But McNamara did have one very simple argument for multilateralism based on the limits of reason. He said the problem with reason is that we tend to see what we want to believe, and the only check on this is another perspective. And for that reason alone, he states unequivocally that the US should never go to war unilaterally. Because if we can't make our case to other countries who share our values, it means it's not a good enough case. He says if we'd followed this simple rule, there never would have been a Vietnam, because all of our allies were against it: Germany, Italy, Britain, France.
Mind you, it won't prevent all mistakes. It wouldn't have prevented the Kosovo war when other options were possible. But it wouldn't be a bad first cut.
Michael