Tau (Τ τ) is the twenty-second and final letter of the Greek alphabet, derived from the Phoenician taw, meaning 'mark' or 'sign.' Its numeric value is 300, and its name is cognate with the Hebrew letter Tav (ת), which shares the same symbolic domain: completion, the seal, and the cross. In the Greek magical papyri and later Hermetic traditions, Tau is the letter of the boundary, the threshold, and the synthesis of opposites.

Position on the Tree of Life

Tau is assigned to the 32nd Path of the Tree of Life, the final path connecting Malkuth (the Kingdom) to Yesod (the Foundation). This path is known as the 'Intelligence of the Administration of the House' in the Sepher Yetzirah, governing the materialization of spiritual forces. As the last letter of the alphabet, Tau seals the sequence of paths, representing the gate through which the divine enters the physical world and through which the initiate returns to the source.

Astrological and planetary correspondence

Tau corresponds to the planet Saturn (Shabbathai in Hebrew), the outermost visible planet and the traditional ruler of limitation, time, and structure. In astrological magic, Saturn is the sphere of crystallization and the alchemical nigredo—the blackening that precedes the Great Work. The letter's association with the cross (the crux ansata or tau cross) reinforces its role as the anchor of form and the instrument of sacrifice.

Historical context

The use of Tau as a symbol of completion and salvation predates Greek philosophy. In the Hebrew Bible, the tav was the mark placed on the foreheads of the righteous in Ezekiel 9:4, a sign of preservation. The early Christian adoption of the tau cross as a symbol of Christ's crucifixion (the signum tau) merged with the Greek letter's role as the final letter, signifying the telos—the end and purpose of all things.

In the Greek magical tradition, Tau appears in the Greek Magical Papyri (PGM) as a letter of binding and sealing. The PGM IV 3007-86 describes a ritual using the 'Tau-shaped' lamp to invoke Hekate, the goddess of the crossroads. By the Renaissance, Agrippa von Nettesheim in De Occulta Philosophia (1533) assigned Tau to the 'Intelligence of the Moon' in the Sephirotic system, but later Hermetic Kabbalists such as Athanasius Kircher and the Hermetic Order of the Golden Dawn fixed its correspondence to Saturn and the 32nd Path.

Aleister Crowley, in Liber 777, places Tau at the 32nd Path, linking it to the Saturnian formula of 'Solve et Coagula'—dissolution and coagulation. The letter's shape, resembling the cross, is also the alchemical symbol for the lapis philosophorum (the Philosopher's Stone) in its final, fixed state. In the Book of Thoth Tarot, Tau corresponds to the Universe (or the World) card, which depicts the completion of the Great Work.

In Liber 777

In the table of Liber 777, Tau (Τ τ) appears at the 32nd Path, column LIII (The Greek Alphabet). Its sibling correspondences across the Tree include the letter Sigma (σ) at Chokmah, Epsilon (ε) at Chesed, and Omega (ω) at Tiphereth, but Tau alone governs the final, Saturnian gate. The letter is the seal of the alphabet, the key to the Abyss, and the signature of the completed cosmos.