Privacy is a difficult subject. We react strongly when we consider our privacy violated, and privacy receives strong protection in law. The contentious U.S. Supreme Court judgement in Roe v. Wade affirmed the legality of abortion on the grounds that a woman’s body is private to her. “An Englishman’s home is his castle,” ruled Coke, prohibiting the King’s servants from inspecting the contents of our homes at their pleasure.

Recently an Englishman forfeited his holiday flight rather than allow the Queen’s servants to inspect his body in a scanner that would see through his clothes. Hundreds of other people accepted the same intrusion without comment if without enthusiasm. Clearly, people hold different views on the limits to privacy, and those differences have important consequences.

New technology poses new questions about what is private. Warrants are still required in Britain to intercept letters and telephone calls, but the state claims a right and the need to intercept the email messages that now largely replace letters, and to record whom we telephone and when. TV cameras record where we walk and drive. And IT has dropped the price of dossiers to the point where the previous government planned, in the form of the National Identity Register, to keep one on everybody, a plan the present government promised to kill but has so far failed to come to grips with.

A great difficulty in all this is the lack of an accepted theory of what privacy is and what rôle it plays in our society. Where we differ, feelings often run high, but we have no language, no theoretical framework in which to resolve our differences. Indignation and resignation confront each other, speechless but for polemic.

The weakest theory of privacy must tell what is at stake in issues of privacy, what is defended or attacked. A strong theory of privacy would add to this principles from which we can derive or set limits to privacy. What follows is the briefest sketch of a theory.

Privacy can usefully be viewed as the protection of hypocrisy. This is not a criticism of privacy. But the idea that hypocrisy should enjoy protection is so counter-intuitive that we must start by examining the rôle hypocrisy plays in our lives.

Famously, to err is human. Less famously, it is also human to lie. Our communities prosper according to how well we collaborate. But our personal shares in that prosperity depend on how well we compete. Collaboration requires moral individuals, who can make and keep promises, whose behaviour is governed by principles, loyalties and commitments rather than by whim and impulse. We all pretend to be such principled, responsible people, and from the moral and social world we conceal the personal lusts and ambitions it forbids. We are all, in this sense, liars.

This is not a matter for regret. It is within the privacy of our own skulls that we consult our own interests, and weigh against them the claims of others. This is the minimum condition of autonomy, the private space that ideology seeks to colonise, that Orwell’s Thought Police would patrol. Our existence as moral individuals is founded on an interior world free from scrutiny. This is the interior, private world that education develops.

I take care to stay on cordial terms with my neighbours. I keep to myself what I think about some of them. My public persona (persona from the Greek for mask) is a more agreeable and cheerful person for this hypocrisy. My hypocrisy serves my commitment. I am not committed to being bosom friends with my neighbours, merely to living peacefully with them.

My neighbours demand – in public – no more than John Wayne’s character in The Shootist: “I won’t be wronged. I won’t be insulted. I won’t be laid a-hand on. I don’t do these things to other people, and I require the same from them.” To expose my opinions, to criticise my neighbours in public, would have predictable consequences: justifications, counterattacks and demands for retractions and apologies until civility is restored.

Freedom from scrutiny is freedom from the demands of others. Inside my skull, wholly free from scrutiny, I think what I please. Inside my home, scrutinised only by friends I trust, I expose more of my thoughts than I will to my neighbours. As best I can, I protect my autonomy, my freedom of action, by controlling the scrutiny to which I am exposed. Just as you do.

It is much the same with corporations and governments. No one – individual or organisation – cares to be held to account and there can be no holding to account without scrutiny. The consequences of Shell’s oil spills in the Niger delta would be very different were they exposed to the scrutiny BP gets in the Gulf of Mexico.

Autonomy is an aspect of power. Individuals, corporations and governments require autonomy to function at all and generally seek to expand their power by reducing the scrutiny to which they are subject.

The alert reader can see where this is leading. MPs’ expenses, government interception of email traffic, leaks of U.S. diplomatic cables, hacking voicemails – all concern demands for scrutiny and resistance to it.

This is at least a weak theory of privacy. It tells us that privacy is immunity from scrutiny, an unsurprising conclusion. It asserts that all actors in society – individuals, corporations and the state – require some minimum of privacy, some freedom from scrutiny, in order to function at all. But it is not a strong theory of privacy. It gives us no guidance as to how much freedom the different kinds of actors should have.

My grandmother’s recipe for Christmas pudding may remain a family secret, but the makers of Kentucky Fried Chicken must list what goes into its “secret mixture of herbs and spices”. Up to a point, anyway.

That exact point, and the limits of different kinds of scrutiny, are always being renegotiated. Our theory does at least clarify why this is difficult to analyse. It finds no principle from which to argue any particular limit. Scrutiny limits power. In issues of privacy we see only a struggle between different classes of actors – individuals, corporations and governments – for power, and no grounds for supposing any particular settlement more enduring than another.

Usefully, our weak theory does offer a common language for discussing issues of privacy. Britain’s high-surveillance society, “sleepwalking into a police state”, has transferred power from citizens to state at an unprecedented rate. ‘Privacy’ might well occur to us as a luxury securocrats can frighten us into surrendering. Just possibly, ‘power’ is something the British people are less ready to concede.

These reflections were prompted by a lecture on 3 Feb 2011 by Prof. Michael Birnhack at the Institute of Advanced Legal Studies in London. Next week, we will be publishing Prof. Birnhack's reply.