In the 20th century the state was the chief enemy of freedom. Today, it is the weakness of the state that most threatens freedom. In many parts of the world, states have collapsed. In others, the state is corroded or corrupt. The result is that billions of people lack the most rudimentary conditions of a decent life. Even in many rich countries fear of crime is pervasive. Yet liberals - mesmerised by the terrible record of state-sponsored crimes against humanity - continue to believe that the main challenge of politics is to limit state power. Believing there are human freedoms that must never be violated, they insist that everything governments do be consistent with human rights.
The trouble with this simple-minded liberal philosophy is that it treats freedom as a natural condition that develops spontaneously as soon as government repression is removed. In fact, freedom is an extremely complicated and delicate construction that can be maintained only by making continuous adjustments. Contrary to the rather legalistic strain of liberalism that is currently dominant, liberty is not a system of interlocking rights that must be maintained come what may. One freedom can undermine another. Politics is the art of choosing between rival freedoms.
In the make-believe world of liberal philosophers, we do not have to choose which of our liberties we value the most. In a well-ordered constitution, we can have them all. Such is the constantly reiterated view of American liberal legalists such as John Rawls and Ronald Dworkin. In the real world, things are done rather differently. When legal niceties were tossed aside in the United States and suspects rounded up and secretly interned after last September's terrorist attacks, many liberals were aghast. Yet the American response was entirely predictable. That is what always happens when there is a serious threat to peace. No doubt the Bush administration's actions were in some respects ill-considered and excessive. Even so, it cannot be criticised simply for departing from a strict regard for personal freedom.
At bottom, the state exists to secure peace. Whenever peace is at odds with liberty, it is always liberty that loses out. As Hobbes knew, what human beings want most from the state is not freedom but protection. This may be regrettable, but building a political philosophy on the denial of human nature is foolish. It is better to face facts. Personal liberties do not naturally dovetail. Often they make competing demands, and when they do, the task of government is to craft a mix that affords citizens an acceptable degree of security.
At present, although the actions of governments often belie their words, political discourse is still fixated on fear of the state. Its thinking still addled by cranky libertarian ideas, the right harps on about the virtues of small government. The centre left recognises that size is not the issue, but insists that government must be bound by individual rights in everything it does.
What both the right and left have not understood is that if it is to provide the security its citizens demand, government should be highly invasive in some contexts and withdraw almost entirely from others. Curbs on liberty that are right in some contexts may be wrong in others. In order to protect its citizens, the state may have to subject them to high levels of surveillance. At the same time, it should stop trying to regulate people's lives where doing so is counter-productive and damaging to society.
Current attitudes to drugs and terrorism illustrate the flaws in the prevailing thinking about the state. Governments tell us that the war on drugs and the war on terrorism go hand in hand, and accordingly demand draconian powers to prosecute them. Liberals are suspicious of the rhetoric of war, and insist that governments must in both cases be bound by a regime of rights. Neither side recognises that whereas dealing with terrorism may demand an enhancement of the state's powers, coping with drug use requires a far less invasive state.
The case for legalising drugs is usually stated in terms that hark back to the 1960s: individuals should be left alone when what they are doing affects no one but themselves. This formula echoes John Stuart Mill's celebrated dictum that in the part of his conduct that concerns only himself, the individual is sovereign. Mill's principle would not justify legalisation today. Particularly when it leads to health problems, drug use cannot avoid affecting other people. Moreover, the range of drugs consumed is vastly larger now than it was in Mill's day. Drugs - legal and illegal - are products of worldwide industries whose activities have far-reaching effects on society and the economy. In these circumstances, it is silly to think that drug use falls into the category of a purely self-regarding activity.
The case for legalising drugs has very little directly to do with personal freedom. Certainly, it does not depend on the idea that drugs affect only their users. On the contrary, it is precisely because they affect society at large that their use should be legalised. Government should confine itself to education, regulating quality and providing treatment for people whose drug use has become problematic. Prohibiting drugs has led to far more casualties than drug use itself.
The first casualty of a regime of prohibition is public health. When drugs are illegal, their quality cannot be controlled. When they are used intravenously, they spread dangerous or deadly diseases such as hepatitis and HIV. A second casualty is crime control. Wherever drugs are prohibited, their price rises steeply, leading to high levels of crime on the part of users. Conversely, the profits of the illegal drugs trade are huge. As a result, criminal organisations are able to bribe the police and, in some countries, to co-opt governments. That leads on to a third casualty - global security. All over the world, terrorist organisations get a sizeable portion of their funds from the illegal drugs trade. Arguably, terrorists are the single greatest beneficiaries from the current prohibitionist regime.
Though liberals are reluctant to admit it, what is loosely called terrorism is actually a new kind of unconventional war - one that has arisen from the weakness of state power in many parts of the world. We are used to thinking of war as a form of conflict among states. That may have been largely true during much of the modern period, but it is worth noting that, over the past decade or so, warfare has begun to slip out of the control of states. The Falklands war and the Gulf war were armed encounters between states, but in the Balkans, Afghanistan and, more recently, the Middle East, war has followed a different pattern.
In each case, some of the protagonists are not states, but political organisations or fundamentalist networks over which no state has much leverage. The al-Qaeda group seems to be one such network. Governments like to talk about defeating or eradicating terrorism, but in fact the task of controlling such groups is open-ended and dauntingly difficult.
One reason why the Bush administration's obsession with securing a change of regime in Iraq is so badly misguided is that it will do little to hamper the activities of terrorists, and - by further alienating the Arab world - may end up making the job of containing them harder. There is a deeper flaw in this thinking. Where there has been nothing resembling a modern state for some time, as in Afghanistan, the use of force can achieve only very limited ends. This is even more clearly true in Iraq, where the state could well break up in the aftermath of a US attack. Whether or not it can be morally justified, waging war in these circumstances is futile unless it is followed by a long period of state-building.
At least in America, official thinking does not accept the need to renovate the state in countries where it is weak. Unfortunately, liberal thinkers contribute to this intellectual default by identifying states as the principal violators of human rights. That may have been true during much of the 20th century. Only a modern state could have perpetrated the Holocaust or established the Gulag. The world still contains many highly repressive states. Nevertheless, the risks most potentially catastrophic to human rights no longer emanate from states. The last big genocide of the century - in Rwanda - was the work not of a state, but of irregular ethnic militias. Equally, the current threat from weapons of mass destruction is not that states will use them, but that they may leak out of the control of states. Today, weak states pose a greater danger to human freedom than tyrants.
Liberals refuse to accept this. They are adamant that the dangers arising from terrorism cannot justify new restrictions on liberty. Rightly, they point to the fact that once governments acquire such powers, they rarely give them up. Certainly David Blunkett's proposals for monitoring communications were absurdly sweeping. But are we really unwilling to give up any of our freedoms, if that is the price of reducing the risks of catastrophe?
From Locke to Mill, Kant to Rawls, liberal thinkers have tried to put the state in a straitjacket. In our time, Hobbes may be a better guide than any of these worthies. Freedom is not the normal human condition. It is an artefact of state power. If you want to be free, you need first to be safe. For that, you need a strong state. Hobbes understood this because he lived in a period of civil war. Let's hope we do not have to suffer something similar - or worse - before we stop demonising the state.
John Gray is professor of European thought at the London School of Economics. His next book, Straw Dogs: thoughts on humans and other animals, is published by Granta in September