Robert Collier (1885-1950) was an American author of self-help and New Thought metaphysical books in the 20th century. Collier's writings, including the multi-volume 'The Secret of the Ages' (1926), focused on harnessing the power of the mind, spiritual psychology, and self-improvement. He is most famous for his book 'The Secret Power Within You,' which is often contained within the 'Robert Collier Boxed Set', a compilation that encompasses his views on the power of personal belief and the role of the subconscious in shaping one's reality. Collier's literary style integrates motivational discourse with practical advice, aiming to provide readers with the methods to tap into their inner potential and achieve success in various aspects of their lives. His work, which encourages readers to utilize the law of attraction and positive mental visualization, has been cited as influential in the area of personal development literature and has continued to be popular among enthusiasts of success psychology. Collier's enduring legacy resides in the principles that one's thoughts can significantly influence one's personal experience—a theme that precursor to many contemporary motivational writers.