There are several reasons why Wolfgang Sofsky is peculiarly well qualified to speak about the huge loss of privacy that we in the putatively liberal democracies of the West have already allowed to happen. One is that he is a sociologist, a student of society; another is that he lives in a country - Germany - that in living memory has experienced two forms of totalitarianism; and a third is that he cares about civil liberties in a way that most of his contemporaries have either never done, or have forgotten.

So he speaks out, with eloquence and anxiety, about the betrayal of liberties for which generations fought and died, from the dawn of the Reformation to the end of the Cold War. It is a betrayal all the worse for being unintelligent, clumsy and half-blind rather than sinister, though once the new instruments of repression are to hand in this over-technologised world of ours, the sinister will have a field day.

In this absorbing and upsetting little book, half pungent polemic and half meditation, Sofsky describes how, by means of CCTV cameras and the tracing of mobile phone calls, bus pass use, credit card purchases, e-mail, indeed in almost all ordinary interactions whether in shops or with bureaucracies, every individual is transparently and luminously traceable, leaving a glowing smear behind him as wide as a motorway, and as easy for anyone to follow if they wish.

Our use of technologies, and the use of technologies by governments and security services, have together made us all naked and conspicuous targets of the State's watchfulness. Thus, privacy has already gone: but that, Sofsky is quite right in implying, is no reason not to fight to get it back.

Until lately the citizen of a Western democracy was a private individual. In the name of a spurious security, and an unconsciously repressive ambition to achieve bureaucratic efficiency, Western democracies have thrown away the idea of “the private citizen”. Sofsky describes the new version of citizenhood, in which we live and have our being under the unblinking gaze of the State, showing how far-reaching is the invasiveness of a society whose bureaucracy and police puts everyone under suspicion all the time, by subjecting them to continuous tracking.

It is a picture by now almost too familiarly Orwellian, because from caricature to reality we have the example of the Gestapo, the KGB, the Party snoop, the informer, the spy, the jackbooted policemen stopping people to inspect their papers or administering the midnight knock on the door.

It is an almost ridiculous scandal that our own Westminster politicians, even as these words are being written, are introducing legislation requiring mobile phone and e-mail service companies to provide “the authorities” with a record of every call or message made by a British citizen. How do they fail to see any connection with the Orwellian nightmare, or understand the implications of making it come true?

It is a mistake, though, to think of privacy as solely a matter of externals in which one's purchase of toilet paper and one's visits to the doctor are collated on a database with one's bank account details and footage of walking about town. Privacy is about the person within, too, the space in which new ideas, anxieties, intimacies and hopes need protection from scrutiny for the wholeness of their owner's psychology.

Sofsky discusses how personal space can be violated and polluted by the invasions of others, as in being spat upon or exposed to the odour, sweat, flatulence and bad breath of others. Now think of those sullyings going to one kind of limit: being arrested, one's body taken over by policemen, handcuffed or bound, separated from everything normal in a bare cell into which a guard can look at will, barraged with impertinent questions. That is the end of the line at the end of privacy.

Bad people deserve no less, of course; but to place every citizen on a continuum with this, not merely with the potential for loss of privacy but the daily and hourly actuality of surveillance already happening, is to say that the State has turned sick.

There is a continuum too from the watchfulness of the ubiquitous security apparatus behind those swivelling CCTV cameras to the ultimate control - namely, of what people think and believe. Torquemada's Inquisition was one of many efforts made in the long history of tyranny to police people's minds. The confessional, and inculcation of the fear that one is being watched by the infinite and divine CCTV camera in the sky even when one is alone in the dark, was successful with the credulous and timid in medieval times, and remains so now among the superstitious.

But the State has given up on the idea of a patrolling deity, and has instead forested the streets with cameras, and the pockets of citizens with biometric data identity cards - for the same reason, and in hope of the same effect. For if people are afraid of that unblinking eye of surveillance, they will watch and then control their own thoughts - just what a certain type of State wants, and thus gets.

Sofsky ends with a discussion of this essential question of freedom of thought, for thought is the final privacy, and once it too has been brought under the State's scrutiny, the corpse of privacy has decayed beyond recognition.

This is an important and very timely book. Its message, implied throughout, is that as one of the great values of civilisation and one of the essentials of personal and psychological integrity, privacy is worth fighting to regain. If we were all to endorse this point, we would be halfway to achieving it.

Privacy: A Manifesto by Wolfgang Sofsky
Princeton University, £11.95; 160pp Buy the book here

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