From the very outset, the aim of environmental policy integration – the integration of environmental aims into other policy areas – has constituted a central pillar of the EU's environmental policy. Unlike certain other EU policy fields, the aims of EU environmental policy, as set out in Article 191(1) TFEU, cannot, by their nature, be achieved using a sectoral approach adopting a strict demarcation between policy areas. The EU's numerous efforts in recognition of this fact were discussed in Chapter 3. From a legal perspective, these culminated in the Treaty of Amsterdam's insertion of what is now Article 11 TFEU into the overarching principles of the Treaty. From a policy perspective, the European Council's launch of the Cardiff process, under which different formations of the Council of Ministers were requested to develop strategies to achieve environmental integration, ensued. This was followed by the Gothenburg declaration that the EU's Lisbon Strategy was built on three pillars – economic, social, but also environmental.