What I know for sure is that Social Security is the backbone of our country.

FORBES: Will Social Security be there for You?

But here is what I know for sure.

WHITEHOUSE: Remarks by the First Lady at a Campaign Event -- Reno, NV

But here is the thing I am so proud of -- when I travel across the country -- and I've come in and out of all kinds of communities -- this is what I know for sure.

WHITEHOUSE: The White House

This is what I know for sure.

WHITEHOUSE: The White House

What I know for sure is that the Iraqi security forces will reach the critical mass level where we have turned the tide around and the insurgents and the terrorists are on the run and we are chasing them.

NPR: An Iraqi Perspective on Ending the War

What I do know for sure is that this is a very personal decision for every individual.

FORBES: Would You Fight to Keep Your Job?

But what I do know for sure is that by subsidizing the marriage of Bear Stearns and JP Morgan, the government has removed some of the loss from the profit and loss system.

NPR: Does Bear Stearns Bailout Set a Bad Precedent?

"I'm not really sure there is an established market for this or that people do know what they're going to use it for, " said Buford.

CNN: Seeking a market for cheap 3-D printers