The one phrase I have not heard in any debate over government policy in my lifetime is: "I don’t know." From the Cuban missile crisis to the latest debates over heath care, Republican and Democratic administrations alike have never encountered a question for which they have no answer.

Both Democrats and Republicans "knew" that if Vietnam fell, the rest of Southeast Asia would become communist. It didn’t happen.

The same folks "knew" the Russians wanted to occupy Disney World or nuke it out of existence. An arms race was pursued that bankrupted the former Soviet Union and left the United States with the crippling burden of an uncontrolled military-industrial complex.

The same people have terrorized the American public with imagined threats from al-Qaeda, a group of poorly organized and largely ineffectual people who got lucky once. Now we spend millions of dollars defending against ever more unlikely threats.

The common thread across these events? No one would say: "I don’t know what will happen."

There are lots of policy questions, whether you are liberal or conservative, where we simply don’t know what will happen. And in some cases it isn’t possible to know.

If policy discussions could start off with that honest admission, we could discuss what we don’t know and, in some cases, ways to find answers.