A nightmare, indeed, but unlike most nightmares, this one has a worthwhile message. For we can learn something from this both about ourselves and the societies we have created.
If our worries fall into two groups - the threat from technology and the threat from maverick social groups - the greater concern for most people is probably technology. The legacy of this century has been to create a stock of equipment which was either specifically designed for the purpose of killing people (nuclear bombs, nerve gas) or which offers a convenient method of so doing (Semtex explosive). For most of the second half of the century the world has managed to keep most of this equipment in reasonably responsible hands. Nevertheless it has been possible for Saddam Hussein to use nerve gas on his own people and for the IRA to have obtained a sufficiently large stock of explosives to carry on its bombing campaign for at least another 10 years.
It would be naive not to acknowledge that the spread of weapons of war will continue: the sheer volume of military kit in the former Soviet Union for which there is no longer any direct use will see to that. Terrorist groups will be able to continue to find ways of obtaining the tools of their trade. But there is a powerful argument to be made that the spread of killer technology is not the most serious problem.
For a start, you don't actually need great technological sophistication to do an enormous amount of damage: the IRA's Bishopsgate bomb was based on agricultural fertiliser; tens of thousands of people are killed in the US every year with handguns. And the really catastrophic technologies, such as nuclear weapons, are complex, difficult to deploy and, for the moment at least, quite tightly controlled. Most important of all, technology cuts both ways. The counter-terrorist weapons of a modern state are developing just as quickly as the terrorist armoury. Deploying those counter-terrorist weapons imposes inconvenience and cost - security searches at airports were unknown in the Fifties - but provided people are prepared to accept these prices, any known threat can be contained. Fewer planes are hijacked now than in the Seventies.
The array of a state's anti-terrorist weapons is of less help when the threat is new, unknown or unknowable. Anyone who has used the Tokyo subway will be aware that it is a model of reliability, order and precision. The people who use it are visibly more ordered than the passengers on, say, the London, Paris or New York systems. (Even the intense crowding is ordered: people push each other at exactly the right time to get them in and out of trains in the most efficient way.) It would be the last urban transport system you could conceive of being disrupted by terrorists. But if the attacks were to be repeated, Japan would develop technology to cope with them.
In building giant cities, of course, we have made it much easier for terrorist groups. One hundred years ago there were no urban agglomerations with more than 10 million inhabitants. By the end of this century there will be perhaps 30 - the tally depends a bit on how widely the boundaries are drawn. When something like the Tokyo attack or the City of London bombing occurs, it reminds us how the complexity of these cities - the airports, the telecommunications networks, the water supply and the mass transit systems - makes us all vulnerable to terrorism.
However, much more alarming than the spread of killer technology is, I suspect, the other aspect of the Tokyo incident: that a small group could feel strongly enough about something to mount a random and lethal attack. My worry is less that the structure of our cities makes then unusually vulnerable, than that the forces creating them are themselves destabilising: the very growth of urban society is likely to generate terrorism.
Giant conurbations are the result of very rapid population growth and associated large population movements. The new giant cities are not in the relatively settled rich world, but in less developed countries. Any sudden population increase means there are many more young people, people with energy but in many cases without jobs. Any large movement of people means the roots of the society - villages, families - no longer have much influence over the population. The creation of new giant cities (often without the service infrastructure of the old ones adjacent to them), and the formation of a new rootless urban poor are part of the same process. This process is bound to lead to greater disparities in wealth and opportunity. Some people do very well out of urbanisation, but the majority do not, and yet the two groups are physically compressed together.
Most people in the world are too sensible, balanced and humane to vent their frustration or alienation in the form of terrorism: urban crime maybe, but not indiscriminate attacks on the general population. But any country which is unable to satisfy the reasonable aspirations of its young people is creating potential for terrorism. And this will build not just in the less developed world; in many North American cities (and even in parts of European ones) large numbers are either excluded from the mainstream of prosperity, or choose to exclude themselves from it.
So the Tokyo attack is liable to lead us to the wrong conclusion: that the prime problem is committed terrorist groups, with access to high-technology weaponry, directing these weapons against the populations of the complex cities of the rich world. It is not: the tensions of the world are no longer primarily between countries or power blocs, but between different groups of people within countries. It would be astounding if, from time to time, these tensions did not burst out in the form of terrorist attacks.
Are there lessons for Britain in all this? Perhaps the most important point is that we become more sensitive to the concerns of groups who are, in whatever way, excluded from the mainstream of society - and find ways of mediating their conflicting needs and demands. In a place like Britain this means accepting a diversity of opinion and lifestyles. But it also means requiring the small groups of people who feel very strongly about something not to push those views beyond certain specified limits. We need to be clearer about rights, but also about duties. Yet perhaps we can take some comfort, too: untidy, heterogeneous cities are in some ways healthier places for people to get along than over-orderly, wealthy, homogeneous Tokyo. We are all going to have to learn to live cheek by jowl with dissent.Reuse content