You have to have a government to provide you with legal order, with stability, enforcement of property rights, enforcement of contracts, definition of rules and regulations - the rules of the game, so to speak - and to provide certain shared goods and services, public services. Several people have tried to estimate this and they come out with figures like government spending at 15% of GDP. In the modern world it has gone to 40% or above. So we are way beyond the optimal, and that is easier to say than what the optimum is.