In the authors' view, to proceed from the baseline of market distributions of social welfare - - which most people agree would allow serious and troubling social outcomes - - is to utilize a market-centric conception of social justice. As all citizens are first that, i.e. citizens, all have a stake in the social compact and all must be the equal concern of the governing organs of the state. Thus, all have a right to live lives free of poverty and the inequalities allowed by pure market outcomes.
Those tax commentators proceeding from the market baseline are those whom the authors call 'unreflective libertarians.' They are those who believe that they first owneth, and the government taketh away, and that their claims to ownership of their incomes and assets do not require government validation. The authors argue, conversely, that the only ownership we have is what government considers permissible (after taking Dworkin's maxim into account).
Murphy and Nagel argue that ownership, since only legitimized by government, is almost completely dependent upon government. To justify their position they invoke Hobbes and they assert that the 'state of nature' prior to the formation of government was a Hobbesian war of all against all. Thus, government, and robust government at that, performs more than a regulative role but is the condition sine qua non for the possibility of ownership, property rights, wealth and even civility.
While one might have sympathy for where Murphy and Nagel want to take us, their utilization of Hobbes to demonstrate the near heirophanic role of government is precisely what leads to many of their critics' charges of statism. Their argument could have proceeded without such strong claims (assertions, really) about human nature and government. Many conservatives would argue that government does not only NOT provide OF ITSELF the conditions for the possibility of ownership and property, they would argue that government at times impedes those conditions in unfair and inappropriate ways. As well, there are those who would argue that the authors' assessment of human nature is too dark, although convenient to their argument that it is government, and not social actors, that creates the legitimacy for claims of ownership and property rights, etc. Many would point out, in fact, that 'constitutional conventions' precede constitutions and thus that legitimacy flows from the people and the people's moral deliberations and not from government per se (Where, in fact, does non-despotic government obtain its legitimacy but from the people?).
The argument in the Myth of Ownership rests upon philosophical pillars that are unhelpful to its case and which lead to conclusions that are both philosophically problematic and politically fatal in a Western context, and so its central argument fails. Few would disagree with the claim that wealth and ownership are helped along by governmental frameworks, some safeguards against unjust seizures etc. But, I would have to reject Myth's statism, it's dark view of human nature, and so I come away disappointed at what promised to be a rubber-meets-the-road philosophical essay. It would have been a better book if the authors grounded the legitimacy of ownership and property rights claims in the moral imagination of human beings, rather than in Leviathan.
The entitlements approach to justice is more in tune with the common law and history than the idea of collectivist "creation" of "rights", "offences" or "social mortgages".
As Pitt the Elder observed, taxation and the common law are strangers (which is why taxation statutes reeived a strict construction against the Crown).
I could go on but why? If this sort of stuff gets published I should have a go myself!