When someone attacks you or yours, you strike back and you strike back hard. That is not just the natural, instinctive response - it is the right and moral course of action. Failure to do so betrays a fundamental lack of self-esteem; if your own life and the lives of those you love are not worth defending, what is?
Although the targets in this month's terrorist shootings were Parisian, they were direct attacks on us, too. They were direct attacks on the Western ideal of a liberal, democratic, open society. This ideal is the exception in the world, not the norm. Most people in the world do not live under stable democracies. Most people in the world do not enjoy the social, political and economic freedoms that we take for granted.
Our way of life is rare and precious and when attacked in this way it must be defended.
Acknowledging that an attack requires a counter-attack is one thought process. Formulating an approach for that counter-attack is another. A number of different proposals have been made since the attacks two weeks ago. US Senators, and perennial hawks, John McCain and Lyndsey Graham proposed sending 20,000 ground troops to the region. David Cameron wants Parliamentary authority to conduct air strikes against ISIS. Jeremy Corbyn disagrees but offers nothing in response. Actor Mark Rylance wants to negotiate.
All of these approachees are flawed, some flawed beyond belief. Mark Rylance is simply ludicrous; what evidence does he have that ISIS would be amenable to discussion? How do you negotiate with a group whose stated aim is the destruction of your way of life, the enslavement - literally enslavement - of Western women and the crucifixion of their enemies? A group that wants to bring about a religious Apocalypse? This suggestion cannot be taken seriously.
Graham and McCain appear to have learnt nothing. Even Tony Blair now acknowledges that the 2003 invasion of Iraq contributed to the rise of ISIS. At the height of intervention there were almost 200,000 coalition troops in Iraq. Given the failure of Western military intervention, even with such a high number of troops, it is difficult to see how a reworking of the same strategy, but with fewer soldiers, could lead to victory against ISIS - a far more perfidious enemy than Saddam Hussein.
Jeremy Corbyn adds little to the debate, other than to create a situation where Britain's main opposition party has no policy on the most important national security question in a decade.
A campaign of air strikes, as proposed by David Cameron, is a Parliamentary vote away from reality. On the surface, it seems like a reasonable course of action. Air strikes are disruptive. They immediately destroy military and economic capability. They can cause our enemies to fear us. But to what end? The United States has been conducting air strikes in Syria for more than a year, yet this did not prevent two attacks on France, a key American ally, within that year.
Air strikes are comparatively an easy option for Western leaders. They can be organised rapidly. They are inexpensive compared with ground intervention. They rarely, unless bad luck or incompetence intervene, lead to friendly casualties. They give a very immediate appearance of action. A country cannot, however, air strike in a vacuum. To do so is to misunderstand both how military action works and the nature of the threats posed by ISIS.
Military action occurs at three levels: tactical - boots on the ground, aeroplanes in the air, ships in the sea - operational - armies, air combat groups and fleets acting in coordination in pursuit of specific goals - strategic - the underpinning political and philosophical ideas behind military action. The North won the American Civil War because Abraham Lincoln, facing threats not dissimilar to those facing Western leaders today, formulated a successful strategy early in the war. Jefferson Davis in the South failed to do likewise. The proposed air strikes barely register on a tactical level, never mind operationally or strategically.
Most recent Western interventions have failed at the strategic level, yet lessons have not been learnt. Perhaps - perhaps - air strikes could be successful as part of a credible, carefully calibrated and closely argued strategy, but there is none. This suggests that Western leaders either do not understand or do not know how to counter the threat posed by ISIS.
The threat is two-fold. The immediate threat to Britain, the United States and our allies is that of terrorist attacks in our major cities, perpetrated by people who may well be citizens of the nation they seek to attack. This has been the case for some time. The precise nature of the threat has evolved from suicide bombers ten years ago to marauding active shooters as seen in Paris the other week. The longer-term threat is the presence of the ISIS caliphate and the potential for a drip-feed of radicalised individuals transferring back-and-forth between Syria and the West.
It is hard to understand how air strikes will solve any of this. Although the ISIS caliphate demands territory and buildings and army bases and all the other trappings of a state, at the root of all the threats is an idea - an evil, hateful, barbarous idea - and you cannot bomb an idea out of existence. Strikes without strategy will further radicalise our enemies at home and abroad. They could be worse than useless.
Like Abraham Lincoln, our leaders need to formulate a strategy for dealing with threat the West faces. We need to strike back, but we need to do so in an intelligent and measured way. Our strategy must be intelligence-led, self-interested and confined to containing and elmininating the threat, not building nations. We must, for the sake of self-preservation, try and introduce secular democracy and free-market capitalism into the region but we must also accept that you cannot impose those ideas at the barrel of a gun.
Above all, we must not repeat the mistakes of the past. As Lincoln said in his 1862 message to Congress, 'The dogmas of the quiet past, are inadequate to the stormy present. The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew, and act anew. We must disenthrall ourselves, and then we shall save our country.'