The history of later days was full of notes upon religion. Cæsar interspersed them among the narratives of his campaigns in Gaul; Tacitus drew on his recollections as {41} an officer in active service for his description of the Germans. There was as yet no literature in Wales or Ireland to embody the Celtic traditions; and the Scandinavian Saga was unborn. But the geographers, like Strabo (first century A.D.), collected a great deal of material that must have been gathered ultimately from travellers, soldiers, traders, and slaves. A wise and gentle philosophic Greek, Plutarch of Chæronea in Bœotia (A.D. 46-120), student at the university of Athens, lecturer on philosophy at Rome, and finally priest of Pythian Apollo in his native city, is at home in many religions. Beside altars to the Greek gods Dionysus, Herakles, and Artemis, in his own streets, were those of the Egyptian Isis and Anubis. The treatise on Isis and Osiris (commonly ascribed to him) is an early essay in comparative religion. In the latter half of the second century the traveller Pausanias passes through Greece, describing its sacred sites, noting its monuments, recording mythological traditions, and observing archaic rites. In this fascinating guide-book to religious practice are survivals of ancient savagery, still lingering at country shrines, set down with curious unconsciousness of their significance. The historical method is as yet only in its infancy. But Pausanias rightly discerned that its first business is to know the facts. In Rome, where ritual tradition held its ground with extraordinary tenacity amid the {42} decay of belief, Marcus Terentius Varro, renowned for his wide learning (116-28 B.C.), devoted sixteen books of his great treatise on Antiquities to "Divine Things." Like so many other precious works of ancient literature it has disappeared, but its contents are partly known through its use by St. Augustine in his famous work on "The City of God." Following a division of the gods by the chief pontiff Mucius Scævola, he treated religion under three heads. In the form presented by the poets' tales of the gods it was mythical. Founded by the philosophers upon nature (_physis_) it was physical. As administered by priests and practised in cities it was civil. It was an old notion that religion was a legal convention imposed by authority for purposes of popular control; and Varro does not disdain to declare it expedient that States should be deceived in such matters. This police-notion long regulated public custom, and tended to render the identification of deities presenting superficial resemblances all the more easy.