This dissertation explores the development of social engagement for the Carthusian hermit-monks in light of their commitment to solitude. Such involvement took a multitude of forms, including relations with donors, legal actions, involvement with Church governance, letter writing, and finally the establishment of monasteries in urban areas. It makes extensive use of archival sources—especially for La Grande Chartreuse (the Order's first house founded in 1084) and Vauvert, Paris (the first urban house founded in 1257)—to question the accepted narrative of purity and isolation for such medieval religious groups. This narrative likely originated with medieval Carthusians themselves. The present-day Order as well as many scholars have embraced it. An introductory chapter sketches the contours of the question and its neglect. The next three chapters explore images for Carthusian life found in the person of their founder, Bruno, in Guigo's Customary—the Carthusian rule, and in two twelfth-century polemics. Each chapter establishes a narrative that portrays hermit-monks who claimed images of solitude for their lives. At the same time they engaged in a careful set of relationships with other monks as well as with the outside world. Chapter five examines the patterns of Carthusians functioning as bishops, while chapter six considers the problematic election of one Carthusian monk as bishop of Grenoble. These show the existence of networks between episcopal sees and Carthusian houses as well as connections between the monasteries themselves. Chapter seven addresses the ways in which Carthusians used letter writing as a means to cultivate relationships both inside and outside their monasteries. Letters were a means for the monks to be present to one another, to participate in the wide Church and society, and to network, including with the Capetian Royal House. Chapter eight examines patterns of property acquisition at La Grande Chartreuse and at Vauvert, Paris during their first one hundred years. The Carthusians moved to Paris at the invitation of Louis IX, making Vauvert not only the first urban house, but also a royal one—the fruit of their networks and pure image. In each case, Carthusians engaged in varied relationships with donors, even to the extent of eventually altering their way of life. In a variety of ways, this dissertation demonstrates the very real engagement of medieval Carthusians with the world outside their cloisters. In essence, these silent monks found means for balancing their putative solitude with a presence in the City, the larger Church, and the World.