A wildly imaginative, hilariously provocative and deeply moving play from one of Scotland's most important playwrights. The philosopher David Hume and the father of modern economics, Adam Smith, wake up in Edinburgh in the early twenty-first century. To their bewilderment, joy and horror, it is a world where all the knowledge they ever dreamt of is at everyone's fingertips and the utopia of a free-market economy is a reality. But at what cost to the planet and to humanity? With their fellow traveller, Eve, a Scottish everywoman, Hume and Smith embark on an extraordinary journey of enlightenment - from the concrete New Towns of Scotland's central belt, to Silicon Glen, ecstasy and the gay clubs of Edinburgh. Jo Clifford's play The Tree of Knowledge was first performed at the Traverse Theatre, Edinburgh, in 2011.