Words and Pictures: New Light on Plimpton 322

1. INTRODUCTION. In this paper I shall discuss Plimpton 322, one of the world's most famous ancient mathematical artefacts [Figure 1]. But I also want to explore the ways in which studying ancient mathematics is, or should be, different from researching modern mathematics. One of the most cited analyses of Plimpton 322, published some twenty years ago, was called "Sherlock Holmes in Babylon" [4]. This enticing title gave out the message that deciphering historical documents was rather like solving a fictional murder mystery: the amateur detective-historian need only pit his razor-sharp intellect against the clues provided by the self-contained story that is the piece of mathematics he is studying. Not only will he solve the puzzle, but he will outwit the well-meaning but incompetent professional history-police every time. In real life, the past isn't like an old-fashioned whodunnit: historical documents can only be understood in their historical context.