Humans contest for control or ownership. Contest is to a considerable extent inescapable because conceptually a large part of most grammars involve possession and appropriation. Language creates antithesis (‘mine, yours’) that results in conflict. The result of conflict is possession and dispossession, which results in ownership, which is expressed in property and property systems. This dissertation focuses on the exclusionary effect of property systems. Property confers the power to exclude and the aggregate of legal exclusions, which constitutes a property system, objectively or instrumentally creates social exclusion and thus social inequality. Income and property tax facilitate redistribution, reducing social inequality. Another mode of reducing/diffusing the exclusionary effect of ownership is to enlarge the public domain, which I define as a commonwealth of non-control and non-ownership