In a ceremonial exchange system, a gift may create an obligation to respond later even when no repayment date is fixed. Valuable objects circulate among households and can signal generosity, alliance, or rank. Market purchases also occur in the same communities, and people sometimes convert cash earnings into ceremonial goods. The categories are therefore not sealed worlds: a gift can carry economic value while its social meaning differs from an immediate sale. The passage warns against assuming either that gifts are purely altruistic or that they are merely disguised purchases.