http://www.nytimes.com/2003/03/23/magazine/23WWLN.html
Michael Ignatieff: “It is impossible to be certain that improving the human rights of 25 million people is worth the cost because no one knows what the cost will be.” True, no one can know exactly, but it’s certainly possible to assign probabilities (or probability distributions) to the potential outcomes.
Actually, I wonder how much of the disagreement between the pro-war and anti-war camps is over matters of principle, and how much is over matters of fact. Does the pro-war side think the war will be over in 3 weeks, with 1,000 casualties? Does the anti-war side think the war will be over in 3 months, with 100,000 casualities? (I am simplifying; there are certainly many other factors.)
The Red Cross, for example, has medical supplies for 180,000. Does the military think 180,000 will require medical treatment?