At the time there was no good theory to account for the range of cannon.

For example, a good psychological theory may be possible to prove wrong.

"The middle school concept is based on a good theory," she said.

One and another he had heard a good many theories in the course of his existence.

A good theory, but sometimes tough to put into practice.

A good theory, but in practice the culture clash was devastating.

Well, a good theory should be able to cover a wide range of cases.

There is no good theory for the structure of liquid water.

Reproduction is a good theory, and you should stick with it.

It was a good enough theory, though a surprising one.