"The Science of Being Great" is from the author Wallace D. Wattles (1860 - 1911), whose work inspired the cult-phenomenon book and film "The Secret". He was a widely popular and pioneering writer in the self-help and success genres. According to Wattles each person has within themselves a Principle of Health. (The word Principle is used as meaning source.) The Principle of Health in a person, when in full constructive activity, causes all the voluntary functions of his life to be perfectly performed. It is the Principle of Health in a person which really works all healing, no matter what system.