The concern with inequality isn't just a Piketty thing. But this lecture by an obviously brilliant man, demonstrates how difficult it is to think about this issue analytically and philosophically.
My take on this lecture is that it is full of mis-steps and thus wrong interpretations. But I think the issues raised demand engagement -- as they have since the time of Adam Smith. And that they require what James Buchanan highlighted in describing the founding of the Thomas Jefferson Center for Studies in Political Ecoonomy at UVa back in the late 1950s.
The Thomas Jefferson Center strives to carry on the honorable tradition of ‘political economy’ – the study of what makes for a ‘good society.’ Political economists stress the technical economic principles that one must understand in order to assess alternative arrangements for promoting peaceful cooperation and productive specialization among free men. Yet political economists go further and frankly try to bring out into the open the philosophical issues that necessarily underlie all discussions of the appropriate functions of government and all proposed policy measures. They examine philosophical values for consistency among themselves and with the ideal of human freedom.