*Liber 31* is a mystical diary and doctrinal text by Charles Stansfield Jones (Fr. Achad), written in 1918 within the Thelemic occult tradition founded by Aleister Crowley. It records Jones's account of his initiatory experiences from 1916–1918, in which he claims to have ascended through and beyond the grades of the A∴A∴ magical order — from Master of the Temple (8=3) through Magus (9=2) to Ipsissimus (10=1) — culminating in a mystical dissolution of selfhood into what he calls "the One That Is Not." The central argument is that Jones has discovered a key to the Book of the Law (Liber Legis) through the number 31, which encodes the identity of AL (God) and LA (Not), and that reversing, reflecting, or inverting symbols — particularly the letters of his magical motto Parzival — reveals hidden doctrinal truths about creation, annihilation, and the Kabbalistic Tree of Life. Jones makes the distinctive and audacious claim that he has surpassed his teacher Crowley (referred to as "Therion" or "the Great Magician") on the initiatory path, framing Crowley's denial of this as itself fulfilling a cosmic function in the Thelemic hierarchy. The text is notable for blending personal spiritual autobiography with Kabbalistic numerology, claiming that the mystical experience of "Selflessness IS Self" is the defining secret of the highest grade, and presenting Jones's discovery as a key that unlocks previously unsolved passages in Crowley's sacred text.