The Master Key System is a self help book by American author and philosopher Charles F. Haanel, first published in 1916. It was originally published as a 24 week correspondence course in 1912 and contains many new thought concepts such as the law of attraction, and creative visualisation. Each chapter contains a section to read, an exercise towards the end, followed by a section with questions and answers. It has had a huge influence on successive New Thought writers, particularly those preaching 'Prosperity Consciousness.' The 'Law of Attraction' is at the heart of Haanel's system, but it was also influenced by beliefs such as Hinduism, Freemasonry, Rosicrucianism, Theosophy, and Christianity.