Does the world need a global “Tobin” tax? That is the question buzzing around London's financial circles. Some three decades ago, James Tobin, the economist, first proposed introducing a tax on financial transactions to deter short-term currency speculation. Since then few policymakers have dared air the idea since it seemed wildly unfashionable. But this month Adair Turner, chairman of the FSA, took part in a round-table organised by *Prospect magazine – and suggested a new “Tobin” debate. Unsurprisingly, this has grabbed attention. However, the really interesting thing about Turner's suggestion is the wider intellectual impetus behind it. For the FSA chairman is increasingly convinced that Western policymakers are at an intellectual watershed.