Besprechungsaufsatz

most a reaction against this descent into barbarity. The United Nations have become the focal point for a myriad of goals and values transferred to the international plane in the hope that from there they should be reflected to the national level, emboldened and strengthened as legal norms. These hopes have become reality in particular with regard to human rights. However, beyond this subject, there are many areas in UN law where similar developments have taken place – some closely connected to human rights, while some have widely emanci- pated from core human rights discussion. Thus, the concept of the »community of states« was propagated in order to argue for obligations and aims whose coming into life cannot be explained taking solely recourse to the principle of reciprocity, a principle which is, however, still the most important generator of international law obligations. Closely re- lated to this process was the introduction of the erga omnes obligations and of the jus cogens concept to which Art. 53 of the Vienna Convention on the Law of Treaties refers. There can be no doubt that these principles have found very broad, although not universal recognition. Nonetheless, they are of a rather abstract nature and they are in need for further specification as to their material content. After many attempts to give structure to all these goals and desires an ever growing consensus seems to take shape that the principle of solidarity could be the ideal device to this end. The literature is burgeoning in this field. In this contribution is has been tried to take stock of these developments. To this avail a particular approach has been chosen. It has been tried to give an overall overview on the present state of the art of the discussion on solidarity in international law while elements of a review essay on recent publications situated at the heart of the solidarity discussion have been integrated. On a whole, it is argued that it is still justified to speak about »progress in international law« (a concept, as it is known, famously introduced by Manley Hudson in 1932). To take an optimistic viewpoint can help to master the most prominent present-day challenges in international law. In this context reference to the principle of solidarity can be most useful.