A little theory and a lot of practice," he said.

Her personal theory said that one father could do more to mess up a child's life than every mother in existence put together.

One theory says that tigers evolved in the far north.

There are reasons to believe some significant portion of what the theory says.

Her theories, however, did not say what that change might be.

Some theories of economics say ethics has to do with money.

But as is often the case, what economic theory says and what happens are two different things.

The theory says nothing whatever about what fluctuations may occur during the year.

The same theory says that space and time are elastic.

If the economic system were fair, this theory says, there would be no crime.