The moral force of the benefit principle

What gives the benefit principle its moral appeal as an idea of tax justice? And what can count as a benefit for that purpose? My claim is that we can trace the moral force of various versions of the principle to five ideas: individual justification, causal feedback, reciprocity, opposable valuation and non-objectionable baseline. I develop those ideas into an account of the moral permissibility of benefit-based taxation, and explain how that account addresses problems about the quantification and valuation of benefits and the relationship between benefit and the justice of the background distribution.