This book has been built on a theoretical scaffolding, with each chapter presenting both a piece of the theory and a test of that part. The flow of the argument has been theoretical and not driven by substantive puzzles as much as by a desire for theoretical elaboration. The central task has been a desire to explain variation between cooperation and noncooperation, for which I used a bottom-up theory of trade policy. Because the central result is that low-tariff countries are more likely to cooperate than high-tariff countries, examining the domestic political reasons for high tariffs has played an important role in the analysis. At the same time, each state's policy conditions the policies of other states, pointing to an analysis of reactions as well as international-level norms such as MFN.

The first half of this chapter summarizes the theoretical claims of the book. Beyond providing a mere summary, I also develop some suggestions for a research agenda on international cooperation. The second half uses this theory to provide a synthetic account of the nineteenth-century trade treaty network, providing an alternative narrative of nineteenth-century trade policy. For those interested in the nineteenth century, it points to greater Germany as central to the regime.