How would decision making work on a very large scale?

Question capitalism, not anarchism. If you're anarchist but not also communist, you're lost in the delusional labyrinth of capitalism. Don't stay lost there long, and even if you think you're wise you might still believe bartering is anticapitalist enough, as if trading widgets is not exactly like trading money. Bartering is primitive capitalism, just not sophisticated enough to use more advanced tools like currency... like a luddite. Acting like it's possible to create a new world of barter is anticommunist utopian socialism. It's not possible. Live and learn. The future is communist... not that nation state vanguard party garbage (don't be fooled by the capitalist propaganda), but actual real deal planetary stateless moneyless barterless no trade at all communism.

Proper anarchy has a different form of democracy than almost all anarchists assume too, even a lot of serious ancoms are pretty uninformed/misinformed about how democracy actually does and should work in anarchy or communism. It's due to old, translated, and underdeveloped words which are subject to interpretation, and miscalculations where one miscalculation leads to others.

/r/DebateAnarchism Thread