This goes back to a point I was making a while ago about how dangerous it is that the public discourse is so dominated by low-quality freelance philosophy done by people with PhDs in economics. I’m fairly certain that if Mankiw were to walk over to Emerson Hall he could find some folks (possibly T.M. Scanlon who I know sometimes reads this blog) who could explain to him that there’s little grounds for the belief that a commitment to utilitarianism is the main justification for redistributive taxation.
…the point here is that the marginal utility of money income declines as it grows. This is also a strong argument for believing that redistributing money from wealthy or high-income individuals to the poor or to public services will be welfare-enhancing.