One of the issues frequently raised when the EU's role as a normative actor is considered is that of consistency/variation in its approach. Much of this has centred around a norms–interests dichotomy, and the question as to which carries most weight. While political and economic interests have clearly played an important role in EU development policy, offering an explanation for much of the geographic differentiation in its application, our argument here is that apparent inconsistencies are not necessarily reducible to a violation of norms or the prioritising of interests, but may be explicable through recognition of a further factor – a 'theory filter'. From its inception in the form of Association following the signing of the Treaty of Rome, through the Yaoundé and Lomé Conventions and on to the Cotonou Agreement, the EU's approach to development has undergone a fundamental transformation over time. Nevertheless, the normative identity of the Union has, over the same period, remained relatively stable. Intrinsic to this has been the way in which development itself has been conceived and understood. Development theory has in effect acted as a filter through which European norms have passed into EU development policy, meaning that key changes in policy have been linked to the evolution in conceptual issues of development, rather than to inconsistent application of norms or the prioritisation of other interests. The paper explores this process, examining the linkage between policy change and conceptual change from the advent of Associationism in 1957 through to the present post-Cotonou and (soon) post-MDG period, with agreement on new global Sustainable Development Goals envisioned for 2015.