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. Eä (Quenya for let [these things] be!) was the word spoken by Eru Ilúvatar to bring the physical universe into actuality.