This helps to explain something really strange about our property law, which is derived from Roman law and has created terrible problems for jurists starting in the eleventh century. Our definition of property is that property is a relation between a person and a thing, whereby that person has absolute power over that thing. This definition doesn't make sense. For example, if you're on a desert island, you might have a deeply personal relationship with a tree on that island. You might well be talking to it every day. But do you `own' it? Well, it's kind of an irrelevant question unless someone else is there. In fact, property rights are relations, or arrangements, between people, about things.

Our notion of freedom is similarly problematic. `Freedom' is the natural power, according to Roman law, to do absolutely anything you like - except for those things you can't do, either because of the law or because somebody's going to stop you. This is like saying that `the sun is square except insofar as it is round'. And people immediately pointed this out: by this definition, everyone is `free'. Slaves are `free' - after all, they can do anything they want except for those things they can't do. So why did they develop this absurd definition?

The reason is that what Roman magistrates were imagining was in fact a relationship between two people of total power, which therefore renders one of them a `thing'. That's what slavery is all about. So you had this subtle shift in the meaning of freedom. Originally freedom meant `not being a slave', and so referred to people who had social relations. In fact the word `free' in English traces back to the same root as `friend' - free people are, as noted before, people who can make commitments and promises to others, which of course slaves cannot do. But then the definition shifts, so that it now refers to the power of the slave-owner. A `free' person becomes a person who has people they can do anything they want to, or who approaches the world as a set of properties in the same way - someone who has a personal private domain, within which they can do whatever they like. This definition has the advantage of not suggesting that freedom is unlimited except insofar as it is circumscribed. But it brings all these deeply perverse and contradictory notions into it: that freedom is not a product of social relations, but is in fact the negation of social relations. That has had a deeply insidious effect on how we look at the world.