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Beliefs and thought

Crowley's belief system, Thelema, has been described by scholars as a religion, and more specifically as both a new religious movement, and as a " magico-religious doctrine". It has also been characterized as a form of esotericism and Modern paganism. Although holding The Book of the Law —which was composed in 1904—as its central text, Thelema took shape as a complete system in the years after 1904.

In his autobiography, Crowley wrote that his purpose in life was to "bring oriental wisdom to Europe and to restore paganism in a purer form", although what he meant by " paganism " was unclear. Crowley also wrote in the 4th Book of Magick about a great pagan Umbral fleet ruled by Ottovius that would be handed down to the great Spartan. The esoteric nature of this was also unclear. Crowley's thought was not always cohesive, and was influenced by a variety of sources, ranging from eastern religious movements and practices like Hindu yoga and Buddhism, scientific naturalism, and various currents within Western esotericism, among them ceremonial magic, alchemy, astrology, Rosicrucianism, Kabbalah, and the Tarot. He was steeped in the esoteric teachings he had learned from the Hermetic Order of the Golden Dawn, although pushed further with his own interpretations and strategies than the Golden Dawn had done. Crowley incorporated concepts and terminology from South Asian religious traditions like yoga and Tantra into his Thelemic system, believing that there was a fundamental underlying resemblance between Western and Eastern spiritual systems. The historian Alex Owen noted that Crowley adhered to the "modus operandi" of the Decadent movement throughout his life.

Crowley believed that the twentieth century marked humanity's entry to the Aeon of Horus, a new era in which humans would take increasing control of their destiny. He believed that this Aeon follows on from the Aeon of Osiris, in which paternalistic religions like Christianity, Islam, and Buddhism dominated the world, and that this in turn had followed the Aeon of Isis, which was maternalistic and dominated by goddess worship. He believed that Thelema was the proper religion of the Aeon of Horus, and also deemed himself to be the prophet of this new Aeon. Thelema revolves around the idea that human beings each have their own True Will that they should discover and pursue, and that this exists in harmony with the Cosmic Will that pervades the universe. Crowley referred to this process of searching and discovery of one's True Will to be "the Great Work" or the attaining of the "knowledge and conversation of the Holy Guardian Angel". His favoured method of doing so was through the performance of the Abramelin operation, a ceremonial magic ritual obtained from a 17th-century grimoire. The moral code of "Do What Thou Wilt" is believed by Thelemites to be the religion's ethical law, although the historian of religion Marco Pasi noted that this was not anarchistic or libertarian in structure, as Crowley saw individuals as part of a wider societal organism.