Evgeny Morozov thinks that the Net had nothing much to do with what is happening in North Africa. This follows closely the conclusions of his book - "The Net Delusion: How Not to Liberate The World" - describing all the ways that authoritarians can use the Internet and turn it into a mechanism of control, and all the way that liberal states turn it into a depoliticising mechanism of entertainment. His up-bringing in Belorussia will have taught him a lot about how control societies work, and it is very good to have an observer like Morozov who really knows in his bones what truly authoritarian regimes are capable of.

Yet that deep insight of his also blinds him to another: an understanding of the conditions that make a moment transformational. The point about transformative moments - and they come in personal life as much as political life - is that they rely on reconfigurations of the assumptions of what Game Theorists call common knowledge.

Common knowledge within a group of people is the fact not only that something is known by everyone, but also that it is known to be known by everyone, known to be known to  be known by everyone, etc, ad infinitum. (There is an excellent Wikipedia article on common knowledge in Game Theory.) Knowing that something is commonly known is an important additional piece of information in many circumstances. What side of the road would you drive on if it weren't common knowledge what others would do?

It became a trope of the Bush era and the age of the military road to democracy promotion that what was really important to world affairs were the "unknown unknowns"; but it turns out that the real work in democratic transformations, the sort we hope is unfolding in North Africa and being brought to us by Wikileaks, is done by the "known knowns".

The extraordinary point of logic that the "common knowledge" assumption reveals is that a leap of faith is required - required in a logical sense - for risky, coordinated action to take place. If you like puzzles and you want to be quite sure that the sudden revelation of a "known known" can completely alter things, start with the classic example at the top of the Wikipedia article. The announcement of a piece of information that was already known but becomes commonly known has a completely transformative impact on a group.

But most cases are not so clear-cut - there is no deduction from the statement of common knowledge to the action; instead, there is the courageous decision to test whether everyone else - or enough others - are thinking what you're thinking. Jean-Jacques Rousseau, the eighteenth century Genevese philosopher credited - or blamed, depending on your view - with providing the underpinning for the French revolution described a stag hunt amongst a small group of people to illustrate the common knowledge problem. Hunting a stag requires a group of people closing in on the animal from afar in a gradually tightening circle. What stops a single person from going solo and coursing a passing hare rather than sticking to their position and closing in on the stag? As long as there is common knowledge that all others will stick to their allotted task, it makes no sense to course the hare. But absent that common knowledge, the hare becomes a temptation. Rousseau sees the solution of these sorts of problems as being at the origin of the invention of language and the social contract.

How does this apply to revolutions and the Internet? Hannah Arendt describes the transformative revolutionary moments in the histories of America, France, Russia and Hungary as being moments when ordinary people abandon their routines - when common assumptions about the way things go are thrown out - and people come together to invent a new way of doing things, a new set of common assumptions. These moments may not last, but they punctuate history and set the scene for real novelty in human affairs.

Now imagine what is needed for that moment of abandonment to actually occur. It requires a remarkable act of coordination. Instead of all the usual acts of routine coordination - when we get up, turn on the radio, go to work, pick up the children - a large group has to coordinate on abandoning the usual coordinating routine.

It is no surprise that the very simplest case, when it happens between just two people, has become the defining narrative of the liberal individual's life: the moment of attraction. I am sure you have had the experience - you catch someone's eye; you wonder whether they are thinking the same disruptive thought as you; you test the assumption by acting on the thought. When it works, it seems like a miracle: you made an assumption, took some risk and found something shared and new. This is why the story of falling in love is so central to our individualised worlds: it is the last place where we commonly experience that freedom of being joined together.

Franzen's Midwestern soap opera, Freedom, is an exploration of exactly these revolutionary moments in the personal lives of Americans. This is why the book deserves its grand title. Patty, the heroine, is the one who enslaves herself, who abandons freedom, because she refuses those moments of risk-taking and common knowledge. Her husband and then her son, surprisingly, do not. They live out their lives of freedom, even when it involves picking through their own shit to do so - quite literally in one marvellous moment of farce. "Freedom" is a modern exploration of the last adventure on the last frontier - the discovery of others, the moment of mutual risk-taking. "Freedom" describes the place that the American dream has created to keep the frontier alive. Morozov, like Patty, I feel, makes the error of ignoring the conditions which make mutual, social risk-taking not only possible but, more importantly, attractive.

Imagine extending the moment of action that everyone knows from courtship to millions of people. Computer science and networking theory has its own version of the common knowledge problem: the Two Generals Problem (again, there is an excellent Wikipedia entry). This shows that there is no communication protocol that will allow completely secure communication between two parties over a transmission channel that might be compromised or contain errors. If there is ever a worry that the message you got back contains an error - or worse has been tampered with - then no amount of confirmation of messages can guarantee that you will properly coordinate behaviour.

In the example of love, the "Two Generals" problem becomes the "shy lovers" problem: if each needs to know for sure that love will be reciprocated before making the first move, then love will never get off the ground. Love requires an act of faith, a willingness to be hurt, a being open to strangers whom you do not know that you can trust.

Web dating has transformed the creation of common knowledge amongst small numbers, and it is fundamentally in the very same process that lies the secret of the politically transformative nature of the web.

In the example of social protest, there is also a leap of faith - not the shy lovers, or the two generals, but the vulnerable first movers. When I go and put myself in danger, how do I know there will be safety in numbers? How does the Net affect the leap of faith? Not, as the Net Utopians whom Morozov rightly criticises might have it, by making truth and transparency by themselves powerful and indisputable agents. Rather, they make the leap of faith easier and less risky by providing a ground where alternatives can become commonly accepted. The Facebook groups, the Wikileaks cables, the blogs all show that any one person is not alone in a particular set of beliefs about the regime. Another form of common knowledge is allowed to take hold. It is not indubitable, and it may have been infiltrated, manipulated and it may in time be switched off - as has happened in Egypt. But the reality of the critique of the regime is believed to be commonly shared. That moment of catching someone's eye and deciding it is OK to act as if you are in the presence of a common soul has been moved online. In just the same way as dating sites have transformed the world of love, so social media have transformed politics: through the greater ease of making common knowledge. That is two arrows the web has sharpened: Cupid's and Freedom's.