The Treaty on European Union (EU) has on the one hand increased democratic legitimacy of the integration process by confering new powers to the European Parliament (EP) - legitimacy viewed as an attribute-, while on the other hand acceptance by the citizens - legitimacy conceived as orientation - dropped considerably after Maastricht. This situation hints at a paradox and highlights the need for a more complex approach to the issue of legitimacy of the EU and the role played by the EP. As a first step, we identify different views on the role of the European Parliament: a federalist and a realist one. Further, they are contrasted with empirical findings about the role and function of the EP after Maastricht, using three main dimensions: policy-making, system-development and interaction with the citizens. Taking into account the results of this inquiry, we present a new perspective on the EP based upon a view of the EU as a new kind of political system characterised by fusion. It is a major feature of this new kind of political system that national, subnational and supranational actors merge their instruments to 'produce' political decisions. The result is a mixed polity whose legitimacy is neither based on a collective personality called 'the people' nor on the single peoples of the member states only, but on a 'pluralistic citizenship' as a 'unity-in diversity'. Legitimacy as an attribute must be defined in new terms deviant from national experiences, entailing - at least partly - a lack of transparency, increasing complexity and growing differentiation. Is Legitimacy possible despite these apparant drawbacks? This question hints at an ambiguous, but also 'productive' tension within the EU system as a whole and with regard to the role and position of the EP in particular.