Fowden begins by arguing for the central importance of the Fertile Crescent in the long struggle between Rome and Iran. He defines control of the Crescent as necessary for "world-empire" and argues that this requires control of both the Iranian plateau and the eastern Mediterranean coastline, thus denying the accolade to both the Roman and Sasanian empires; according to Fowden, Cyrus created the first "political world-empire" and the next was the Islamic Caliphate, which was also a "cultural world-empire". The creation of such a general scheme from so few instances seems strained to me, especially in the absence of any comparison at all with other "world-empires" in India or China. More convincing is his stress on the role of religious and cultural universalisms in the conflict between Rome and Iran.
Chapter two is a survey of universalist trends in pagan Rome: the imperial cult, the claims of Rome and Alexandria to be religious centres of more than parochial status, Aurelian's cult of Sol, and Julian and Mithras. This leads in chapter four into a study of Constantine and his empire-building ambitions (especially those aimed at Iran). Here, though he does include some caveats, Fowden somewhat uncritically follows Eusebius in an account of Constantine as a "universal crusader"; his comparison of Constantine with Ashoka is more rewarding. In both these chapters I felt the absence of any kind of sociological perspective on Roman religion; Fowden stays at the level of literary texts and the motivations of leaders, making no attempt to explore the social processes involved in the spread of universalist ideas.
In chapter three Fowden describes four examples of "religions of real or imagined universal appeal" in the Fertile Crescent — the Sabians of Harran, Judaism, Manichaeism, and Christianity —, claiming that "each represents a phase in the evolution of late antique universalism". The exact nature of the evolutionary progression implied is not clear, however, since the ordering is hardly chronological. (Based on judgements such as "Zoroastrianism presented an ethical advance on Indo-Iranian polytheism" and on the almost devotional epilogue, my guess is that Fowden is himself a Christian, but this is nowhere stated.) This chapter also illustrates Fowden's habit of offering broad, sweeping statements without any attempt at justification: "Manichaeism was a typically appealing and dynamic product of the Fertile Crescent's pluralist environment... a characteristic example of the sort of universalism which grows up between political and cultural blocs" (are there really enough universalising religions to warrant this sort of generalisation?); and "identification with a dynamic, expanding state is essential to the dissemination of a universal religion" (but Christianity was a success before Constantine).
The chapter of Empire and Commonwealth which I liked most focuses on the string of Christian (largely Monophysite) states running along the border with Iran, from Ethiopia in the south to the Caucasus in the north (with the most enduring being at these extremities). Fowden sees these states, together with other non-Chalcedonian Christians within the Empire and Nestorian communities "behind enemy lines" in Iran, as a "First Byzantine Commonwealth" defined by shared historical experiences. Refraining from tempting oversimplifications, he presents an brief outline of the complex forces responsible for their creation and continuation. The variety of the heresies which beset Orthodox Christianity in late antiquity has always intrigued me, and I found that Fowden's account made the history of the period much more comprehensible.
In the final chapter Fowden argues that Islam, in its successful combination of a monotheistic religious universalism with "world-empire", should be seen as the culmination of trends already present in late antiquity rather than as an external, destructive force. He devotes most of the chapter, however, to analysis of examples from early Islamic art, architecture, and coinage. This emphasis has no counterpart in the earlier chapters and the only hint of a motivation for it is a statement that "we have little unfiltered evidence of any sort from the first century after the hijra". To me it suggests that Fowden is less at home with Islam and Arabic history than he is with Christianity and Roman history. (Ibn-Ishaq and Al-Tabari are only mentioned in passing, in such a way that the reader might think they were most important for their choice of residence or their influence on art!) The chapter concludes with an account of the religious history of the Caliphate and its breakup to form the Islamic Commonwealth.
Looking back at this review I realise it seems almost unmitigatedly negative. This is not actually how I felt about Empire and Commonwealth. Whatever my misgivings about Fowden's attempts to formulate big generalisations, he never pushes them to the point of tendentiousness. More importantly, his account maintains a level of excitement commensurate with the intrinsic appeal of its subject; it will appeal to interested amateurs as well as to specialists.