Many literary critics seem to think that an hypothesis about obscure and remote questions of history can be refuted by a simple demand for the production of more evidence than in fact exists. The demand is as easy to make as it is impossible to satisfy. But the true test of an hypothesis, if it cannot be shown to con?ict with known truths, is the number of facts that it correlates and explains. Francis M. Cornford 1914] 1934, 220. It was in the autumn of 1997 that the research project leading to this publication began. One of us GH], while a visiting fellow at the Center for Philosophy of...