4. If no country had national defense, people's average physical security would be higher than it is now, because the danger which any given country's national defense deters is attacks from the national defense of other countries.To which I respond:
Isn't this kind of like saying about the prisoner's dilemma that if there were no prisoners, there would be no dilemma?
If no country had national defense, many countries would benefit from developing "national offense" and taking over the defenseless ones. I have trouble seeing no countries having national defense as a stable outcome. (Or an outcome that could be reached given the world we live in.)
I think Arnold Kling agrees with me.