Six hundred men and women of the Australian Defence Force are already in the United Arab Emirates, together with a squadron of FA-18 Hornets poised to strike. After all ISIL, as the federal Attorney-General told the ABC last week, "represents or seeks to be an existential threat to us". An existential threat! When I left the United Kingdom in 1982, hundreds of missiles armed with nuclear warheads, some a thousand times more powerful than the Hiroshima bomb, were trained by the Soviet Union on those small islands. As NevilShute's On The Beach not unrealistically portrayed it, a full-scale nuclear exchange would have threatened human existence even in far-off Australia. That was an existential threat. ISIL is brutal, and merciless. It undoubtedly threatens the lives and well-being of some hundreds of thousands – perhaps millions – of people in northern Iraq and eastern Syria. It has made clear that it wants its followers to kill Australians too. But, whatever it "seeks to be", it is not and never will be an existential threat to Australia. Yet so far as I know, only Crikey's Bernard Keane has called George Brandis out on his alarmism. ISIL knows the power of terror, however. As the Prime Minister puts it, "It is a serious situation when all you need to do to carry out a terrorist attack is to have a knife, an iPhone and a victim".

But what last week showed us was that, with a bit of help from your enemies, you can terrify a supposedly confident and prosperous nation of twenty-three million people by making one call on an old-fashioned telephone. It was one call, after all, that precipitated last week's raids. Eight hundred policemen, witnessed by dozens of journalists and filmed by their own media unit's cameras, raided two dozen addresses. After what we were breathlessly told was "the biggest counter-terrorism operation in Australian history", one young man was charged with a terrorism offence. As the government made sure we knew in double quick time, he had been urged by an ISIL activist in Syria to cut off the head of an innocent Australian. One Australian. There's an existential threat for you. "Terrorists want to scare us out of being ourselves and our best response is to insouciantly be fully Australian," said Tony Abbott. And so, insouciantly, our Parliament will today debate whether to impose still more drastic anti-terror laws, in addition to those enacted by the Howard government – laws that have already limited the rights of the citizen that have been in place since Magna Carta.

In December 2012, the government made public a declassified version of a report by the National Security Legislation Monitor, Bret Walker SC. Walker advised the abolition of Preventative Detention Orders. PDOs allow the security agencies secretly to detain people for days without charge. "There is no demonstrated necessity for these extraordinary powers," Walker wrote, "particularly in light of the ability to arrest, charge and prosecute people suspected of involvement in terrorism." They had never been used. Until last week, that is. Apparently at least three people were detained under PDOs last Thursday and then released. We aren't permitted to know whether some are still being held under such orders, or why. Such powers are rarely granted to security agencies by democracies, even in wartime. The only parallels Bret Walker cites are the detention of ethnic Japanese by the United States during World War 2, and the detention of IRA suspects during the Northern Ireland "troubles". Those, said Walker, "are now recognized by both governments as policy failures". And Tony Abbott tells us that "the last thing any of us would want to do is to damage our freedoms in order to preserve our freedoms." Yet Bret Walker's advice will be ignored. Among numerous other draconian measures, the government proposes to renew legislation authorising Preventative Detention Orders for another ten years. Well, Bret Walker was a Gillard government appointee, no doubt insufficiently alarmed by the terrorist threat. "The community expects government…to keep them safe, this government will not let them down", says Tony Abbott.

Funding for ASIO and ASIS up; the Department of Climate change abolished, and funding for the CSIRO's scientists cut. More and more laws to stop terrorists; fewer and fewer measures to limit greenhouse gas emissions. And of course, no carbon price. The threat of terrorism by followers of ISIL, and the threat posed by climate change, are both real. But only one of them is potentially existential. If we expect government to keep not just us, but our children and grandchildren safe, this one let us down. Count on it. Jonathan Holmes is a Fairfax columnist and a former presenter of the ABC's Media Watch program.