Charles F. Haanel was an American businessman and New Thought author born in Michigan in 1866. After building a successful career in commerce, he turned his attention to writing about concentration, mental discipline, visualization, and the relationship between thought and outward achievement.Haanel's most influential work, The Master Key System, was originally issued as a correspondence course consisting of twenty-four lessons. Its systematic approach to mental training, self-mastery, and purposeful thought made it a lasting influence on later motivational and personal-development writers.