The medium is the message, Marshall McLuhan famously said. And by changing the message we change ourselves. Never has this observation been so relevant as it is today, when many people spend their days at the computer, conducting friendships through Facebook and MySpace, posting videos on their websites, going into real society shielded by an iPod, or simply sending their avatar across the Grid in Second Life, looking for virtual relationships, virtual excitement and even virtual sex. Some welcome this, as a form of liberation. Shy people used to go trembling into society, hand in mouth; now they can go boldly into virtual society, hand on mouse.

But it would be naive to think people can live their lives this way, with their eyes on the screen and their minds on themselves, without affecting their capacity for real human relationships. Some might argue that we are witnessing a new kind of addiction. For addiction arises when something good but hard — in this case, friendship — is provided with a cost-free substitute, obtainable at the flick of a switch.

In real life, friendship involves risk. The reward is great: help in times of need, joy in times of celebration. But the cost is also great: self-sacrifice, accountability, the risk of embarrassment and anger, and the effort of winning another’s trust. Hence I can become friends with you only by seeking your company. I must attend to your words, gestures and body language, and win the trust of the person revealed in them, and this is risky business. I can avoid the risk and still obtain pleasure; but I will never obtain friendship or love.

When I relate to you through the screen there is a marked shift in emphasis. Now I have my finger on the button. At any moment I can turn you off. You are free in your own space, but you are not really free in mine, since you are dependent on my decision to keep you there. I retain ultimate control, and am not risking myself in the friendship as I risk myself when I meet you face to face. Of course I may stay glued to the screen. Nevertheless, it is a screen that I am glued to, not the person behind it.

You too, therefore, will not risk yourself; you appear on the screen only on condition of retaining ultimate control. This is something I know about you. And I know that you know that I know. And you likewise. There grows between us a reduced-risk encounter, in which each is aware that the other is fundamentally withheld, sovereign within his impregnable cyber-castle. I “click on” you, as I might click on a news item or a video. You are one of the products on display; but this does not make you an object of trust, with whom my life is mingled.

Second Life, which invites us to enter a virtual world through an avatar taken from its collection of templates, has more than 15m users. It provides opportunities for virtual business, virtual shopping, and even virtual “social” action, with social positions achieved by merit, or at any rate virtual merit. People can enjoy cost-free versions of the social emotions, and become heroes of “compassion”, without lifting a finger in the real world.

Of course, avatars are dolls, which must be ventriloquised by their cyber-parents. But the dolls are getting more realistic, and who knows, maybe soon they will be able to read each other’s body language, and begin to respond directly, presenting their watchful parents with moral dilemmas that they had never foreseen. The new “dream children” may soon possess all the attributes which their creators wish for but do not possess, and will be able to copulate in cyberspace with the dreams of other people, in a sterile caricature of erotic passion. On YouTube it is possible to see a film in which a couple who have never met describe their adulterous affair conducted in cyberspace, showing no guilt towards the victim, and proudly displaying their narcissistic emotions as though they had achieved some kind of moral breakthrough, by ensuring that it is only their avatars, and not they themselves, that ended up in bed.

Does this matter? I think it does. For trust, accountability and risk-taking are dispositions on which the future of society depends. And these things are learnt by accepting the real cost of them. They are not learnt by playing with their virtual substitutes, any more than real courage is learnt by playing with violent computer games. As people habituate themselves to living in virtual worlds where all is permitted and nothing is paid for, virtues like courage and justice will disappear, since nobody will have a need for them. Without those virtues, however, people will be unable to risk themselves in real encounters, and will hide instead in their narcissistic dreams. Some people look forward to this, hoping for a brave new world of virtual relationships; but surely the best thing about such a world is that no real person will be born there.