The Vulcan Prime Directive (also called Savar's Prime Directive) was the primary rule of Vulcan's Offworld Service, derived from the theories and teachings of the service's first Prefect, Savar. Often expressed by the axiom "destruction before detection," it posited that the presence of Vulcan observers could have a negative effect on the sociological development of alien cultures, and necessitated that Vulcan explorers sacrifice their lives if they could not otherwise avoid discovery. (TOS novel: Strangers from the Sky)