Perhaps the modern reader must first realize what a curious phenomenon it is that Geoffrey Chaucer became the first English author. It would have been surprising in the fourteenth century for anyone to think of writing in his native tongue, and this was particularly true for Chaucer's role models. The first impulse for a medieval writer who was writing something he wanted remembered was to write it in Latin. Latin was considered to be the grammatica, the language which would not change, the indestructible language. Cicero wrote in it a millennium and a half ago, and Cicero is still read, so it is not surprising that around 1307-1314, when Dante started out to write the Commedia, he started in Latin. Fortunately, he started in Hell, not in Heaven, because when he discovered he did not know enough Latin words for mud, dirt, and most political intrigues, he found...