Certainly, the American people have a right to insist that our government operate with a clear vision of success and that it develop a clear plan for evaluating whether we are moving in the right direction, even if no tidy numerical metrics can meaningfully size up so complex a human endeavor. As shown here, supporters of the current strategy do indeed have a clear definition of success, and those working to implement it are already evaluating American progress against that definition every day. It is on the basis of their evaluation that we say the surge is working.

http://www.aei.org/publications/filter.,pubID.27890/pub_detail.asp