There are always going to be people who want to be president, and some days I'd like to give it to them.

Each generation of Americans must define what it means to be an American.

The most profound security threat we face today is global warming....climate change has the capacity to change the way all of us live.

President Obama started with a much weaker economy than I did. Listen to me, now. No president - no president, not me, not any of my predecessors, no one could have fully repaired all the damage that he found in just four years.

Nearly every problem has been solved by someone, somewhere. The challenge of the 21st century is to find out what works and scale it up.

At the dawn of the 21st century, a free people must now choose to shape the forces of the Information Age and the global society, to unleash the limitless potential of all our people, and yes, to form a more perfect union.

Only a fool does not look to explain his mistakes.