 While the Ainur, the first-created but immaterial angelic beings, have the "subcreative" power of imagination, the power to create independent life or physical reality is reserved for Eru Ilúvatar (God); this power of (primary) creation is expressed by the concept of a "Secret Fire" or "Flame Imperishable".The term for the material universe is "Eä", "the World that Is", as distinguished from the purely idealist pre-figuration of creation in the minds of the Ainur.Eä contains our Earth (and solar system) in a mythical ancient past, of which Middle-earth is the main continent.