The Lost Keys of Freemasonry is a study by Manly P. Hall which provides an esoteric insight to Freemasonry. In symbolic way it deals with the basic ideas of the craft as reflected into the three degrees. Freemasonry is presented as the last surviving source of the true secrets and Hall explains the meanings of its rituals. The Lost Keys of Freemasonry are simply the real integration and enactment of Freemasonry principles by "true Masons."