There are few pieces of prose in any literature which draw emotion like Lenz. But then there are few writers in any language who cut through his age like Georg Büchner, cut so finely in fact that he left no trace at all on his contemporaries. Social revolutionary, clinical scientist and dramatist, Büchner's method of writing with a scalpel lay unnoticed for almost a century, until German history made it look like prophecy.

Dead of typhus in Zürich in 1837, not quite twenty-four, Büchner had two complete plays to his name, two translations of plays by Victor Hugo, a revolutionary manifesto, a dissertation on the cranial nerves of the barbel (a fish then found in the Rhine), and some disconnected sheets that were edited to 1879 to become Woyzeck, the pivotal theatre piece of the early twentieth century and a major influence on everyone from Brecht to the Expressionists. His papers also included an incomplete prose account of an earlier poet's breakdown. Like everything Büchner wrote, Lenz has its source in documents, in this case Pastor Oberlin's short sober diary of Lenz's three weeks in 1778 in the Vallee de la Bruche, a canton in the Vosges a day's walk south-west of Strasbourg. Büchner, who stayed in Strasbourg with Johann Jakob Jaeglé, the protestant pastor who gave up the orison at Oberlin's funeral in 1826, remarks in a letter to his parents in October 1835 that he had come on all sort of interesting material about one ...