The lone wolf is the new national nightmare, dramatized and amplified this week by the hostage-taking attack in Sydney, Australia. But there are two kinds of lone wolves – the crazy and the evil – and the distinction is important.

The real terrorists are rational. Maj. Nidal Hasan, the Fort Hood shooter, had been functioning as an Army doctor for years. Psychotics cannot carry that off. Hasan even had a business card listing his occupation as S of A (Soldier of Allah). He then went out and, shouting “Allahu Akbar,” shot dead 13 fellow soldiers. To this day, Hasan speaks coherently and proudly of the massacre. That’s terrorism.

Sydney’s Man Haron Monis, on the other hand, was a marginal, alienated Iranian immigrant with a cauldron of psychopathologies. Described by his own former lawyer as “unhinged,” Monis was increasingly paranoid. He’d been charged as accessory to the murder of his ex-wife and convicted of sending threatening letters to the families of dead Australian soldiers.

His religiosity was both fanatical and confused. A Shiite recently converted to Sunni Islam, his Internet postings showed not just the zeal of the convert but a remarkable ignorance of Islam and Islamism. He even brought the wrong Islamic banner to the attack. He had to ask the authorities to provide him with an Islamic State flag.

Which led to a frantic search to find an Islamic State connection or conspiracy. But for the disturbed like Monis, the terror group does not provide instructions, it provides a script. It offers the disoriented and deranged a context, a purpose, a chance even at heroism.

I suspect this is the case with most of the recent cluster of lone-wolf terrorist incidents, from the beheading of a fellow worker in Oklahoma to the Queens ax attack on New York City police. We fear these attackers because the psychopathological raw material is everywhere, in the interstices of every society. Normally in and out of mental hospitals, in and out of homelessness, some are now redirected to find a twisted redemption in terror.

Nonetheless, in the scheme of things, the crazies are limited in what they can carry out. They are too disorganized to do more than localized, small-scale damage. The larger danger is the Maj. Hasan with his mental faculties intact and his purpose unwavering.

The still greater threat is organized terror, as we were reminded just hours after Sydney by the Taliban attack on a school in Peshawar that killed at least 148, mostly children.

This is evil in its purest form. Consider that many of the children were killed not by explosive device or sprayed gunfire but by a single bullet to the head, the point-blank execution of an innocent, rivaling in sheer barbarism the mass murders of the Islamic State and its proud videotaped beheadings of hostages.

The purity of such evil is clarifying. It banishes thoughts of negotiation or compromise. Indeed, in response to the Peshawar atrocity, the Pakistani Prime Minister suspended his country’s prohibition of the death penalty.

In the face of similar savagery, Barack Obama committed the U.S. to a military campaign against the Islamic State. Which, if successful, would not just affect the region. Reversing the fortunes of the terror masters abroad is the key to diminishing the lone-wolf threat at home.

These groups inspire and influence because of their prestige, which, as for most messianic movements, depends on their successes – measured in growing power, territorial conquest and persuasive propaganda.

You don’t find many local terrorists invoking al-Qaeda nowadays. They fly the flag of the Islamic State. It is the strong horse, on the rise.

The first line of defense against lone wolves is, of course, protective measures: identification, tracking and pre-emption. But given the sheer number of the disturbed, unstable and potentially impressionable among us, and given the strictures that civil liberties have placed on prior restraint, that defensive posture can take us only so far.

The Islamic State has discovered that the projection of terror does not depend, al-Qaeda-style, on sending expeditionary cells to kill infidels abroad. It can do so long-distance by inspiration, by wire, as it were. Which is why the ultimate line of defense against lone wolves is to turn the fortunes of the warrior tribes themselves, the script writers of jihad.

The great new specter is the homegrown terrorist. But he is less homegrown than we imagine. He is fed from abroad. Which is where, as ever since 9/11, the battle must be fought.

© 2014, The Washington Post Writers Group