Exchange and reciprocity are central concepts in allforms of human society. Based on a system of mutualobligation, they denote any activity in whichvaluables are circulated between individuals orgroups of people. In the religious sphere theyinclude the transfer of both material and immaterialgoods between human and spiritual beings. Asoutlined by Marcel Mauss in his Essai sur ledon, the classic work on the total systemof reciprocity, such exchange is governed by theprinciple of the gift entailing thecounter-gift.