What is wrong with this idyllic picture of life without the state? One major problem is that it relies on small, tight-knit communities as the basis for social order, and although in the past this might have been a reasonable assumption to make, it no longer is today. We live in societies that are highly mobile, both in the sense that people can move around physically quite easily, and in the sense that there is a ready supply of new people to collaborate with, and also, unfortunately, to take advantage of. The anarchist picture is not nonsense, but it works on the assumption that we will interact over time with the same group of people, so that the way we behave becomes common knowledge in the group. It also assumes that the possibility of being excluded from the group is a powerful deterrent to antisocial behavior. But in a large, mobile society that assumption does not hold. We need, therefore, a legal system that will track down and punish people who injure others, and that allows us to make binding agreements with one another that carry a penalty if we default.