In “Libertarianism Without Foundations,” Nagel criticizes Nozick for rejecting arrangements “to compel people to contribute to the support of the indigent by automatic taxation.” He argues that it is “unreasonable” to ask people to offer voluntary donations for two reasons. First, people might want assurance that others are donating; second, voluntary donations are more “irksome” than taxes.
There are several problems here. First, Nagel’s use of the term “indigent” is potentially misleading, at least insofar as he aims to defend Rawlsianism as an alternative to Nozickian libertarianism. Rawls doesn’t have in mind the starving or the homeless as the members of the worst off class—he has in mind the so-called “working poor” within a nation’s borders. Of course, there is still a case to be made for redistribution from the rich to the domestic working poor, but if we are concerned with *extreme* poverty, we ought to be concerned primarily about the global poor. (I’ll note in passing that Nozick but not Rawls requires open borders, a policy that has proven extraordinarily effective in alleviating extreme global poverty.) Furthermore, Rawls himself has no way to justify taxation to finance transfers to someone in extreme poverty who is a not "fully cooperating member of society"—say, someone who suffers from an illness that prevents them from working. So Rawlsians themselves are subject to the same sort of criticism that Nagel makes of Nozick.
Nagel also overlooks the ways in which motivated people can solve the assurance problem without compulsion, such as using an assurance contract (think of Kickstarter, but for charitable donations). I talk about this point in greater depth in chapter 4 of Unequivocal Justice.
Moreover, Nagel fails to
recognize that the assurance problem plagues the political support he and Rawls
need to implement their preferred scheme of taxation—why voluntarily cast a
well-researched and unbiased vote for progressive redistribution when you have
no assurance your neighbor is doing the same? And Nagel’s claim that paying
taxes is less irksome than authorizing an automatic monthly charitable donation
makes me think he’s had a much smoother experience with his taxes than I have.
(Jason Brennan and I discuss these last two points in detail in our paper “If You’re
an Egalitarian, You Shouldn’t Be So Rich.”)