Tomáš Glomb uses digital and mathematical models to bring clarity to the study of the spread of the Isiac cults (the worship of Isis, Serapis, Anubis, Harpocrates and a small number of other Egyptian gods) in the Hellenistic Mediterranean. His short book covers the development and spread of the cults before focusing on two case studies and ending with a final summary chapter. The first case study explores the spread of the cults in the Aegean. Glomb creates a visual model mapping the likely trade routes taken between ports in the Aegean and Egypt (a major source of grain for the region), as well as a mathematical model which shows how various elements might have impacted the spread of the cult. According to these models, military and diplomatic interventions by the Ptolemies indirectly led to their spread. In the second case study, focused on the coast of Asia Minor, Glomb maps out the distances between major cities, Ptolemaic political centres and the locations of Isiac temples or artefacts using a sophisticated system that takes into account average journey times. Through this, he demonstrates that cities under Ptolemaic rule or influence (or close to one) were more likely to have an Isiac temple within their limits or close by. A spatial visual analysis demonstrates that coastal cities with high levels of traffic from Egypt were more likely to have evidence of Isiac cults than inland cities. He concludes that the Ptolemies had a positive role in the spread of the Isiac cults, but the model cannot confirm whether this was the result of official encouragement.

Glomb is clear about what the mathematical models can and cannot show, and his conclusions are always well balanced. One wonders how different the findings gained through this mathematical methodology are from the results of standard historiographical methodologies. For example, the importance of trade routes in the spread of religious ideas is long established. In his article ‘Two Studies on the Cult of Serapis in the Hellenistic World’, Opuscula Athreienisia, 3 (1960), P.M. Fraser had already arrived at very similar conclusions, although Glomb’s methods provide new insights into the underlying causes of this trend. I would compare this book to Laurent Bricault’s recent Isis Pelagia (Leiden 2020), which focuses on one specific aspect of the goddess, her maritime form. Bricault takes it as a given that the sea was a major vector for transmission of this cult. But he follows this up with an examination of how the cult developed on both the global and the local level through a sustained analysis of the evidence, looking at the roles played by private and state actors, like the Ptolemies. While acknowledging the complexity of the situation, the book’s conclusions are somewhat lacking in depth. For example, in the final chapter summarizing the findings, Glomb argues that the spread can be explained in part by the fact that the Ptolemies ‘occupied the transportation network in the Aegean Sea by capturing very connective nodes’ (137). But what did this look like in practice? Who were the sailors, the dock workers, the ship-owners and merchants who made up this transportation network? How did they engage with Ptolemaic officials and how and why did this benefit the spread of the Isiac cults?

A reader’s appraisal of how successful Glomb is in his approach will come down to the extent to which they believe mathematical modelling has a role in the study of ancient history. Glomb himself argues that a ‘methodological synthesis between quantitatively oriented approaches and established tools of historiography’ (140) would benefit the discipline. A more critical approach to the evidence would have been desirable. For example, the accidence of survival and differences in reading need addressing when creating quantitative models based on ancient ‘data sets’ such as epigraphy. Mathematical methodologies offer a strong starting point, providing new readings and highlighting trends that need further investigation, but they cannot wholly answer more nuanced questions.

Those caveats aside, it is a useful addition to scholarship on the Isiac cults and more generally on Hellenistic religion. Despite using advanced mathematics, it is an accessible book. Glomb takes us through the mathematical process and findings in a very clear and engaging style. This makes it possible for a competent scholar to understand and pick apart the workings, even if they would not be confident to use and manipulate the actual formulae. This is vital to ensure the book can be understood more widely. Overall, it is a very readable study that holds value across ancient history more generally as it provides a sustained practical demonstration of how statistical modelling can be applied to historical problems. I would recommend it to anyone interested in new ways of practising history.