  The free rider problem gives rise to large explanatory and normative questions in six main disciplines. Social psychology asks: To what extent and in what circumstances are people motivated to free ride? and What sorts of negative incentives are effective in motivating cooperation when free riding is possible? Game theory asks: Under what strategic circumstances does the rational promotion of individual self-interest recommend free riding? Informed by those two areas of enquiry, mainstream economics then asks: What real-world mechanisms are the most efficient ways of producing public goods, given the incentives to free ride? Political science asks: What explains the existence of large-scale political participation, despite the incentives that favor free riding? Moral philosophy asks: Under exactly which circumstances is free riding morally wrong? and What explains why it is wrong (when it is)? And relatedly, normative political philosophy asks: Do the moral reasons against free riding supply a satisfactory grounding for political obligation?