For years, terrible and violent crimes have been committed in the name of Islam. Does that mean Islam is inherently a religion of terrible violence?

The scholar Daniel Pipes has long argued that it is a mistake to attribute the evils committed by Muslim supremacists and jihadist killers to Islam itself, or to the text of the Koran and the hadith, the religion’s sacred scriptures. Like every great faith, Islam is what its adherents make of it. Today, many of those adherents are influenced by Islamism, the militant totalitarian version of Islam that emerged in the 20th century. The Islamist ascendancy is reflected in the savageries of al-Qaeda, the brutal misogyny of the Taliban, the apocalyptic hostility of the regime in Iran.

But just as the nightmare of the Third Reich was far from the totality of German culture and character, so Islam’s 1,400-year history is not encapsulated by the violent ugliness of the present moment. In other eras, Muslim society was known for its learning, tolerance, and moderation. “If things can get worse, they can also get better,” Pipes writes in the current issue of Commentary. As recently as 1969, when he began his career in Islamic and Middle Eastern studies, Islamist extremism was all but unknown in world affairs. “If Islamism can thus grow, it can also decline.”

Since 9/11, Pipes has summarized his approach to the threat from Islamist terror and oppression with the maxim “Radical Islam is the problem; moderate Islam is the solution.” Obviously radical Muslims disagree – but even Turkey’s Islamist prime minister Recep Tayyip Erdoğan, often held out as the face of moderate political Islam, rejects the distinction, insisting that “Islam is Islam and that’s it.”

Many non-Muslims disagree, too. The prominent Dutch politician Geert Wilders, who wants the Koran to be banned in Holland, maintains that Islam and Islamism are “exactly the same” and that moderate Islam is “totally nonexistent.” Islam is not a religion like Christianity or Judaism, Wilders told me in a 2009 interview. “It’s an ideology that wants to dominate every aspect of society.”

To those who hold this essentialist view, Islam’s teachings are immutable; the values promoted by the Koran and other Islamic scriptures are today what they have always been and always will be. By this argument, the backwardness, repression, and violent incitement against non-Muslims that hold sway in much of the contemporary Muslim world don’t reflect a particularly harsh and unenlightened interpretation of Islam – they are Islam.

Not true, asserts Pipes. “Only … by ignoring more than a millennium of actual changes in the Koran’s interpretation” – on topics ranging from jihad to the role of women to slavery – “can one claim that the Koran has been understood identically over time.” Take the Koran’s famous injunction (2:256) that “there be no compulsion in religion.” Is that a call for universal religious tolerance? Does it apply only to the various denominations within Islam? Was it limited to non-Muslims in seventh-century Arabia? Is it to be understood as purely symbolic? Does it protect only non-Muslims who agree to live under Muslim rule? Was it overridden by a subsequent Koranic verse?

As Pipes and other scholars have shown, the correct elucidation of the phrase is: All of the above. There is no monolithic reading of that seemingly straightforward passage. Muslim authorities have variously given it completely incompatible interpretations.

Like all religions, Islam changes. And like all scripture, the meaning of the Koran’s text depends on its expounders. The words may be enduring, but the lessons drawn from them need not be. The Hebrew Bible and the New Testament also contain passages whose normative meanings changed as the faiths based on them evolved. Do Jesus’ words in the gospel of Matthew – “Think not that I am come to send peace on earth: I came not to send peace, but a sword” – mean that Christianity is not a religion of peace? The answer to that question is not the same today as it would have been during the Crusades or Europe’s wars of religion.

It is only fanatics who believe that they alone are in possession of the sole correct answer to every important question, and entitled to enforce it through power and persecution. The credo of the Muslim Brotherhood, which until last week’s coup was Egypt’s ruling party, declares categorically that “Allah is our objective. The Prophet is our leader. The Koran is our law. Jihad is our way.” That authoritarian, supremacist line – the Islamists’ line – is only one understanding of Islam. As millions of Egyptian citizens have made clear in recent days, it is by no means unanimous.

Radical Islam – not Islam itself – is the menace that must be defeated. In that struggle we have no more invaluable allies than moderate Muslims. Pretending they don’t exist helps no one but the Islamists.

(Jeff Jacoby is a columnist for The Boston Globe).