Jamie, 2 things:
Firstly, about the Somalia.
I am not going to hold Somalia up as an example of how anarchy brings utopia. This is obviously farcical. My point was however to point out that the problems often cited regarding Somalia exist in MOST sub-Saharan African countries.
It is equally farcical to suggest that if Britain did away with the main structure of the State but retained all free associations and organizations that it would end up anything like Somalia.
Finally, statistics consistently and irrefutably show that with the fall of Barre, living standards for the bottom 90% of Somalians have risen despite all of the violence and invasion by the US and Ethiopia. Totalitarian rule is one example where even anarchy in the pejorative sense (ie. total chaos) is preferable to the State.
Obviously this case is much harder to make for a 'Western' 'Liberal' 'Democracy'.
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"Surely the only way to prevent the resumption of coercive power would require the people to be sufficiently organised to resist any individual or group attempting to exert such power. In order for the people to so organise themselves, they would need an agreed system for collective decision-making. I would argue that the people, organising themselves in this system, would constitute a form of state. No?"
Assuming that the mandate was consistently owned by the collective? No, I don't think that is a State in the form we are discussing here. (And if it is, I think we can agree it a fundamentally different type of state than a despotism, nation-state, a feudal state, and especially a modern State). You are correct of course in saying that this is to prevent a resumption of coercive power.
Fortunately, such structure already exist in the form of grassroots political communities, neighbourhoods, etc. Again, given relative prosperity and equality, and given a balance of power, coercive States do not form.
It took a very specific set of circumstances in human history for man to fall under the dominion of man, and given that those circumstances are avoided (power through moral influence, accumulation of disparate weaponry, collective inability for sustainability etc.) I see no reason why such a state cannot by maintained by a far more advanced society (or set of societies).