The issue of climate change is one that we ignore at our own peril. There may still be disputes about exactly how much we're contributing to the warming of the earth's atmosphere and how much is naturally occurring, but what we can be scientifically certain of is that our continued use of fossil fuels is pushing us to a point of no return. And unless we free ourselves from a dependence on these fossil fuels and chart a new course on energy in this country, we are condemning future generations to global catastrophe.

Hillary Clinton has been in politics for the same reason I am - because we can improve other people's lives by doing this work.

Chancellor [Angela] Merkel is perhaps the only leader left among our closest allies that was there when I arrived. So in some ways we are now the veterans of many challenges over the last eight years.

I'm not going to Wall Street [after the presidency]. The amount of time that I'll be investing in issues is going to be high. But it'll be necessarily in a different capacity.

Throughout history, Islam has demonstrated through words and deeds the possibilities of religious tolerance and racial equality.

I find it amusing that those who helped to authorize and engineer the biggest foreign policy disaster in our generation are now criticizing me for making sure that we are on the right battlefield and not the wrong battlefield in the war against terrorism.

What I believe unites the people of this nation, regardless of race or region or party, young or old, rich or poor, is the simple, profound belief in opportunity for all - the notion that if you work hard and take responsibility, you can get ahead.