Buddhism was an Earth religion that originated in the first millennium BC in ancient India. Like many other religions, it was based on a distinction between mind and matter, between an individual consciousness and its physical form. Reincarnation was viewed as an infelicity to be avoided. Buddhism later spread to China, Tibet and Japan, with significant adaptations to each regional cultural tradition.
In Tibet, the idea developed that the consciousness of a lama (teacher) might voluntarily be born again into fleshly existence in order to impart further wisdom to his students and generally to better the conditions of the material world.
While visiting Earth during the mid-22nd century, Doctor Phlox attempted to familiarize himself with the planet's religions. He spent two weeks at a Tibetan Buddhist monastery learning to sing a trichord (triad). (ENT: "Cold Front")