The title of this collection of essays is meant to reflect the flow of ideas in the ancient world from east to west, especially in the area around the Mediterranean. Two great rivers, the Nile and the Rhone, represent symbolically two cultural poles: Egypt, one of the cradles of civilization in the ancient world, already the repository of ancient wisdom in the eyes of the Greeks, and Gaul, younger but by the fourth century AD already the recipient of eastern influences for over a thousand years. The flow of ideas from east to west in the ancient world was particularly true of monasticism, a movement that arose in the East, in Egypt, Palestine, and Syria, then attracted travelers from the West and finally was imitated in the West. The title reflects also the author’s particular interests, which include Egyptian monasticism and early Western monasticism, especially that represented by John Cassian and those for whom he wrote in southern Gaul in the early fifth century. Through his writings Egyptian monasticism came to influence not only early fifth century monasticism in southern Gaul, but far beyond, indeed all of Western monasticism. His works were recommended by the Rule of Benedict, which, after the Carolingian monastic reform in the ninth century, came to dominate Western monasticism.