Send us a text Who was Charles Haanel? Charles Francis Haanel (1866–1949) was an American author, businessman, and philosopher best known for writing The Master Key System in 1912. He was a successful entrepreneur who applied the same principles of discipline, visualization, and mental focus in his own business life that he later codified in his book. Haanel believed that the human mind had untapped power, and by training thought and intention, a person could influence their reality. The Impo...