Recently, European integration (EI) and international relations (IR) debates have been locked into two camps: rationalists, modelling themselves on the natural sciences, and reflectivists, opposing themselves to the natural sciences. The division is based on an out-of-date view of the orderly nature of the natural sciences. Since the middle of the twentieth century a new complexity framework in the natural sciences has developed. This framework provides a new and intriguing ontological and epistemological foundation for addressing the problem of complexity and helps to explain and overcome the separation between the two poles of debate in European integration and international relations.