MARCUS AURELIUS (A.D. 161-180).--Hardly less eminent for his virtues was the next in the succession of sovereigns, _Marcus Aurelius_ (161-180). "A sage upon the throne," he combined a love of learning with the moral vigor and energy of the old Roman character, and with the self-government and serenity of the Stoic school, of the tenets of which he was a noble exemplar as well as a deeply interesting expounder. A philosopher was now on the throne; and his reign gives some countenance to the doctrine of Plato, that the world could be well governed only when philosophers should be kings, or kings philosophers. He endured with patience the grievous faults of his wife _Faustina_, and of his brother by adoption, and co-regent, _Lucius Verus_. He protected the eastern frontier against _Parthia_. In the war with the _Marcomanni_, he drove the German tribes back over the Danube, and gained a signal victory over the _Quadi_ in their own land. His great object was to strike terror into the barbarian enemies of the empire on the north, and prevent future incursions. Although victorious in many of his battles, he failed to accomplish this result. The danger from barbarian invasion increased with the lapse of time. Before his work was finished, _Marcus Aurelius_ died at _Vindobona_ (Vienna), in March, 180. During his reign, there was persecution of Christians. Especially the churches of _Lyons_ and _Vienne_ have left a record of their sufferings. The virtuous emperors, who were strenuous in their exertions to maintain the old laws and customs, were apt to be more severe in their treatment of Christians, whom they ignorantly regarded as a mischievous sect, than were those emperors who were men of looser principles.