Berkey is an Associate Professor of History at Davidson College. He describes Islam as having developed across generations, and he writes of various religious traditions having had an influence on Islam. "The story of Muhammad ascending to heaven and meeting God, for example, has parallels in both Zoroastrian and Manichaean texts." And, of course, there is Islam's adoption of elements of Christianity and Judaism – obvious to any scholar familiar with the Koran.
Berkey mentions the rise of towns and a mercantile economy as having had an impact on religious developments, including Christianity and Islam. He writes:
[T]he existence of regional and trans-regional trading networks discouraged cultural and religious parochialism. They helped to make possible, for example, the emergence of traditions which claimed adherents beyond any one city or locality.
Berkey states that Islam was originally a monotheism for Arabs and that later, following Arab conquests outside of Arabia, Islam became a faith for others – as it was for Christianity, which was a movement of Jews and developed into a faith that included others. This is what academics call a universalist faith.
Berkey writes of a connection between monotheism and its inclination toward universalist faith. He writes:
Polytheistic religious systems by their very nature acknowledge a multiplicity of paths to truth, or salvation, or whatever is the goal of the religious enterprise. The belief in a single god, by contrast, can easily become an assertion that that deity can be understood and approached in only one way.
Monotheistic conquerors do not adopt the gods of those they conquered into their pantheon of gods; they have no pantheon of gods. But Berkey describes Islam as a universalist religion taking shape during conquests "through a process of dialogue with the other faith traditions." He claims:
... it is misleading to speak of the "appearance" or "rise" of Islam, if those words convey a sense of unproblematic apparition as sudden as that of the Arab warriors before the bewildered Byzantine [Constantinople's] or Sasanian armies. It would be safer to say that Islam "emerged," gradually and uncertainly, over the decades – an "ill-defended period of gestation" – which followed the death of the Prophet Muhammad in 632.
Berkey writes of Islam's sectarianism during the first century and a half after Muhammad's death being helped by Islam's "lack of authoritative institutional structure." There was conflict over what was to be accepted as orthodoxy and what was heresy. Islam's Arabic origins had given it the Arabic language as an orthodoxy, but there was the split between Shia and Sunni identities and memories, and "different views of the nature and locus of religious authority." Central to the Sunni view of history "was the idea that the community as a whole had got things right, that at least in broad outlines it was following the will of God. They find support for this view in the statement attributed to the Prophet that "my community will never agree upon an error." The Muslim community, as the Sunnis see it, accepted Abu Bakr as the first caliph who followed the Prophet, therefore Bakr was right as the Prophet's successor. The Shia, on the other hand, "insisted that the Prophet, as the bearer of God's guidance," had named Ali ibn Abi Talib as "the divinely-inspired Imam who was to follow him."
As for the creation of Islamic Law – the Sharia – Berkey writes that it "began as a disparate and ad hoc system." There was, he writes, "...considerable diversity ... both because Muslims in different regions developed different responses to the particular problems they faced, and also because the law as applied was derived from a variety of sources, some formulated by pre-Muslim communities." Gradually, according to Berkey, " a more precisely delineated system emerged." The formation of Islamic law, he adds, was "a critical step in the consolidation of a unifying if not entirely uniform Muslim identity."
Intellectuality and interpretation – what Berkey calls religious knowledge ('ilm) – was a part of the development of Islam. He writes:
This knowledge was embedded in the rich and inter-related body of texts – principally the Koran, collections of hadith, legal treaties and textbooks and commentaries on them – which formed the substantive basis for the training of those scholars who were known as the ulama.
Berkey writes of the mystical tradition which came to be known as Sufism, which came into conflict with Muslim political authorities of some ulama. Berkey writes:
Sufis themselves have traced, with sincere conviction, the intellectual descent of their principles and ideas back to the very earliest Muslims, including most importantly Ali ibn Abi Talib and the Prophet Muhammad himself. That claim is certainly a pious fiction, but the Koran does contain a number of verses that can legitimately be read as expressing support for certain principles, such as asceticism, which came to be hallmarks of the Sufi tradition.
The last of Berkey's twenty-six chapters is titled "Popular Religion," dealing with Islam deriving from "inspiration and legitimacy" from the Muslim masses – rather than from the ulama who are recognized as having "the informal but critical" authority of establishing the parameters of what constitutes Islam. "Hostility to innovation has been a long-standing element of Islamic discourse," writes Berkey. But there have been influences from outside of Islam, such as a Persian celebration of the New Year, which, according to Berkey,
... became popular among Muslims and Christians in Syria, Egypt and elsewhere over the course of late antiquity and the medieval period. Its popularity no doubt stemmed from the practices associated with it ... practices reminiscent of the Saturnalia of antiquity and the carnivals of medieval and early modern Europe...
There was also common Muslim individuals turning to saintly characters or holy men "for intercession and mediation, both with God and with established authorities." Writes Berkey:
Despite some Koranic verses which seemed to reject the possibility (for example, 2.48), the anticipation that pious individuals might successfully plead with God on behalf of another became a ubiquitous feature of medieval Muslim piety.
Rather than consult with recognized authority figures, Muslim individuals were inclined to speak with persons deemed holy by their asceticism about their worldly concerns, such as slaves that had fled, or the complaint that a master was unjust, forcing the holy men, "who had quit the world," back to worldly concerns.
Berkey's divides his 286-page book into four parts, which, with his chapters, are:
Part I. The Near East before Islam
2. The religions of late antiquity
3. Arabia before Islam
4. The early seventh century
Part II. The Emergence of Islam, 600-750
5. Approaches and problems
6. The origins of the Muslim community
7. Early Islam in the Near East
8. The Umayyad period
9. The beginnings of sectarianism
10. The non-Muslims of early Islam
11. The 'Abbasid revolution'
Part III. The Consolidation of Islam, 750-1000
12. Issues of Islamic identity
13. Religion and politics
15. The formation of Sunni traditionalism
16. Asceticism and mysticism
17. The non-Muslim communities
Part IV. Medieval Islam, 1000-1500
18. The medieval Islamic Near East
19. Characteristics of the medieval Islamic world
20. A Sunni 'revival'?
21. Common patterns in social and political organization
22. Modes of justice
23. The transmission of religious knowledge
25. Popular religion
26. From medieval to modern Islam