St. Thomas Moore had his Utopia, Marx and Engels had their Communist Manifesto. Though the latter is better known for the destructive nature of its implementation in this and the last century, it has a commonality with the other books mentioned: the necessity of authoritarianism. It is this need for an authoritarian form of government and a ruling class, either explicit as in the Republic or implicit as with Marx and Engels that binds most, if not all Utopian systems with each other.