Islamic extremism

Islamic extremism, Islamist extremism or Radical Islam is extremism associated with the religion of Islam. These are controversial terms with varying definitions, ranging from academic understandings to the idea that all ideologies other than Islam have failed and have demonstrated their bankruptcy, as well as political ones like the definition by the government of the United Kingdom which understands Islamic extremism as any form of Islam that opposes "democracy, the rule of law, individual liberty and mutual respect and tolerance of different faiths and beliefs".
It is not to be confused with Islamic fundamentalism or Islamism, the former defined as a movement of Muslims who are of the view that Muslim-majority countries should return to the fundamentals of an Islamic state (though some see Islamic fundamentalism as a form of Islamic extremism) and the latter being a type of political Islam. Islamic terrorism or jihadism is very often the result of Islamic extremism, although not in every case.
Definitions.
Academic definition.
The academic definition of radical Islam consists of two parts:
United Kingdom High Courts definition.
The UK High Courts have ruled in two cases on Islamic extremism, and provided definition.
Aside from those, two major definitions have been offered for Islamic extremism, sometimes using overlapping but also distinct aspects of extreme interpretations and pursuits of Islamic ideology:
UK High Court rulings.
There are two UK High Court cases that explicitly address the issue of Islamic extremism.
May 2016 appeal case.
The judge refers to several grounds: section 20 of the 2006 Act; the definition of "terrorism" in section 1 of the Terrorism Act 2000 and the decision of the Supreme Court in "R v Gul".
October 2016 Shakeel Begg case.
Begg, a prominent Muslim public figure and Imam at Lewisham Islamic Centre since 1998 lost his 2016 court case of Libel against the BBC. This case is noteworthy because the judge lists a 10-point definition of Islamic extremism that he used to determine the case:
In Charles Haddon-Cave's findings he wrote:
Extremist Islamic positions 
118. In my view, the following constitute "extremist" Islamic positions (or indicia thereof). 
Key influences of radical Islam.
Early Islam.
According to the academic definition of radical Islam, the second condition for something to be called radical Islam, is that it is antigovernmental. Consequently, a government is a condition for radical Islam. However, even though the peace of Westphalia was established in 1648 and thus introduced the nation state, the writings of the early Islam period are influential to the contemporary writings that were coined radical after the concept of the nation state was established in Islamic regions as well. Key influences of radical Islam that stem from early Islam include:
Kharijites.
According to some contemporary Muslim commentators, extremism within Islam goes back to the 7th century to the Kharijites. 
From their essentially political position, they developed extreme doctrines that set them apart from both mainstream Sunni and Shiʿa Muslims. Tradition traces the origin of the Kharijities to a battle between 'Ali and Mu'awiya at Siffin in 657. When 'Ali was faced with a military stalemate and agreed to submit the dispute to arbitration, some of his party withdrew their support from him. "Judgement belongs to God alone" (لاَ حُكْكْ إلَا لِلّهِ) became the slogan of these secessionists. They also called themselves al-shurat, "vendors", to reflect their willingness to sell their lives in martyrdom.
These original Kharijites opposed both 'Ali and Mu'awiya, and appointed their own leaders. They were decisively defeated by 'Ali, who was in turn assassinated by a Kharijite. Kharijites engaged in guerilla warfare against the Umayyads, but only became a movement to be reckoned with during the second civil war when they at one point controlled more territory than any of their rivals. Kharijites were, in fact, one of the major threats to Ibn al-Zubayr's bid for the caliphate; during this time they controlled Yamama and most of southern Arabia and captured the oasis town of al-Ta'if.
The most extreme faction of Kharijites was that of the Azariqa, who condemned all other Muslims as apostates, also known as the process of takfir. The Kharijites were particularly noted for adopting a radical approach to takfir, whereby they declared other Muslims to be unbelievers and therefore deemed them worthy of death.The Azariqa controlled parts of western Iran under the Umayyads until they were finally put down in 699. The more moderate Ibadi Kharijites were longer-lived, continuing to wield political power in North and East Africa and in eastern Arabia during the 'Abbasid period.
Because of their readiness to declare any opponent an apostate, the extreme Kharijites tended to fragment into small groups. One of the few points that the various Kharijite splinter groups held in common was their view of the caliphate, which differed from other Muslim theories on two points. 
By the time that Ibn al-Muqaffa' wrote his political treatise early in the 'Abassid period, the Kharijites were no longer a significant political threat, at least in the Islamic heartlands. The memory of the menace they had posed to Muslim unity and of the moral challenge generated by their pious idealism still weighed heavily on Muslim political and religious thought, however. Even if the Kharijites could no longer threaten, their ghosts still had to be answered. The Ibadis are the only Kharijite group to surivive into modern times.
Contemporary Islam.
The contemporary period begins after 1924. With the extinction of the Ottoman Empire, the caliphate was also abolished. This heavily influenced Islamic thinking in general, but also what would later be coined radial Islamic thought. Key thinkers that wrote about Islam in the 20th century, and especially about jihad, include:
Sayyid Qutb.
Sayyid Qutb could be said to have founded the actual movement of radical Islam. Unlike the other writers that have been mentioned above, Qutb is not an apologist. Some of the proponents of Islam emphasise peaceful political processes, whereas Sayyid Qutb in particular called for violence, and those followers are generally considered Islamic extremists and their stated goal is Islamic revolution with the intent to force implementation of Sharia law and/or an Islamic State Caliphate.
There are over 120 Islamic extremist groups active today. Below is a list of major groups active.