America should focus on global public goods

America is currently transfixed with the problem it has created for itself in Iraq, but the presidential candidates are also beginning to ask what principles should guide the United States' foreign policy after Iraq. In my view, a focus on global public goods - things everyone can consume without diminishing their availability to others - could help America reconcile its preponderant power with others' interests.

Of course, pure public goods are rare. Most only partially approach the ideal case of clean air, where none can be excluded and all can benefit simultaneously. Combating global climate change is probably the most dramatic current case.

If the largest beneficiary (such as the US) of a public good does not take the lead in devoting disproportionate resources toward its provision, smaller beneficiaries are unlikely to be able to produce it because of the difficulties of organizing collective action when large numbers are involved. While this responsibility often lets others become "free riders", the alternative is no ride for anyone.