What to do when faced with moral dilemmas in world politics such as the putative trade-offs between amnesties and criminal tribunals, humanitarian intervention and self-determination, the vexing conundrums presented by immigration or the exclusionary identity dynamics involved in expanding peaceful communities? Are policies which fall short of desirable ethical objectives ideals nonetheless justifiable, including practices of evident hypocrisy? How do we really know we have reached an ethical limit, or fallen short in ways that deserve the withholding of moral praise? This volume has sought to shed light on such questions, on the premise that research programmes which have shown how moral norms arise and have an impact on world politics ought to be well placed to help us answer the ethical question of ‘what to do’. We have sought here to leverage the constructivist agenda of theorising and empirically explaining how moral norms matter towards the normative project of identifying plausible moral alternatives to deal with global challenges. We explicitly recognise that constructivism is but one possible path to take to do so, and enjoin others for their contributions in thinking further through the relationship between the empirical and the normative. This volume offers its contributions in the spirit of fruitfulness and in the hope of inviting other theoretical approaches in International Relations and other disciplines such as philosophy to draw upon and critique and build upon these efforts, and ultimately to engage with practitioners in dealing with the central challenges of contemporary global politics which unavoidably have ethics at their core.