From the Introduction, one of my favorite passages in the book, and one that really sets the methodological basis for the whole argument:

“I should perhaps add that I experienced the American dream at the age of twenty-two, when I was hired by a university near Boston just after finishing my doctorate.  This experience proved to be decisive in more ways than one.  It was the first time I had set foot in the United States, and it felt good to have my work recognized so quickly.  Here was a country that knew how to attract immigrants when it wanted to!  Yet I also realized quite soon that I wanted to return to France and Europe, which I did when I was twenty-five.  Since then, I have not left Paris, except for a few brief trips.  One important reason for my choice has a direct bearing on this book: I did not find the work of US economists entirely convincing.  To be sure, they were all very intelligent, and I still have many friends from that period of my life.  But something strange happened: I was only too aware of the fact that I knew nothing at all about the world’s economic problems.  My thesis consisted of several relatively abstract mathematical theorems.  Yet the profession liked my work.  I quickly realized that there had been no significant effort to collect historical data on the dynamics of inequality since Kuznets, yet the profession continued to churn out purely theoretical results without even knowing what facts needed to be explained.  And it expected me to do the same.  When I returned to France, I set out to collect the missing data.

To put it bluntly, the discipline of economics has yet to get over its childish passion for mathematics and for purely theoretical and often highly ideological speculation, at the expense of historical research and collaboration with the other social sciences.  Economists are all too often preoccupied with petty mathematical problems of interest only to themselves.  This obsession with mathematics is an easy way of acquiring the appearance of scientificity without having to answer the far more complex questions posed by the world we live in.  There is one great advantage to being an academic economist in France: here, economists are not highly respected in the academic and intellectual world or by political and financial elites.  Here they must set aside their contempt for other disciplines and their absurd claim to greater scientific legitimacy, despite the fact that they know almost nothing about anything.”

It is a testimony to the incorrigibility of the economics profession in America that the most substantial critique of Piketty’s work to emerge from that quarter is that “Unless I’m missing something, the formal [mathematical] apparatus in Piketty’s book simply is not capable of generating the results he touts.”  In other words, “Sure he’s demonstrated that something actually happened historically, but he hasn’t proven mathematically that it’s capable of happening!”