A plane is not necessarily a planet. A plane may be one planet, but a plane may also exist where no planet is. One planet may have several planes. Planes may also involve various aspects of apparent time. Planes can and do intermix without the knowledge of the inhabitants. A plane may be a time... or only one iota of vitality that exists all by itself. A plane may cease to be. A plane is formed for entities as patterns for fulfillment along various lines. It is a climate conducive to the development of unique and particular capabilities and achievements... an isolation of elements.

p. 103-104 - Seth, Dreams & Projections of Consciousness, (1986)