Esposito then looks in more detail at Islamic theology, law, and practice. Medieval theological conflicts centred on the relationship of faith to works, the status of grave sinners, and the relationship between the absolute power of God and human free will; a key figure was the tenth century synthesiser al-Ashari, whose followers became the dominant school of Sunni theology. The sources of Islamic law are the Quran, the Sunna of the Prophet (Muhammad's deeds as a normative model), analogical reasoning, and the consensus of the community. The five pillars of Islam are the profession of faith, prayer, almsgiving, the Ramadan fast, and the Hajj or pilgrimage to Mecca. Different schools of law handle other areas in different ways: Esposito touches on family law (divorce and inheritance), the relationship between customary practice and Quranic prescription (in rules about veiling and seclusion), Sufism, and Shii differences.
Premodern revivalist movements (such as the Wahhabi movement in Arabia, the Sanusi and Mahdi movements in north Africa, and Shaykh Ahmad Sirhindi and Shah Wali Allah in India) attempted "to reclaim and implement authentic teachings of the Quran and Sunna". In contrast modernist movements (led by men such as Jamal al-Din al-Afghani, Muhammad Abduh and Rashid Rida, and Sayyid Ahmad Khan and Muhammad Iqbal in India) "felt free to suggest that many practices acceptable in the past were no longer relevant", claiming "the right and necessity to formulate new regulations" and advocating "an adaptation of Islam to the changing conditions of modern society". And beginning in the first half of the twentieth century, neorevivalist movements such as the Muslim Brotherhood and the Jamaat-i-Islami saw Islam as "a comprehensive ideology for personal and public life, the foundation for Muslim state and society". Meanwhile traditionalists defended the special status of the ulama (religious scholars) and opposed reforms, especially of family law. At the core of differences were debates over ijtihad (rational analysis and interpretation of law).
Whether labelled fundamentalism, political Islam, or revivalism, "the dominant theme of contemporary Islam has been its resurgence". Key elements of this are a belief that religion is integral to politics, law, and society, a return to the original sources of Islam, a call for Islamic law and an Islamic social order, opposition to Western secularism (but acceptance of science and technology), and struggle against corruption and social injustice. More radical activists go beyond these, "believing that theological doctrine and political realism necessitate violent revolution". Esposito illustrates the varying course of Islamic revivalism with thirty pages on particular countries — Egypt, Libya, Iran, Lebanon, Saudi Arabia, and Pakistan — and twenty pages on Islam in Europe and the United States (including African-American Islam).
"[T]he unity of Islam, from its early formation to contemporary developments, has encompassed a diversity of interpretations and expressions of faith". And this diversity will continue, along with conflicts between secularists, conservatives, neotraditionalists, and reformers. Focal issues include modernisation, the status of the ulama and legal reform (especially in the area of women's rights and the status of non-Muslim minorities), and the Islamization of society.
In his preface Esposito writes that his goal is "to enable readers to understand and appreciate what Muslims believe and practice". With its primarily historical approach, The Straight Path only partially succeeds in this — to give a feel for the role Islam plays in the lives of (particular) believers requires, I feel, more local and personal perspectives, perhaps ethnographic or fictional. As history, however, The Straight Path works well, giving a good feel for Islam's historical depth and geographical reach. My one major complaint here is that it has almost nothing about Indonesia and Malaysia and the Philippines, about Islam's distinctive path in Southeast Asia. In contrast its coverage of Islam in the West is unusually extensive, with Esposito treating this as a major topic in its own right and not just as an afterthought.