This was a great theory but extremely difficult to put into practice.

The case is closed, and even a great theory is not going to reopen it.

He is a man of grand words, learned quotations, great theories and threatening speeches.

Yes, yes, great theory - but when did you last bet your kids in a lottery?

What he did in 1961 produced the great theory about on any given Sunday.

Well, this was the great theory, but I've not seen any evidence that private landlords are reducing rents.

What a great theory, one size fits all.

And Einstein's other great theory, special relativity, holds that to be impossible.

Now the great theory that investors have learned from academics is that stocks are always the best long-term investment.

Ooh, that's a great theory - I'm going to tweet that immediately.