Luther's journey from Wittenberg and his appearance in Worms were a demonstration of his popularity throughout Northern Germany. Charles V., youth as he was, was too clever a politician to offend too deeply at this outset of his reign a whole people whose services he might at any moment sorely need. He heard Luther with patience, he respected his safe-conduct, and let him return to Saxony in safety; but he published as the formal decision of the Diet the Edict of Worms, wherein Luther was declared in the ban of the Empire as he was already in the ban of the Church, and his books were condemned to be burned wherever found. The Edict of Worms defined the official attitude of the Empire towards the reform from this time forth. It lacked nothing in clearness and finality. Henceforth, whoever within the limits of the Empire harboured either the man or his ideas was subject to immediate punishment. The question, however, still remained, how the Edict of Worms was to be enforced, and the answer to that question is the history of Germany and even of Europe for the next generation. Enough for our present purpose to say that the immediate pressure of political and military demands outside of Germany compelled the young emperor to postpone definite aggressive action against the Lutheran party until the course of events had separated the whole north of Germany from all but a nominal connection with the Empire. We are concerned with the action of Erasmus upon these events and their reaction upon his course of life. Erasmus left Louvain in 1521. As to his motives in this change we are as much in the dark as about any of his former migrations. We know what his critics said about it and what he replied to their criticisms. They said he was afraid to stay in a country where heretics were being arrested every day and where, as he had all along been declaring, he was regarded as the head and front of this whole offending. He replied that this was pure nonsense, as could be clearly proved by the fact that after leaving Louvain he still lingered for several months in the Low Countries before taking up his journey to Basel. He went to Basel, he said, for the same reasons which had carried him thither before; namely, to superintend the publication of some of his works. The most detailed account of this interval between Louvain and Basel is given in a long letter,[141] dated in 1523, to Marcus Laurinus, dean of St. Donatian at Bruges. The tone of this letter is that which had now become habitual with Erasmus, namely, of elaborate defence against all charges, no matter from what source, which could in any way affect his loyalty to the Roman Church on the one hand or to his own principle of free criticism on the other. His especial grievance is the charge of cowardice in leaving Louvain. [141] iii.¹, 748.