WHAT happy inspiration suggested Chaucer's greatest work, and whether it was a flash of emulation or of unqualified originality, it is impossible now to say; but there is no doubt that before the idea of The Canterbury Tales commended itself to him, and before he wrote the prologue, Chaucer had already written the tales of Custance and of Griselde, the Life of St. Cecilia, and the romance of Palamon and Arcite. Possibly also he was midway in the " tragedies " which he later associated with the Monk.