The question of religious violence hasn’t become any less resonant since last we spoke to Charles Selengut.

Dr. Selengut, who lives in Teaneck and is a member of an Orthodox congregation there, is a professor of sociology at the County College of Morris. Our talk, a few months ago, was about a new edition of his book, “Sacred Fury: Understanding Religious Violence.” This time the occasion is a talk scheduled for Sunday evening in Teaneck on a not-unrelated topic, “The Many Faces of Islam: How Modernists, Traditionalists and Militants Face the Islamic Future.”

The cloud hanging over our conversation on Sunday was the terrorist attack in the Sinai desert two days before, when 40 gunmen attacked a Sufi mosque during Friday services. With guns, bombs, and rocket-propelled grenades, they killed more than 300 people. The murderers are believed to be affiliated with the Islamic State’s Sinai branch, which earlier this year promised to eradicate Sufi practices and practitioners.

Muslims killing Muslims highlights the multifaceted nature of Islam.

“In many ways this violence is an internal struggle within Islam,” Dr. Selengut said. “The Sufis are heretics to many orthodox Sunnis, particularly to the fundamentalists. They’re a little like the chasidim of the Muslim world. They worship saints. The mainline Sunni say this is a diminution of the unity and oneness and monotheism of Allah. The Sufis’ beliefs, their dancing, their more mystical theological oneness, makes them be seen as not being true Muslims who believe in monotheism. They’re under suspicion by orthodox Sunnis.”

Not that most traditionalists would join with the militants, Dr. Selengut said. And not that this internal conflict is unique to Islam. “The parallels to Judaism are frightening,” he said. “Look at what’s going on in Jerusalem.”

Dr. Selengut was referring to the protests in Jerusalem that Sunday afternoon, protests that closed streets for hours. The protests were called by one faction of Israel’s charedi ultra-Orthodox community in response to yeshiva students being imprisoned for failing to register for the draft.

“The other group, the Bnei Brak group, called the protesters evil-doers,” Dr. Selengut said.

Two groups of ultra-Orthodox Jews, each convinced the other is doing the devil’s work and that they are the only community following the Torah and God’s will. “All religions interpret their texts in different ways,” Dr. Selengut said. “And some ways lead to violence. All religions have this penchant for violence in the extremes. Yigal Amir, who assassinated Yitzhak Rabin, was an Orthodox Jew.”

He said that Islam does have some violent tendencies that Judaism and Christianity do not share. “In Islam, the call to Muslims is that the entire world should be under the aegis of Islam. All governments, all states have to be under the auspices of Islam. This is given in the Koran. A fundamentalist could use these texts to encourage violence.

“Mohammed himself was a religious leader and a general engaged in war,” he continued. “When Islam felt itself weak and unable to conduct war, it became quiescent. This goal of Islam” — dominating the world — “was repressed or kept quiet with the idea that sometimes it would be acted on. What Al Qaeda and the Islamic state did was reignite the old texts and beliefs. They said we can’t wait anymore, we have to do it right now.

“Historically in Islam there was a fear of civil war. They always fought to keep it down. The idea of jihad had to be proclaimed by respected imams. You didn’t just wake up one morning and do a jihad. A committee, as it were, considered the law, and then they decided whether to do a jihad.

“In the 20th century, the new theologians said, ‘We can’t wait any longer for the establishment imams to proclaim a jihad. They lost their courage. Jihad has to come from bottom up. Ordinary people, laymen can proclaim a jihad.’”

This started in the 1940s and 50s, Dr. Selengut said. It was spearheaded by Egyptian theologian Sayyid Qutb, a leading member of the Muslim Brotherhood, who was arrested and executed for plotting the assassination of Egypt’s President Gamal Abdel Nasser.

“Since then people went further,” he said. “They said any individual at any time can act in a jihadist fashion. So now we have people in England or France or the U.S. getting in a car and mowing down people. This never happened in Islam before.”

When Mr. Qutb proclaimed his doctrine, “the establishment looked at it as crazy. As in all religions, the changes come from the periphery. Individual jihad is still a minority position, but it’s very potent, as we see.”

As the doctrine has evolved, ironically it has made Al Qaeda appear moderate.

“Al Qaeda under Bin Laden were violent and terrorists, but tended not to want to attack others Muslims,” Dr. Selengut said. “Not generally. Their goal was to encourage the Muslim masses to accept the more fundamentalist Wahabi reading of the texts, and then institutionalize the caliphate.

“The new group, the Islamic State, said they don’t need to wait for the masses to become more observant. We need to bring back the original Islam right now. So they kill and maim other Muslims they see as heretic as well.

“The present killing also has political ends. As the Islamic State is collapsing in Iraq, they’re retreating, and these terrorist attacks will probably increase. This is now their arena for religious violence and action, having pretty much lost their territory in Iraq and Afghanistan.”

Yet if even the most traditionalist religious interpretations are subject to change, what does that bode for Judaism?

“One of the differences is that in Judaism, if you don’t do the right thing, they won’t give you an aliyah. But they won’t kill you. Nothing in Judaism even mimics that kind of violence. It’s not the same.

“But look what’s happening at the Kotel right now. What do the Reform want to do? They want to read from the Torah with men and women. They’re not burning down the Kotel, they’re not making a fire on Shabbos. But they’re greeted with violence. It’s not violence in the sense of Islamic violence, but you see the future of the very Orthodox. It has come to that at the Kotel.”