I am interested in exploring the application of principles of justice to world politics. I have developed and defended a 'cosmopolitan' account of political morality in my book Justice Beyond Borders: A Global Political Theory (Oxford: Oxford University Press, 2005). (For more information and for reviews see Justice Beyond Borders.) I am completing a second book on global justice, entitled On Cosmopolitanism (Oxford: Oxford University Press, forthcoming). I have a completed manuscript, which has been discussed at four workshops. The workshops were held at the University of Essex (4th November 2016), the University of Birmingham (20th January 2017), Goethe-University, Frankfurt (27th January 2017), and Louvain-la-Neuve (15th March 2017). I am now revising it before submitting it for publication. For further information about the book see here.
In addition to this, I have published papers on the following themes in particular
 Global Poverty. I have argued that persons have a human right not to suffer from poverty and have identified the set of negative and positive obligations of justice that this entails. (For my treatment of these issues see Global Poverty.)
 Global Inequality. One widely held view is that all persons should be above a certain threshold standard of living, but that inequalities in people's opportunities or standard of living above that threshold is not unjust. I have argued against this in a number of papers and defended a principle of global equality of opportunity. (For my treatment of these issues see Global Egalitarianism.)
 Methodological Issues. Some defend global principles of justice on the grounds that justice applies to persons who are in a certain kind of relationship (maybe membership in a nation or economic interdependence or common subjection to a coercive power). I argue against this associational approach and a defend a non-associational view, according to which principles of justice (including egalitarian principles of justice) can and do apply among people even if they are not linked by these kinds of relationship. (For my treatment of these issues see Humanity-Centred Cosmopolitanism.)
 Environmental Sustainability. Global theories of justice - either implicitly or explicitly - make assumptions about the environment. For example, realising some principles of distributive justice requires certain environmental preconditions (clean water, access to food). At the same time, many of the activities that principles of justice permit have environmental impacts and we face serious environmental challenges. These raise a number of important questions: What limits does a concern for the environment place on people's actions? Who is responsible for preventing environmental degradation? Since demographic change and population growth have major environmental impacts, how should we think about these? (For my treatment of these issues see Global Environmental Justice and Environmental Sustainability.)
 Global Institutional Design. The realisation of global principles of justice has implications for institutional design. If we are committed to global principles of civil, political and economic justice should we endorse a system of states? Should we call for a world state? I have argued in support of a system of multilevel governance, calling for democratically accountable institutions at global, transnational, state-level and sub-state level. (For my treatment of these issues see Global Institutional Design.)
 Responding to Injustice. Principles of justice generate obligations on duty-bearers and they may call for institutional change. What, however, should be done, and by whom, when powerful actors fail to comply with their responsibilities? I have written several papers examining what those who bear the brunt of global injustice are entitled to do so secure their own rights. (For my treatment of these issues see Responding to Injustice.)
 Cosmopolitanism. The view that I defend in (1)-(6) is often described as a 'cosmopolitan' position. For an analysis of cosmopolitanism see Cosmopolitanism.)
 Other topics. In addition to the above, I have also published papers on several contemporary thinkers including Brian Barry (on multiculturalism), Charles Beitz (on his defence of cosmopolitanism), Rainer Forst (on the basic right to justification), David Miller (on his critique of cosmopolitanism), Onora O'Neill (on the agents of justice), and John Rawls ('The Law of Peoples'). (For details see Analyses of Contemporary Philosophers).