The close timing of the stabbings at Bondi that saw six people murdered on Saturday, and the fortunately non-fatal stabbing attack at Wakeley on Monday night, inevitably focused attention on what constitutes terrorism. The latter attack has been deemed terrorism; the former hasn’t, at least at this stage.

Much hinges on declaring an event terrorism. In NSW, it means police are given draconian powers to infringe basic civil liberties, such as warrantless searches. The definition of an act of terror is also extraordinarily vague and includes actions that are already criminal offences, such as causing serious physical harm, causing serious damage to property, causing death or endangering a life, creating a serious risk to public safety, or sabotaging electronic and financial infrastructure. What elevates them to terrorism is the intention to “advance a political, ideological or religious cause”, with the added element of coercing or intimidating governments or the public.

The vagueness of “ideological” allows the definition to evolve. It’s now a given that misogynistic violence can be terrorism. ASIO head Mike Burgess, reflecting on the need to avoid being tied to traditional notions of terrorism, has specifically identified “incels” as a potential terrorist threat, albeit one that so far has imposed on his agency little in the way of caseload.

It wasn’t always thus. After then attorney-general George Brandis spoke on terrorism in 2014, I asked him why there was such a focus on terrorism compared to domestic violence, which killed far more people. His response was to go red and angrily attack my linking of the two.

Given the Bondi perpetrator targeted women, his murders may yet be seen as having been committed as part of an ideological cause. So far, however, his long and well-documented mental health problems are considered the main driver of his actions.

But there is evidence that people with mental illness are overrepresented in the ranks of terrorists, particularly so-called “lone wolf” attackers. Some researchers dispute the link in the Australian context, but evidence from overseas from jihadists, white supremacists and Northern Ireland paramilitary groups is strong.

The link comes with extensive caveats: the broader non-terrorist criminal population has higher rates of mental illness as well; correlation is not causation; trauma can cause mental illness as well as radicalise people; there is evidence terror groups target people with mental health problems for recruitment; and case studies show that mental illness, while it may be present, is not necessarily a determining factor in violent actions.

So, short of a more comprehensive and conclusive study of how ideology, life circumstances and mental health mix in the minds of terrorists, if there’s a spectrum stretching from purely mental health-related actions and purely ideological actions, declaring something an act of terrorism is likely to represent an arbitrary selection between the two.

Declaring a violent act terrorism, however, seems to be accorded far more importance by society than merely being a trigger for draconian police powers. It dictates how we are allowed to feel about an event. A certain breathlessness awaits the announcement by police that certain violence was or was not terrorism (except for those keen to inflame division, who don’t bother waiting). Deeming an event terrorism slots it into a well-known category, about which we know how to think; we can understand the motivation of the attacker, and respond according to how we feel about traditional sources of terrorism such as radical Islamists or right-wing extremists.

However horrific, terrorism is also amenable to governmental intervention and public policy. Terrorists can be shot and bombed, surveilled and negotiated with. Their actions, and the success or failure of their attacks, will partly hinge on the effectiveness of security agencies. There’s an entire defence and security industry, and bureaucracy, that draws life from terrorism. The media, too, sees it as a lucrative opportunity, to frighten audiences and engage in the kind of trauma porn that we’ve been inundated with in recent days. That is, terrorism is normalised as a familiar, straightforward and exploitable concept.

But to leave a mass killing in the realm of mental health is far more unsettling. Yes, such events become cues for demands for changes to public policy, in more mental health and homelessness services. Such demands are entirely justified even without these horrific events. But the seemingly arbitrary nature of such explosions of violence from lone men, and the pointless deaths and trauma they cause, can never be adequately guarded against — and certainly not in a society that values civil liberties.

To accept “mental health” as an explanation for fatal violence is to accept that some horrible events, random and wholly unjust in their very nature, can’t be stopped. It’s to catch a glimpse of a world entirely indifferent to us and to justice, in which good people suffer senseless deaths through sheer chance.

In that way, declaring something “terrorism” is a security blanket, a comfort that we, or at least governments, however inept, are somehow in control and not the victim of something much darker lurking in the flawed minds of broken men.

How do you think the definition of terrorism affects out perception of an event? Let us know your thoughts by writing to letters@crikey.com.au. Please include your full name to be considered for publication. We reserve the right to edit for length and clarity.