The world’s 1.6 billion Muslims are united in their belief in God and the Prophet Muhammad and are bound together by such religious practices as fasting during the holy month of Ramadan and almsgiving to assist people in need. But they have widely differing views about many other aspects of their faith, including how important religion is to their lives, who counts as a Muslim and what practices are acceptable in Islam, according to a worldwide survey by the Pew Research Center’s Forum on Religion & Public Life.

The survey, which involved more than 38,000 face-to-face interviews in over 80 languages, finds that in addition to the widespread conviction that there is only one God and that Muhammad is His Prophet, large percentages of Muslims around the world share other articles of faith, including belief in angels, heaven, hell and fate (or predestination). While there is broad agreement on the core tenets of Islam, however, Muslims across the 39 countries and territories surveyed differ significantly in their levels of religious commitment, openness to multiple interpretations of their faith and acceptance of various sects and movements.

The survey asked Muslims whether they identify with various branches of Islam and about their attitudes toward other branches or subgroups. While these sectarian differences are important in some countries, the survey suggests that many Muslims around the world either do not know or do not care about them.

Muslims in the Middle East and North Africa tend to be most keenly aware of the distinction between the two main branches of Islam, Sunni and Shia. In most countries surveyed in the region, at least 40% of Sunnis do not accept Shias as fellow Muslims. In many cases, even greater percentages do not believe that some practices common among Shias (or among fellow Sunnis such as Sufis and Barelvis), such as visiting the shrines of saints, are acceptable as part of Islamic tradition. Only in Lebanon and Iraq – nations where sizable populations of Sunnis and Shias live side by side – do large majorities of Sunnis recognize Shias as fellow Muslims and accept their distinctive practices as part of Islam.

Opinion also varies as to whether Sufis – members of religious orders who emphasize the mystical dimensions of Islam – belong to the Islamic faith. In South Asia, Sufis are widely seen as Muslims, while in other regions they tend to be less well known or not widely accepted as part of the Islamic tradition. Views differ, too, with regard to certain practices traditionally associated with particular Sufi orders. For example, reciting poetry or singing in praise of God is generally accepted in most of the countries where the question was asked. But only in Turkey do a majority of Muslims believe that devotional dancing is an acceptable form of worship, likely reflecting the historical prominence of the Mevlevi or “whirling dervish” Sufi order in Turkey.

Sunni Muslims and Shia Muslims (also known as Shiites) comprise the two main branches of Islam. Sunni and Shia identities first formed soon after the death of the Prophet Muhammad in 632 C.E., centering on a dispute over leadership succession. Over time, however, the political divide between the two groups broadened to include theological distinctions and differences in religious practices as well.

While the two groups are similar in many ways, they differ over conceptions of religious authority and interpretation as well as the role of the Prophet Muhammad’s descendants, among other issues. (Shias in particular follow the spiritual line of Prophet Muhammad and the 12 Imams in his family and descendants.)

Members of Sufi orders, which embrace mystical practices, can fall within either the Sunni or the Shia tradition. In some cases, Sufis may accept teachings from both traditions.

The survey also asked about attitudes toward Sufis and members of regionally specific groups or movements. Views of Sufis vary greatly by region. In South Asia, for example, a median of 77% consider Sufis to be Muslims; half in the Middle East and North Africa concur. However, significantly fewer Muslims in other regions surveyed accept Sufis as members of the Islamic faith. For example, in Southern and Eastern Europe (Russia and the Balkans), a median of 32% recognize Sufis as fellow Muslims, while in Southeast Asia and Central Asia the comparable figures are 24% and 18%.

Especially in Central Asia, the low percentage that accepts Sufis as Muslims may be linked to a lack of knowledge about this mystical branch of Islam: majorities in most Central Asian countries surveyed say either that they have never heard of Sufis or that they do not have an opinion about whether Sufis are Muslims.

Views of regionally or locally based groups and movements are mixed. For example, small percentages in Malaysia and Indonesia (9% and 5%, respectively) say that members of the mystical Aliran Kepercayaan movement are Muslims.

In Turkey, most Muslims (69%) acknowledge Alevis, who are part of the Shia tradition, as fellow Muslims. Meanwhile, in Lebanon, a modest majority (57%) say members of the Alawite sect are Muslims. By comparison, only about four-in-ten Lebanese Muslims (39%) say the same about the Druze.

(The anti-Sufi views within Muslims are generally more prevalent within Salafi and Wahhabi (the ultra-orthodox puritanical) groups within Islam. In recent decades, such Takfiri- or extremist ideology against fellow Muslims has been spread through Islamist groups, publications, mosques and seminaries funded by the Saudi, Emirati or Qatari petrodollars.)

Source: Adapted with some edits and additions from Pew