If you live in an authoritarian state the answer to the question 'How do you fight terrorism?' is relatively straightforward. I say 'relatively' because it is by no means a simple question even for dictators. In recent decades even authoritarian governments have had to weigh up the most effective method of fighting terrorism and it hasn't always just involved applying as much repressive force as possible.

But for a democracy, or more specifically a liberal democracy, fighting terrorism is not straightforward because it is not just a matter of efficacy; it is also a matter of rights and values. In defending itself against terrorism, a liberal democracy is not just protecting the physical security of its citizens, it is also defending the integrity of the political system in which these citizens participate.

So while an authoritarian government must simply find the most efficacious way to fight terrorism, a liberal democracy must find methods that are effective but which do not undermine the rights and values that distinguish the political system, most notably the rule of law and the various freedoms (of expression, of assembly, of the press etc) that make up our civil liberties.

I think we have entered a period, which may well last as a long as a decade, in which Australia will face a far more serious terrorist threat than it faced in the aftermath of 9/11. It is a threat we will face as much at home as we will abroad, as the events at the Lindt Café last December underline. 

But in responding to that threat it is not enough to simply ask what further powers or resources we can provide to our intelligence agencies and police forces. We also have to ask ourselves what damage these and other steps do to the values and rights that define us as a society. We have to ask ourselves: how do we find the balance between security and liberty?

Of course, this is an old debate, predating even the terrorist threats we have faced in recent years. All democracies to some degree compromise the liberties of their citizens to protect them from a variety of domestic and external threat and to preserve the political system in which they live. Freedom does have some necessary limits.

Yet as old as this debate about liberty versus security is, we are not really having it in Australia at the moment. There are echoes and fragments of it, most often when things go wrong (either a gross transgression of liberty or a terrorist attack). But mostly the two sides of this debate talk past each other rather than at each other.

On the one hand, the proponents of liberty will focus on the rights and the freedoms they argue are being undermined in the fight against terrorism. Too often, however, this group will tend to minimize or downplay the threat. Terrorism, they say, is hyped; more people, they argue, will die falling off ladders than will die at the hands of terrorists.

On the other hand, the proponents of security will argue for significant new resources and powers for the agencies fighting terrorism and new limits placed on those parts of the community from which the threat is seen to come. But too few in this camp ask whether, in taking these measures, we are doing more damage to our society and principles than the terrorists are.

I would like to see a debate in which the proponents of liberty acknowledge the threat, understand that it provokes genuine fear in much of our society (even if more people die falling off ladders or in car accidents) and then ask themselves which of our liberties we should compromise for the sake of security. As the Charlie Hebdo case underlined, we don't even seem to be clear about the liberties we are defending.

I would like to see a debate where the proponents of security recognise that the threat to our societies comes not just from terrorism but from the way in which we fight terrorism, and that we should be prepared to accept certain levels of risks for the sake of preserving our rights and principles.

I am probably being naïve in expecting such a debate to take place. It is not just on this issue that we talk past each other. Nevertheless, I am convinced that we need to have that debate, not least because I fear that we will see more episodes like that which played at the Lindt Café in the years to come.