Is this the sort of face that would launch a thousand untruths?

The group of SAS men who attended their recent press conference with their heads bagged up in balaclavas, and answering only to codenames, created a rare form of public appearance. It is the sort of public anonymity usually extended only to victims or to criminals. Everyone else is encouraged to show a face. If they won't, the general presumption is that they must have something to hide.

It is a doubtful presumption, but a strong one. Someone who voted at an election on the basis of a candidate's race wouldn't be voting sensibly. Yet a candidate who omitted their face from an election leaflet could well be suspected of withholding important information. And there are other examples of this tendency, rather closer to home.

The ancient study of physiognomy, of reading character from the face dies hard. Few people now will own up to the doctrine in its more rigorous, scientific form - observing firm rules for interpreting the length of a brow or the turn of a lip. The whole subject has been thoroughly discredited. But some adherence to the notion lingers on - and it seems to linger most stubbornly, even with increasing conviction, in the editorial departments of newspapers.

The outrageous, irrational and burgeoning practice of appending, to a piece of print, a picture of the writer's face, betrays an ineradicable faith in physiognomy. True, it is physiognomy of a very lay, commonsensical sort. But the general idea remains. If you put a face to a name, you supply some sort of extra and valuable knowledge about that person.

Of course, it is easy to believe this. You believe it, in spite everything that you know. You know, for example, that photography is very fallible, and can make someone look like anything. You know that faces are open signs, and that the same picture of someone's face, when you know them, looks quite different from how it looked when you didn't know them. A single picture of someone you don't know tells you almost nothing more. But the feeling persists: a face gives you a purchase on someone, opens them up to you. Exploiting that feeling is the basic gambit behind the use of writers' photos.

It is not only irrational. It is an outrage to the business of reading and writing. You don't need to have any high ideas about authorial impersonality or writing-as-mask to see that it could be an advantage, for writer and reader, if the printed word weren't continually inflected by whatever a face may communicate. Why should someone's apparent beauty, ugliness, age or youth stand as a point of cross-reference for their every word? Why should some frozen look of derangement, petulance, smugness, kindness, wisdom or affability constantly orient one's reading, as if each sentence bore the stage direction "smugly", "affably" etc?

It only results in a needless confusion of signals. The stern face makes a joke. The cheery face says something cruel. All kinds of complex and unnecessary over-readings follow. The words by themselves are not allowed to set their own tone - and yet a face of perfectly versatile neutrality is almost impossible to achieve.

Perhaps this protests too much. Writing 200 years ago, Johann Caspar Lavater, the father of modern physiognomy, made a telling point against his opponents:

"The majority of them - it is a mournful but a true remark - the majority are enemies of, because they dread the light of, physiognomy. I publicly declare that wicked men are in general its most determined foes. And what is the cause of this opposition? It is their secret belief in its truth. It is the conviction that they do not possess that exterior, which, were they good, were their consciences calm and undisturbed, they would possess."

They must have something to hide. And I admit there is a similar secret fear behind this argument: not precisely the fear of being known, by face, as a scoundrel; but the fear at least of being dangerously exposed. Your face is your hostage to fortune. No one is free of some betraying fault- line. We look at murderers' faces, scan them for tell-tale signs of murderousness and always find those signs. Physiognomy is infinitely resourceful. So with writers' faces, everything that may be dubious in their words will be focused on the face, read in to it, confirmed there - and thus redoubled in its dubiousness. That is the fear, and it is a rational one.

Still, it might be worse. There are many more telling keys to character than a face. If papers wished to make their writers better known, they could supply some of these too. A palm-print, a sample of handwriting, the time and place of birth; these would offer useful material to chiromancers, graphologists and astrologers. Medical and criminal records, family and educational history, sexual and voting habits, height, bodyweight, annual income; all this might be encrypted in a bar-code printed by a writer's name, with frighteningly instructive consequences.

Do we want to go down that road? No. If there must be identification, we have seen the future. Black balaclava. Codename: Rusty. Now, that would be perfect.

Thomas Sutcliffe is on holiday