Mr. Robb says that in this work he stumbled on an understanding of how astronomy guided the Celts, semi-nomadic tribes who dominated Europe in the Iron Age, from 800 B.C. to A.D. 600, in their migrations from the Iberian Peninsula to the Black Sea.

The argument is complex — think of it as Asterix meets “Longitude” — but Mr. Robb basically asserts that the Celts followed the directions of their druids, a caste of scholar-priests who believed in following the path of the sun at the solstice to guide their vast tribal migrations. These migrations unfolded before 58 B.C., when Julius Caesar crossed the Alps and defeated the Gauls, a Celtic tribe, effectively ending Celtic civilization.

In their wanderings, Mr. Robb writes, the Celts laid the groundwork for centuries of European history to follow. They built roads and bridges — making it easier for Caesar to take Gaul, Mr. Robb notes — developed complex communications systems, imposed rule of law, traded with the Greeks, carried out a census and even held an annual pan-tribal congress of druids in southern France.

We’re like meridians, all beginning and ending in the same place. We spread out from the beginning and go our separate ways, over seas and mountains and islands and deserts, each telling our own story, as different as they could possibly be. But in the end we all converge and our ends are as much the same as our beginnings.

The surveillance state is a nexus, undergirded by an ideology that sees every person as at least a potential threat and every communication as potentially worth surveilling. This nexus relies on Silicon Valley participation, intensive and expensive spycraft and, crucially, us. We live, always-already, as surveilled subjects as we live online, unwittingly handing over immense amounts of data about our lives, connections and affiliations.