Liber AL vel Legis, commonly known as The Book of the Law (1904), is the foundational text of Thelema, the spiritual and philosophical system developed by Aleister Crowley. According to Crowley, the book was dictated to him over three days in Cairo by a non-human intelligence named Aiwass, described as his Holy Guardian Angel. The text is divided into three short chapters, each spoken by a different symbolic voice: Nuit, the infinite goddess of space; Hadit, the point of individual consciousness; and Ra-Hoor-Khuit, a god of force and authority. Together, these voices proclaim the advent of a new spiritual era, the Aeon of Horus, centered on individual will, self-realization, and freedom. The book's central principle is expressed in its most famous line: "Do what thou wilt shall be the whole of the Law." This statement emphasizes the discovery and fulfillment of one's True Will, rather than indulgence or moral chaos. The language is poetic, cryptic, and deliberately challenging, inviting interpretation rather than dogma. Brief yet dense, Liber AL vel Legis blends mysticism, symbolism, and prophecy. Its influence extends across modern occultism, esoteric philosophy, and alternative spirituality, remaining one of the most significant texts of twentieth-century esoteric thought.

Aleister Crowley (1875–1947) was an English occultist, writer, poet, and ceremonial magician. A controversial figure, he founded the spiritual philosophy of Thelema and authored numerous esoteric works. His influence spans modern occultism, ritual magic, mysticism, and countercultural movements of the twentieth century.