ABSTRACT
Some obligations to future generations have their source in the good people have received from past generations. Reciprocity is justified by reference to its value for sustaining the exchanges necessary for a productive social life. Obligations of reciprocity to contemporaries come from the transactions people have with them. Obligations to future generations come from what they have received from their predecessors. The application of the reciprocity arguments to particular cases is often a difficult business even in face to face transactions. In the case of acting for future generations those problems are magnified, and some general comments on them may be worthwhile. The author shall make his remarks under four headings: Substitutions, savings, increase, and temporal horizons. The obligations of reciprocity are in general ordered by social distance. That is, people who have the reciprocity cluster of virtues tend, as a consequence of those virtues, to resolve conflicts in favor of those closest to them.
