Bernard Lewis began his research career with the study of medieval Arab, especially Syrian, history. His first article, dedicated to professional guilds of medieval Islam, had been widely regarded as the most authoritative work on the subject for about thirty years.

However, after the establishment of the State of Israel in 1948, Arab countries no longer admitted scholars of Jewish origin to conduct archival and field research there. Therefore, Lewis switched to the study of the Ottoman Empire, while continuing to research Arab history through the Ottoman archives, which had only recently been opened to Western researchers. A series of articles that Lewis published over the next several years revolutionized the history of the Middle East by giving a broad picture of the Islamic society, including its government, economy, and demographics.

Contrary to the position that the backwardness of Muslim lands is a result of Western colonialism, Lewis argues that the decline of the Ottoman Empire and other Muslim countries was largely self-inflicted. Their failure to keep up with the West stemmed from their cultural arrogance, which was a barrier to creative borrowing. Lewis analyzes the causes and consequences of the Muslim inflexibility in his work Muslim Discovery of Europe (1982).

Revulsed at the Soviet and Arab attempts to delegitimize Israel as a racist country, Lewis wrote a study of anti-Semitism Semites and Anti-Semites (1986).

In addition to his scholarly works, Lewis wrote several influential books accessible to the general public: The Arabs in History (1950), The Middle East and the West (1964), and The Middle East (1995). In the wake of the September 11, 2001 attacks, the interest in Lewis's work surged, especially his 1990 essay The Roots of Muslim Rage. Two of his books were published after 9/11: What Went Wrong? (written before the attacks) and The Crisis of Islam.

Views and influence on contemporary politics

In the mid-1960s, Lewis emerged as a commentator on the issues of the modern Middle East, and his analysis of Arab-Israeli conflict and the rise of militant Islam brought him publicity and aroused significant controversy. Lewis's policy advice has particular weight thanks to his scholarly authority. U.S. Vice President Dick Cheney remarked: "...in this new century, his wisdom is sought daily by policymakers, diplomats, fellow academics, and the news media."

A harsh critic of the Soviet Union, Lewis continues the liberal tradition in Islamic historical studies. Although his early Marxist views had a bearing on his first book The Origins of Ismailism, Lewis subsequently discarded Marxism. His later works are a reaction against the left-wing current of Third-worldism, which came to exercise significant influence over Middle Eastern studies.

Lewis advocates closer Western ties with Israel and Turkey, which he saw especially important in light of the extension of the Soviet influence in the Middle East. Modern Turkey holds a special place in Lewis's view of the region due to the country's efforts to become a part of the West.

Lewis views Christendom and Islam as civilizations that have been in perpetual collision ever since the advent of Islam in the 7th century. In a seminal essay The Roots of Muslim Rage (1990), he saw the struggle between the West and Islam gathering strength. It was in that essay that he coined the phrase "clash of civilizations", which received prominence in the eponymous book by Samuel Huntington.

In 1998, Lewis read in a London-based Arabic newspaper Al-Quds Al-Arabi a declaration of war on the United States by Osama bin Laden, a person of whom Lewis had never heard before. Recognizing in bin Laden's language the ideology of jihad, Lewis wrote an essay A License to Kill in which he warned about the danger presented by the holy warrior.

Criticism and controversies