"I'm trying not to say that I'm not accountable."
--Lieutenant General Kevin Kiley, Walter Reed Hospital's former commander

Now that the Democrats in Congress can hold hearings with sworn testimony, the word "accountability" has finally become a staple of the daily news. But what, exactly, does "accountability" mean?

Accountability is what is called a contested concept, that is, a concept with different meanings for different people, depending on their values. What we have...