The Kybalion is a book published in 1908 that outlines the principles of Hermeticism, a philosophical and spiritual tradition based on the teachings attributed to Hermes Trismegistus. It presents seven fundamental laws that govern the universe, including the principles of Mentalism, Correspondence, and Vibration. The authors, who wrote under the pseudonym the "Three Initiates," aim to make these ancient teachings accessible to a modern audience. The book emphasizes the importance of understanding these principles for personal development and mastery over one's life and circumstances.