Tiphareth, Beauty or harmony, is the sixth sefirah and the heart of the Tree of Life, positioned at the centre of the whole figure where the influences of the sefirot above and below, and of the pillars of mercy and severity on either side, are gathered and reconciled. It is the sphere of balance, of the reconciling son who mediates between the supernals and the lower world, and it is traditionally associated with the Sun, sacrificial kingship and the harmonising centre that holds the opposites in equilibrium. More paths meet at Tiphareth than at any other sefirah, marking it as the great point of mediation. Its divine name is YHVH Eloah va-Daath, God made manifest in the sphere of mind.
In the Kabbalistic understanding Tiphareth is the seat of harmony and compassion, the beauty that arises when mercy and severity are perfectly balanced, and it stands directly below Kether on the central Pillar of Equilibrium, reflecting the crown into the created world. The sefirah belongs to the doctrine named in the Sefer Yetzirah and developed through the Zohar and the later Kabbalah.
Sources The ZoharTraditionally attributed to Moses de Leon with Sefer Yetzirah: The Book of Creation in Theory and PracticeAryeh Kaplan