Earlier this week, Sheikh Ahmed al-Tayyeb, the Grand Imam of Al Azhar, Sunni Islam's most renowned educational institute, called for educational reform for Muslims to prevent the spread of religiously inspired extremism.

Sheikh Tayyeb was careful not to associate terrorism and violence specifically with Islam. "Bad interpretations" and "a historical accumulation of excessive trends", had led Muslims to become more vulnerable to recruitment by radicals.

In contrast, the fighters of the Islamic State in Iraq and Syria (ISIS), otherwise known as "Da'ash", made sure that all who view their propaganda material of grisly executions are left in no doubt that they are doing it in the name of religion, citing chapter and verse from within the Islamic tradition.

This has led to a flurry of recent commentaries arguing that those who insist, like President Barack Obama did last week, that ISIS is un-Islamic are living in denial.

Are the Grand Imam and the President of the United States wrong then?

Is ISIS Islamic, given its explicit use of Quranic verses to justify its actions?

A key to this heated debate is to be found in Sheikh Tayyeb's scholarly term, "interpretations", of which Islam has a long and rich tradition dating back centuries.

There is a certain irony that he made his remarks in Mecca, the holiest city for Muslims worldwide and part of modern-day Saudi Arabia. The modern Saudi state arose on the back of religious support from the purist Salafi movement, which many describe more derogatively as "Wahhabism".

Sheikh Tayyeb did not go into the differences in his speech but the Grand Imam comes from within the Azhari tradition, a school of thought representative of the Sunni mainstream, and one which disagrees with Salafism in more than one area of religious teachings.

There is a further irony in that in the territories ISIS militants have taken over, they often use Saudi religious textbooks even as the religious establishment of Saudi Arabia rails against the extremists.

Of course,

One could ask on what basis does Sheikh Tayyeb judge interpretations, deeming some good and others bad?

Both comparisons are not very useful. Academia's peer review process comes closer.

Traditionally, the religious authority of Muslim theologians and jurists is first based on a rigorous education in Islam's primary and secondary texts - the Quran and prophetic narrations, but also various legal methodologies, commentaries and other such works by specialists that have been written over the centuries.

But that is not enough. The learning has also to be derived from the sanad, a long chain of transmission from scholar to scholar going back several generations.

This methodical, peer-reviewed approach to studying the texts was until relatively recently understood to be necessary to those who wish to speak with any credibility on religious matters.

Without that foundation and the discernment that is supposed to come with it, it does nothing for one's standing even if one makes a big deal of spouting verses, like what ISIS is doing now.

But purist Salafism challenged that system. Its basic claim is that the Muslim community had gone astray, deviating from the true path set by the first three generations of Muslims, the "Salaf al-Salih" or the "pious predecessors".

That meant, of course, there has to be "reform" which, given their strict literalist worldview, would mean doing away with much of the sophistication that had developed over centuries of Islamic studies.

If a political alliance had not been struck between the Al-Saud family and Salafi preachers, and oil had not been discovered in the kingdom, purist Salafism might have simply passed from the Muslim world as many other less mainstream approaches to religion had.

Certainly, there was more than one heterodox movement in the past that is now a footnote in history. But purist Salafism remained, thrived (supported by an alliance between the Al-Saud family and Salafi preachers, and oil discovered in the kingdom), and trained preachers that went around the world.

ISIS is not automatically the result of purist Salafism; it would be unfair to make such a straightforward connection. Nevertheless, without the presence of purist Salafism, it is difficult to see how ISIS could have emerged.

Its lack of reliance on traditional systems of religious authority, as historically exemplified in institutions like the Qarawiyyin in Morocco, the Kairouan in Tunisia, the Azhar in Cairo, or the old madrasahs of Tarim in Yemen, allows it to reinterpret Islam in a variety of fields which has so shocked the world.

Of course, even without ISIS, Sunni Islam would have faced a tremendous challenge in maintaining its traditional systems of religious authority.

Modernity brings literacy and while Sunni religious authorities in the past could have insisted that laymen simply trust them in matters of religion, that is no longer feasible when anyone who can read Arabic can easily access texts that were hitherto beyond their reach.

The religious establishment needs to be far more open in its deconstruction of radical* ideas - something it is more than capable of doing, but which it hitherto does far less than it ought to, out of a sense that it should be enough to simply say "this is un-Islamic".

Beyond that, and this is probably the most difficult challenge of all - mainstream religious authorities need to be able to gain "street cred".

With that kind of credibility, those sections of Muslim populations that are most vulnerable to ISIS recruitment will pay closer to attention to mainstream authorities - but they can get that kind of credibility only if they criticise the abuses of authority that is endemic in so much of the Muslim world's governments today.

Sheikh Tayyeb's efforts to improve educational standards within religious establishments, so that they are more aware of traditional notions of interpretation, and how these differ from the likes of ISIS, may be a step in the right direction, but
• Sunni Islam will need to do a lot more than (improving educational standards within religious establishments, so that they are more aware of traditional notions of interpretation, and how these differ from the likes of ISIS), it has to [energetically] deconstruct those radical*, [false and anti-traditional] ideas.

H.A. Hellyer is an associate fellow at the Royal United Services Institute in London and the Brookings Institution in Washington, DC.