Zen is not a school or sect of Buddhism

Learned audience, you should remember that Zen is not a school or sect of Buddhism, Zen is the authentic transmission of Buddhism itself. It is not my intention to delve into the history of Buddhism or Zen; I only remind you that Zen did not suddenly spring, full-blown, out of the ground. Zen is the natural evolution of a living, dynamic reality. As soon as we try to define it we stop it in its tracks and murder it.

The Flatbed Sutra of Louie Wing