Abstract
The third lecture takes as its starting point situations of failure or destruction of harvests, to observe how this type of event fits into an economy of human relations with God and with nature. Typical stories from the early Middle Ages explain these losses by the intervention of " escamoteurs " or " nefs de nuages " carrying away the harvest. They demonstrate the existence of a " economy " of bad weather, rationalizing losses through the metaphor of market exchange. The Christian economy extends the value of these transactions through the introduction of compulsory tithing, by which humans globally discharge their " natural " debt to the Creator.
