This dissertation helps explain how and why agriculture escaped its Malthusian structures through the practices of the ecclesiastical proprietors that owned the most productive land around Paris in late ancien régime France. It shows how a confluence of agricultural, social, religious, intellectual, and political factors enabled and encouraged clerics, armed with unique corporate advantages, to build a partnership with tenants that was among the most dynamic in the late ancien régime economy. This matters because it gives a hitherto unrecognized “religious” agronomic and Enlightenment dimension to the French path to modernity.,Untangling the modes, causes, and results of church landlords' practices requires a combination of economic, rural, material, business, political, intellectual, and religious history, using both quantitative and cultural evidence. This dissertation shows how church landlords reinvested far more of their agricultural rents than secular landlords did, and that their reinvestment went into rent relief and into physical infrastructure to enhance tenants’ profits by lowering costs and increasing sales. These supports gave tenants an opportunity to increase output and productivity by building up capital and changing their operations, as well as the incentive to innovate to pay the higher rents that church landlords demanded for their investment. Church landlords’ investment in agriculture was routine, structured, comprehensive, and (in some cases) institutionalized, which explains its success. The landowning clergy’s success in generating agricultural growth through investment in part arose through the immersion of key clerics in Enlightenment institutions and projects, but it also derived from church landlords’ organizational capacity as corporations. Seen as economic "firms," these church corporations were sufficiently permeable that their interests aligned with those of their tenants, though without losing control of decision-making. Church landowners’ investment in agriculture was successful and sustainable because it was informed, and church landlords’ ability to innovate to meet changing organizational needs, and their effect on agricultural growth, demonstrate that this distinctively French, corporate, and ecclesiastical economic model provided a path to modernization that was likely to have remained competitive in the post-revolutionary world. ,This dissertation further shows that church landlords’ investment practices were structured by a politically enforced lack of alternative investment opportunities and by Enlightenment anticlericalism and new ideals of good proprietorship that church landlords turned to their advantage by presenting themselves as model citizens. That strategy protected church landlords’ privileges from criticism by the intellectual elite and the Crown; it meant church landlords felt confident of leading the regeneration of France; and it indicates that agricultural development allowed an emergent utilitarian element within the church to demonstrate its value to society. ,In summary, this dissertation places a large part of that supposedly archaic and declining institution, the church, at the center of the most dynamic elements of contemporary France, in fields with which the church has been associated as an opponent or obstacle, such as the Enlightenment, economic growth, and political change. In doing so, it connects Enlightenment anticlericalism, economic thought, and agronomy to economic change in ways that have been improperly understood until now. Religion in the form of theology is absent from this dissertation, as it is absent from church landlord sources on managing and protecting agricultural wealth. Church landlords’ intervention as agricultural developers arose from their immersion in the Agricultural Enlightenment and in the social, political, and scientific elite. Yet church proprietors’ strategy and role in rural investment were inherently religious: they sprang from the organizational character and capacity of church corporations, and they defended church proprietors against anticlerical criticism in late Enlightenment France. By adopting a broader viewpoint of both religion and the Enlightenment that reflects how both were lived by eighteenth-century clerics, we see that these institutions were in fact strongly interlinked in ways that led to France escaping its agricultural ancien régime.