I liked this part from one of Matthew Yglesias's posts regarding Barack Obama's win of the Democratic nomination:

Relative to Clinton, you see two people with similar policy agendas. But Clinton comes from a school of politics that says liberalism can't really win on the questions of war and peace, identity and authenticity, crime and punishment. It says that we live in a fundamentally conservative nation, and that the savvy progressive politician kind of burrows in and tries to make the best of a bad situation. It's an attitude very much borne of the brutally difficult experience of organizing for McGovern in Texas and running for governor in Arkansas at the height of Reaganism. Relative to McCain, Obama thinks it's possible to accomplish things in the world. He thinks the United States faces a lot of serious international challenges, but doesn't see them as primarily driven by menacing and implacable foes. Obama thinks that a combination of visionary leadership and shrewd bargaining can greatly improve our ability to tackle key priorities without any great expenditure of our resources.

I have a friend whose physicist father likes to note that knowing a solution is possible is a huge help to finding that solution. In an arena as complex as, oh, fixing the world, finding future "solutions" requires both a healthy attachment to facts and evidence and a healthy ability to guess and approximate, to dare, to insist. Can we balance these demands, dramatically changing our future course without succumbing to either foolhardy risk or mind-numbing caution? I think the answer is yes, yes we can.