原書：2022年9月・日本評論社（2023年度 日経・経済図書文化賞）The book offers fresh new ideas for resolving intergenerational conflicts through the exploration of an entirely new field, conceptualized in philosophy, developed in economics, and tested in experiments. In particular, this work develops the theory of intergenerational cooperation based on a new relationship of direct reciprocity between generations. The original Japanese edition of this book was awarded the 66th Nikkei Prize for Excellent Books in Economic Science.