The question of how inequality is generated and how it reproduces over time has been a major concern for social scientists for more than a century. Yet the relationship between inequality and the process of economic development is far from being well understood. These Raffaele Mattioli Lectures have brought together two of the world's leading economists, Professors Philippe Aghion (a theorist) and Jeffrey Williamson (an economic historian), to question the conventional wisdom on inequality and growth, and address its inability to explain recent economic experience. Professor Aghion assesses the affects of inequality on growth, and asks whether inequality matters: if so why is excessive inequality bad for growth, and is it possible to reconcile aggregate findings with macroeconomic theories of incentives? In the second part Jeffrey Williamson discusses the Kuznets hypothesis, and focuses on the causes of the rise of wage and income inequality in developed economies.