Thomas Piketty’s book Capital in the 21st Century was the publishing sensation of 2014. An analysis of the causes and growth of inequality, it has sold nearly half a million copies worldwide. It was described by many reviewers as the economic book not just of the year, but of recent decades.

How is it that a young, largely unknown French economist stirred up such a massive worldwide debate on inequality, a topic that Nobel Prize-winning economists such as Joseph Stiglitz and Paul Krugman have been writing about for most of their careers? The answer lies in Piketty’s main argument, backed up by his extensive research, which states that capital – whether invested in the stock market or property – will always grow faster than income. As a result, he argues, people who are already rich will carry on getting richer, while those who depend on income will never catch up. Piketty’s solution? A global redistribution of wealth that would give poorer earners some capital to invest.

In this rare appearance in London, Piketty appeared centre stage for Intelligence Squared, along with a panel of experts to debate his findings. Do the alleged inaccuracies found in Piketty’s historical data affect the premise of his book? Is he right to predict that inequality will continue to rise during the 21st century? Is the allegedly growing wealth gap a threat to democracy? And what should we make of his