The theory behind the paper is that actual chewing stimulates a neuronal and hormonal reflex that helps to awaken the gut. Certainly, there's a great deal of appeal to that theory.

The theory behind a [debtor-in-possession] loan is that it is first among equals in the bankruptcy process,

Ultimately, in its collapse, Laos was important because it proved the validity of the so-called 'domino theory', which preached that communism - once victorious in South Vietnam - would metastasize throughout the region.

But the theory is also, once the shooting starts, negotiations stop. Then it's self-preservation.

The theory is, you're there to save a life,

are unequivocal in their support of evolutionary theory.