Facts alone have limited use and lack meaning; a valid theory organizes them into far greater usefulness.

This may be a valid theory about the second novel but not Ali and Nino.

This criticism was valid in the early days of the human capital theory but not later when attempts were made to be more specific.

That a golfer has to be an entrepreneur is an absolutely valid theory.

Those rules now require inclusion of "other valid scientific theories" along with evolution.

Thomas Breuer in 1994 had proven that physical theories valid for the whole universe are impossible.

That looks a much more valid theory now that the Hivers have reacted.

By 1933, the molecular orbital theory had been accepted as a valid and useful theory.

Had the psychiatrist, on the basis of today's first visit, any valid theory?

For example, some people continue to argue that evolution isn't a valid scientific theory because it can't be tested.