemy as a coded map toward dematerialized unity. The tincturing soul does not carry matter upward; it transforms matter by being found inside it. The ruby is not a departure from the red earth. It is what the earth becomes when it stops fleeing its own heat.
Marie-Louise von Franz·Aurora Consurgens: A Document Attributed to Thomas Aquinas on the Problem of Opposites in Alchemy·1966