Islam is the predominant religion in the Middle East and is the second-largest religion in the world. Not limited to the Middle East, it has approximately 1.4 billion members, 80% of which are non-Arabs. It is one of the fastest growing religions in the world. Its adherents are called "Muslims" (also spelled Moslem), historically "Musselman", "Muhammedans", or even simply "Turks" in Europe and North America. In Arabic, a Muslim is "one who submits to God". Allah is simply the word God in Arabic.
Muslims, like Jews and Christians, are monotheistic and trace their roots to Abraham. However, they receive their instruction from the Qur'an (also spelled Koran). Islam's beginnings can be traced back to the 7th century under the leadership of Muhammad and his followers. Islam is largely based on pre-existing Arabian paganism, Jewish, Christian and Zoroastrian influences.   The vast majority of Muslims also consider haddith literature, the traditional teachings and sayings of Muhammad, as secondary religious scripture.
An universalizing (evangelizing) religion, it spread throughout the world by military conquest and Muslim missionaries. The moral and legal code of Islam is called Sharia law, which has received widespread criticism for its anachronistic and unjust laws and barbaric punishments.
Five pillars of Islam
There are five principles that are generally considered mandatory practices by Muslims:
- There is only one god Allah. Muhammad is his (greatest and final) messenger/prophet.
- Prayer five times a day, facing in the direction of Mecca.
- Tithing, including 2.5% of capital assets.
- Fasting and holiness during the holy month of Ramadan.
- Pilgrimage to Mecca at least once, if possible.
The main sects within Islam are Sunni (~80% of Muslims) and Shia (10-20%). The two denominations grew out of a split over who was to succeed leadership after Muhammad.  There are several minority branches outside mainstream Islam, including:
Other movements within Islam:
- The Salafi movement is a traditionalist sect and sometimes considered part of Sunni Islam.
- Quranism, rejects the authority of hadith.
- Wahhabi, an traditionalist variant of Sunni Islam. It has largely been incorporated into Salafism but was perhaps the first Salafist movement in the modern era.
- Main Article: Sharia law
Sharia law is based upon a literal interpretation of the Qur'an and the hadith; being extrapolated upon where required by Fiqh - which is Islamic jurisprudence. The extrapolations may vary depending on the sect and the school of thought followed by different scholars, however the core laws of Sharia remain the same across the different schools of fiqh and the sects. Sharia law is widely criticised for containing unjust laws and mandating cruel punishments.
Islamic fundamentalism is fairly strong in middle-eastern regions, one result being the oppression of women. Spurred by, though unlikely exclusively due to, inflammatory passages of the Qur'an, there have been instances of terrorism in the name of Islam, including suicide bombings, beheadings and public stonings. Many Muslim fundamentalists adhere to a traditionalist Salafi interpretation of Islam. Some terrorist organizations follow or promote an extreme version of Salafi Islam.
Moderate Muslims are more prevalent in Europe. However, there are still a minority of extremists who campaign and protest with the intent of silencing criticism of Islam and Muhammed. The protection of religion from criticism, sometimes referred to as "religious defamation", is incompatible with liberal norms such as freedom of speech.
Islam is often called a "religion of peace" but the Qur'an contains many violent quotations.  Most contemporary Muslims believe there is no religious obligation to use force to spread Islam. In 2011, a Gallup poll found that 78% of American Muslims believe that violence that kills civilians is never justified. This makes Muslims less bloodthirsty than Christians (38%-39%) or atheists (56%). 
False association with terrorism
Muslims are often accused of being potential terrorists by certain media and political sources. This is questionable because the vast majority of Muslims are non-violent, particularly within stable societies. This implies terrorism is instead a result of social and political circumstances. Writers such as Sam Harris have argued that there are some Islamic concepts, such as jihād and martyrdom are helpful concepts for terrorist groups to legitimise their tactics; however it is important to realise that any ideological system can have an extremist or violent interpretation.
The false association of Muslims and terrorism also overlooks the stronger association between Christianity and terror.  Ideologically motivated Christians that use force to achieve political or social aims are routinely called "criminals" rather than "terrorists", even though a Muslim who performed the same acts would be branded a terrorist. In recent years, more terrorist attacks in the US have been by religiously motivated Christians rather than Muslims. 
There are some traditional Islamic practices that are not clearly or explicitly specified in Sharia law but are still characteristic of Islam.
Islam has traditionally encouraged women to wear head coverings, such as a Hijab. Young girls are excluded from this practice. Sharia law states that people should dress modestly but is unclear as that what is required for modesty.  Adoption of this practice is largely influenced by culture, with some cultures imposing pressure not to wear the headscarf. The Turkish government has banned headscarves in public office or at universities. 
More fundamentalist interpretations of Islam practice gender segregation for non-relatives.
Possible incompatibility with an open society
Islam was conceived as a system that governs both spiritual and Earthly matters. It has a number of practices that function as a state, including taxation and a legal code. Some observers argue that this makes Islam incompatible with the separation of church and state. This is one of the core principles of an open society. A state having an official religion tends to alienate those who do not agree with this view. Also, the established religion often undermines other aspects of an open society, such as democracy, separation of legislature and judiciary, introducing religious tests, etc.
- "[...] Islam, perhaps more than other monotheistic religions, invites itself into every aspect of social life. More specifically, Islam is inherently and by definition inconsistent with the separation of church and state. "
- "The most difficult part of Islamic Law for most westerners to grasp is that there is no separation of church and state. The religion of Islam and the government are one. Islamic Law is controlled, ruled and regulated by the Islamic religion. The theocracy controls all public and private matters. Government, law and religion are one. "
- "Even though ideologically [in Islam] there can be no separation between church and state, both Sunnis and Shiites developed a separation very early on. In the Sunni world, the separation was de facto; Islamic law developed as kind of a counterculture to the aristocratic courts. In the Shiite world, there was a separation of church and state on principle. It was held that since every state was corrupt, clerics should take no part in them, that the religious should withdraw until the messiah came and established a proper Muslim state. "
Compromise is necessary in democracies, particularly when drafting laws. It is difficult to achieve a consensus when one party believes they have an objectively perfect legal system. Islam also does not recognize equality under the law, as different laws apply depending on a person's religious beliefs.
Islam has a strong tradition of fatalism which arguably stifles human initiative.
- "Human agency and human freedom are nullified. [...] Why should human effort strive by sanitary means to prevent disease, when death or life depends in no way on such measures but upon the will of Allah? "
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- ↑ CNN, Harris: Islam is "mother lode" of bad ideas, 13 Oct 2014
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- ↑ Just a few of many violent quotes from the Qur'an
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- Islam on Faith in the Holy Land Series on Israel's Youtube channel
- The myth of Islamophobia
- The religion of fear
- Appeasing Islam
- Islam is not a victim