Gerring, Apfeld, Wig & Tollefsen's admirable work makes a convincing theoretical and empirical case for a simple finding: areas close to harbours are more democratic. While many works on democracy focus on proximal factors, this one looks to the distal, and does not hesitate in leaping back and forth between the ancient and modern. In scope, the work has echoes of Mahan, but there is no simple determinism in this work. Indeed, readers are told not to look for single causal factors in the social sciences, as '[t]here ain't no such thing' (p. 376). This work falls into the ‘environmental possibilism’ category, and the authors are at pains to make clear that their theory cannot explain everything. The work has the potential to cause lively debate among historians. One reason for this is recognised by the authors themselves: dependence on secondary sources. But the authors do something which few historians yet do: use geospatial information as their data. This is the clear value-added of the work, which fleshes out the bones of the ambitious theory. This does mean there are some notable gear shifts between the chapters: Chapter 5 gives a whirlwind survey of the history of harbours and political developments in Europe, North Eurasia, MENA, Africa and Asia, while Chapter 6 runs regression analyses of the PRIO-GRID. As such, this formidable work is not for the faint-hearted. But this is a hugely rewarding read, and one which leaves the reader looking forward to potential future work alluded to in the epilogue: the link between democracy and connectedness.