The term 'Single-Principle Philosopher' refers to a Monist, which is a person who believes that all of reality is based on a single principle. This philosophical belief is often associated with the idea that all of reality is interconnected and that everything is part of a unified whole. Monism is an ancient philosophical concept that has been around since the time of the ancient Greeks. It has been adopted by various religious and spiritual traditions, including Buddhism, Hinduism, and Taoism.