The future of the Earth, as described by current scientific theory.

The twins had never seen one, knew how it worked only by theory.

By our own theory that we worked out so long ago, Charles.

By your theory, he would still have been there.

I know what the theory is, but no person can live by theory alone.

By your theory they would just be - sports.

Indeed, we know as facts several things which he has not yet divined even by theory.

He managed his own, clumsily, more by theory than any actual knowledge of the art.

It also has one more syllable than the ten prescribed by theory.

Experimental 20th-century fiction is, at the same time, influenced by literary theory.