This is a collection of twenty-nine of Sahas's articles, one in Greek and the rest in English, most of which were published between 1980 and 1995. They are grouped around four themes: the mutual influence of eastern Christianity and Islam; the fall of the Byzantine Levant; the writings of John of Damascus (the subject of Sahas's 1972 monograph); and later Byzantine descriptions of Islam and Muslims, ranging from George Dekapolites to Gregory Palamas (d. 1360). The articles include several useful translations.

Throughout these essays, Sahas wrestles with the proximity and mutual influence of Byzantium and the caliphate, and their religions, at the same time as prominent Christian and Muslim thinkers engaged in polemic and states engaged in warfare. As Nicholas Mystikos (d. 925) put it: ‘there are two lordships, that of the Saracens and that of the Romans, that stand above all others on earth … they ought to be in contact and brotherhood and not, because we differ in our ways of life, habits and religion … alien in all ways to each other’ (p. 5).

Mystikos wrote in a diplomatic capacity, aiming to redeem war-captives, and other writers could take a much more hostile attitude. Some used accumulated ethnic prejudices to dismiss Muslims as Saracens, Achaemenids, Assyrians or Amalekites. Nevertheless, as Sahas notes, it is fascinating that even as Palamas condemns Muslims, he qualifies Islam as a theosebeia, a reverence for the divine, and he differentiates between the essence of Islam and the conduct of Muslims (pp. 10–11).

Many of the essays in the first part of the book identify shared practices and ideas across religious boundaries. Both the Quran and the divine Logos pre-exist creation (p. 55). Monasticism, and the Christian ascetic ethos, is viewed positively and monastic practice influences the five daily prayers, fasting and abstinence from wine (p. 89). The miracles attributed to Muhammad are modelled on those of the Gospels (p. 79). Byzantine Hesychasm and Muslim Sufism share common ideas and practices (p. 109). Christian descriptions of the attributes of God may influence the names of God in the Muslim tradition (p. 324). The naming of the caliph in the khutba may be influenced by the naming of the bishop in the diptychs (p. 129).

Sahas does not so much chart individual moments of reception as observe parallel developments. But, taken together, these cases offer a salutary reminder that ‘Islam’ and ‘Christianity’ are not mutually exclusive systems, but have frequently intertwined and informed one another's development. These essays anticipate recent work in Islamic Studies that has stressed the ability of non-Muslims to influence the evolution of Islam, even when they ask critical or polemical questions.

However, the articles in the collection have not been updated since their original publication. In several cases they have been superseded by more recent literature: the work of Phil Booth on Maximus the Confessor and Sophronius; that of Tom Sizgorich on Christian and Muslim asceticism and violence; that of Fergus Millar, Greg Fisher and Peter Webb on the Arabs; James Howard-Johnston on the wars of the early seventh century and the many works of Sidney Griffith, David Thomas and their students on John of Damascus and on Christian-Muslim relations more generally. Of course, Sahas cannot be faulted for this boom in scholarship, but I thought that these later developments could have stimulated a re-thinking of older ideas, or at least the selection of articles for reprinting. After all, as Sahas notes in his introduction, online repositories make finding older articles much easier, especially for articles such as these that are long clear of any embargo. In the absence of rewriting, I was unsure what the purpose was in simply reprinting the articles.

In a number of cases I reacted very strongly to Sahas's ethnic essentialism. We are told that that John of Damascus was ‘an Arab intellectual’ (p. 350), working in ‘an indigenous Semitic tradition’ (p. 356); that John enjoyed such an influence among Muslims because of his Semitic ancestry and Syrian culture’ (p. 377). The idea that ancestry should explain ideas is obviously highly problematic in general terms. But we can add that to describe John as Arabophone does not let us call him an Arab, since, in the eighth century, the term was closely linked to dress and lineage (and often to Muslim religion as well). We can speak of Christian Arabs to describe groups like the Taghlib and the Tanukh, and they caused problems for Muslim jurists who were unsure of where to place them. But I am not aware of any contemporary evidence of John claiming an Arab identity for himself.

There were also several points where Sahas supports ideas that have since been disproved. There is no contemporary evidence that Miaphysites actively supported the Arab conquests (p. 103 n. 17). And in arguing the Heraclius’ experiments with Monotheletism ‘rekindled’ Miaphysitism in Syria (p. 263), Sahas seems to reproduce polemical statements by Theophanes, which ignore Monotheletism's real successes in the seventh century. Historians would be less willing to describe the Christian community as shrinking in the eighth century (p. 332): the tipping point for Christians here probably only came after the First Crusade. The term ‘Syrian Orthodox’, which Sahas uses to describe the Chalcedonian John of Damascus (p. 363), is normally used for Miaphysites (including the modern Syrian Orthodox Church). Likewise, the historian Eutychius of Alexandria was not a Miaphysite, but a Chalcedonian (p. 145, though he is correctly identified at p. 364 n. 32).