To begin with, the Middle Ages differed from our own time in the very general use then made of Latin, both in writing and speaking. In the thirteenth century, and long after, all books that made any claim to learning were written in Latin;[159] the professors in the universities lectured in Latin, friends wrote to one another in Latin, and state papers, treaties, and legal documents were drawn up in the same language. The ability of every educated person to make use of Latin, as well as of his native tongue, was a great advantage at a time when there were many obstacles to intercourse among the various nations. It helps to explain, for example, the remarkable way in which the pope kept in touch with all the clergymen of western Christendom, and the ease with which students, friars, and merchants could wander from one country to another. There is no more interesting or important revolution than that by which the language of the people in the various European countries gradually pushed aside the ancient tongue and took its place, so that even scholars scarcely ever think now of writing books in Latin. In order to understand how it came about that two languages, the Latin and the native speech, were both commonly used in all the countries of western Europe all through the Middle Ages, we must glance at the origin of the modern languages. These all fall into two quite distinct groups, the Germanic and the Romance. [Sidenote: The Germanic languages derived from the dialects of the German barbarians.] Those German peoples who had continued to live outside of the Roman Empire, or who, during the invasions, had not settled far enough within its bounds to be led, like the Franks in Gaul, to adopt the tongue of those they had conquered, naturally adhered to the language they had always used, namely, the particular Germanic dialect which their forefathers had spoken for untold generations. From the various languages spoken by the German barbarians, modern German, English, Dutch, Swedish, Norwegian, Danish, and Icelandic are derived. [Sidenote: The Romance languages derived from the spoken Latin.]