xi should hope for "first and foremost" from any historical investigation, including his own, was that "it may not be too tedious. " II That hope is generally realized in Mach's historical writings, most of which are as lively and interesting now as they were when they appeared. Mach did not follow any existing model of historical or philosophical or scientific exposition, but went at things his own way combining the various approaches as needed to reach the goals he set for himself. When he is at his best we get a sense of the Mach whom William James met on a visit to Prague, the Mach whose four hours of "unforgettable conversation" gave the