We ought to wonder how a Government that weeks ago seemed incapable of attracting and holding our trust is now cast as the solid paternal guardian against nameless dread, writes Jonathan Green.

Is there anything more disconcerting than unflinching certainty?

It's not supposed to have that effect, especially not in politics, where doubt is commonly taken for weakness and where confidence signals strength.

Right now, that confidence just doesn't ring true.

Common sense tells us that confronting the influence of the Islamic State on its ardent local followers, on impressionable hotheads, on the lost and disaffected, is not going to be a simple matter.

Common sense would also suggest that many of the possible responses could have the opposite to intended effect, that despite the instinct to flinch back from Muslim Australia with fists clenched, a closer embrace might do more to boost everyone's sense of security and trust.

A young man was killed on Tuesday after a savage assault on police, an act that by this morning has come to be a living Rorschach blot, a shadow to be shaped by our various certainties.

Was Abdul Numan Haider the "quiet, very gentle, very softly spoken" young man who "seemed to be looking for answers, and asking questions ... trying to work out his place in the world, and in Australia, as a young Muslim man".

Or was this "a tale of an impressionable young Australian Muslim who became so entranced by the murderous ideology of Islamic State that he saw himself as an Islamic State soldier in a foreign land."

Quite possibly he was both.

For some commentators, it was a killing as inevitable as the soft-headed denialism that attempts to soften its fundamental horror with reason: "We took in boat people from Afghanistan to give them refuge. Now it's Australians who need refuge ... Once again the dangerous and frankly offensive denialism and blame-shifting ... The police are the problem? The failure is ours? The 'root cause' is alienation, not Islam and some of its reckless representatives?"

"This blame-shifting happens too regularly from Muslim leaders that it now seems not a misjudgement but a tenet of their ideology."

What we all might agree on is that it was an act of contradictions and some mystery, either the crazed violence of an isolated individual or the single face that gives shape to the previously invisible zombie horde; the seething unknown mass of the suburban "death cult".

According to the Attorney General, George Brandis, it's a group that "represents or seeks to be an existential threat to us", never mind that it may only constitute confused and angry individuals, not some coherent warrior mass.

Which is of course the problem with the "lone wolf" phase of this war on terror: that we are confronted by the menace of individuals, unknowable and elusive. That's the problem, but also the inherent contradiction: they are still only individuals.

Their acts of violence, if and when they come, will be criminal acts. No more or less.

We make a constant calculation with criminality, a balance between prevention and civil liberty that errs toward liberty.

This is the civilised balance we keep, a calculation that sets worrisome probabilities against essential and defining freedoms.

The result is a trade-off in our relationship with criminality: we enjoy a society so free that even crime may exist.

We could attempt to cauterise it, to clamp down on human liberty so sternly that wrong doing would have no wriggle room, but we calculate risk against return.

Or we used to. These sands are shifting. As the Prime Minister told the Parliament on Monday:

Regrettably, for some time to come, Australians will have to endure more security than we're used to, and more inconvenience than we'd like. Regrettably, for some time to come, the delicate balance between freedom and security may have to shift. There may be more restrictions on some so that there can be more protections for others.

In our Senate this morning debate resumes on legislation that seeks to reset those scales in the firm concrete of law, law that may see journalists imprisoned for reporting state secrets in the public interest, may see your devices tracked, your data horded. The debate will be coloured by events, will be driven by the tensions of a moment and the frustrations of a state security apparatus that confronts that most elusive of threats: the acts of maddened individuals.

As Senator Brandis told his colleagues yesterday: "Freedom is not a given. Freedom must be secured particularly at a time when those who seek to destroy those freedoms are active, are blatant and are among us."

As the joke goes: if they hate us for our freedoms, perhaps removing that freedom will make us safer.

Our politicians will continue to speak with tremendous certainty and assurance, but the rest of us ought to wonder.

We ought to wonder how a Government that weeks ago seemed incapable of attracting and holding our trust is now cast as the solid paternal guardian against nameless dread, how our fears have ennobled it.

We ought to wonder how an Opposition can be so desperate to share those spoils of our anxiety that while it talks down every Coalition gesture in economics, education, health and all the rest, it can find only unbounded praise for everything the Government does in national security. Somehow it manages to get that so defiantly right.

We ought to wonder, with whatever calm we can muster, just how much we are prepared to give to secure ourselves against the unknown.

And perhaps we ought not be so certain.

Jonathan Green hosts Sunday Extra on Radio National and is the former editor of The Drum. View his full profile here.