My Sixth will propound riddles the solution of which may be attempted only by a generation which has absorbed and digested my first five symphonies.' Thus Gustav Mahler, writing in 1904 to his biographer Richard Specht. Mahler did nothing to help solve the riddles, and these words are his only authentic statement regarding this most difficult symphony. It remains puzzling, beginning with the discrepancy between this fatalistic music that ends in total collapse and his situation at the time (1903/1904).