Not so sure Anarchy is inherently unstable. It would be easy enough to test... give the Anarchists one small place in the world to call 'home' and see what happens. The problem is, this would never be allowed - not because it is inherently unstable, but because, as you suggest, owning other people is superior property. Since this is not the case in anarchist society, the source of the instability originates in those compelled to 'own' other people.
i like the Robert Higgs quote, except there's no monkeys in it.
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