Robert Collier Robert Collier was an American author and publisher whose writings on mental power, prosperity, faith, and success became widely read in the early twentieth century. Best known for The Secret of the Ages and The Robert Collier Letter Book, Collier wrte in the tradition of New Thought and success literature, combining practical ambition with the belief that thought, imagination, and conviction influence opportunity and achievement. His work remains important to readers interested in prosperity philosophy, positive thinking, and the roots of modern motivational writing. Read More Read Less