Metempsychosis

Metempsychosis was the philosophical belief in the transmigration of the soul, also known as reincarnation. (PROSE: Empire of Death) It was a belief present in ancient Egypt and Greece. Pythagoras was a metempsychologist, and was tutored in its philosophy by Oenuphis in Egypt.

Pythagoras believed that the Doctor's regenerations were living proof of metempsychosis. (PROSE: The Pythagoras Problem)