Jacob Boehme wrote in The Three Principles of the Divine Essence:
"Behold, there are especially three Things in the Originality, out of which all Things are both, Spirit and Life, Motion and Comprehensibility, viz. SULPHUR, MERCURIUS and SAL."1
Again, Boehme addresses the principles in the Clavis:
"The wise Heathen have in some measure understood this ground, for they say, that in SULPHUR, MERCURY and SAL, all things in this world consist; wherein they have not looked upon the Matter only, but upon the Spirit, from which such Matter proceeds: for the ground of it consists not in salt, quicksilver and brimstone, they mean not so, but they mean the Spirit of such properties; in that every thing indeed consists, whatsoever lives and grows, and has a being in this world, whether it be spiritual or material."2
Much has been addressed concerning one or the other of Three Principles in Man and Nature in this site. Yet volumes more may be written. Boehme may be difficult reading for the beginning miner, but do not give him up. In alchemy it is good to stretch our reading to the limits of comprehension. Subconsciousness (de Balneo) will churn the information for a period before she lets glints of comprehension surface. After a period reread the matter and be amazed by what comes into Light. But, why are there Three Principles?
In geometry three points determine a plane, rendering an even, flat surface plane for sure foundations. So is it with the spiritual principles. Keep ever in mind the sagely advice of Roger Bacon and countless other alchemists and mystics that all the philosophers speak of ONE THING. However, there are three major aspects or modes to this ONE, TRIUNE-GOD. All the major faiths and countless minor theologies from all times and climes agree to this triumvirate in one essence.
Alchemical writings constantly tender references to Universal Mercury, Sulphur and Salt. Never are these intended as the tangible substances, but rather qualities of an intangible, divine quintessence. The three modes lie within ONE. Never can any one of these be considered isolated of the other two. Each may act predominantly over the others being latent, however. In all manifestations appraised lifeless, these three living substances lay occult. While the object may appear dead, intelligence and animation are merely in a somnolence, latency. The mysterious potency of Mercury and Sulphur are smothered under the preponderance of Salt, and may be tapped by an Adept who personifies the fullest expression of the Almighty. Everything in creation, visible or invisible, is the Living Mind-Matter of God, Almighty. That each of us will eventually come to this reality is a certainty. It has been built into Its own Essence since the no-beginning. Some of the world's triumvirates are tabled here.
Ain Suph Aur, or Mulaprakiti, or Prima Materia breaks out, develops or manifests into three modes or expressions:
Kether Chokmah Binah
Crown Wisdom Understanding
Omniscience Omnipotence Omnipresence
Spirit Soul Body
Brahma Shiva Vishnu
Sattvaguna Rajasguna Tamasguna
Mercury Sulphur Salt
Father Son Holy Spirit
Osiris Horus Isis
Air Fire Water
Purusha Prana Akasha
Intelligence Desire Embodiment
Being Life-Force Substance
Essence Animation Matter
Super-cons Self-cons Sub-cons
Androgynous Masculine Feminine
The list could continue endlessly from around the world. It matters not how we classify, or what vocabulary we choose. Please do not be too hasty with disagreement toward the attributions of Horus and the Son to the second sphere, Chokmah, on the Tree of Life. Consider their Source. While it is true that Chokmah is named AB, Father, and Tiphareth is called BN, the Son, and both Horus and the Son of Man are often attributed to the sixth sphere, Beauty. We must consider that the Father and the Son are ONE, in absolute union; that ABN (AB and BN) is Hebrew for Stone. The partial list above is the Supernal Universal Triumvirate before any manifestation whatever. The Son or Horus, in this sense, is the drive behind and prior to all creation, before any tangible substance anywhere. The separation and involution of this drive is what manifests in the visible planes as the Christ Consciousness, Tiphareth, at full self-conscious attainment. Horus, or Son, evolves the full potency of the Father in matter. The reunion once again brings Father and Son into Oneness, ABN, the Stone.
As supplemental research may I suggest referring to the Fourteenth Chapter in the Bhagavad-Gita titled The Three Modes of Material Nature. It doesn’t matter which version or from which author. The chapter clearly describes these three aspects as manifest through the human personality. The descriptions of the three Gunas are in exact agreement with what the sagely alchemists labeled Mercury, Sulfur and Salt.
1 Boehme, Jacob, Three Principles Of The Divine Essence. Chicago: Yogi Publication Society, 1909, pg. 15.
2 Boehme, Jacob, Clavis. Trans. by William Law. Grand Rapids, MI: Phanes Press, 1991, pg. 46.