Abstract: Over the past 70 years, human progress founded on economic growth has been expressive in practically all areas. Nevertheless, doubts concerning the continuity and extension of these advances are mounting. Economic growth has been bankrolled by the unsustainable use of non-renewable resources, by the destruction of biological diversity and by the emission of greenhouse gases that have triggered global environmental crises while also increasing the gaps between rich and poor. Serious ecological, economic and social problems in the context of deepening globalization pressure us to rethink development in the light of nature’s own limits. This paper examines the interactions between the main conditioning economic, social and political factors of the present crisis. It also observes that current dilemmas modify the meaning and the direction of traditional debates on the role of demographic dynamics in this equation. “Sustainable development”, though much desired, has become an oxymoron. Given the increasing difficulties in conciliating economic growth, social well-being and environmental sustainability, the Three Pillars of the Rio + 20 Conference have morphed into a trilemma.