Mrs Mortimer's odyssey was truly remarkable - between 1849 and 1854, she published three volumes of travel writing, covering Europe, Asia, Africa and the Americas, each larded with her own special brand of disdain. The Portuguese “the clumsiest people in Europe”; the Welsh “not very clean”; the Zulus “a miserable race”.

Favell Lee Mortimer held her Victorian readers spellbound with her colourful descriptions of foreign lands and their benighted inhabitants. But what made Mrs Mortimer's attitude to foreign countries even more extraordinary was that she had never been to any of them. Mrs Mortimer wrote her entire travelogue from her drawing room in England. Apart from a childhood trip to Paris and Brussels, she never set foot outside this country and had no wish to - already convinced, as she was, that abroad was full of all those clumsy, unhygienic and unhappy foreigners.

Mrs Mortimer's spiritual heir is the former Lonely Planet writer Thomas Kohnstamm, who cheerfully admitted this week that he had written a section of the Colombia guide without having visited the country. Bogus travel writing has a long and inglorious history, but in another way Kohnstamm is representative of a wider and more modern malaise: writers reviewing books they have not read, politicians claiming to have braved dangers they never faced, novelists depicting places they have not seen, memoirists describing a past that never happened, journalists making up stories about people that never existed, and, most pernicious of all, writers simply cutting and pasting words they have not written.

In most cases this is not active deception, but rather a strange cultural blurring of truth and fiction, the confusion of first-hand knowledge with second-hand electronic cuttings, the elision of personal experience with a reality borrowed or imagined from elsewhere.

This is the victory of information over experience. In Wiki-world, where so much semi-reliable information is available at the push of a button, there is no need to see something first-hand in order to be able to describe it with conviction and authority. A comparison of Paris guidebooks reveals entire chunks of identical text for some tourist spots: why actually visit somewhere to find out what it is like when one can merely paste together a version of reality?

Hillary Clinton's embarrassed writhings after it was revealed that she had not actually come under sniper fire in Bosnia in 1996 are emblematic of this strange melding of fact and imagination. In her own mind Mrs Clinton did not lie, or even exaggerate, but rather “misspoke”. Appropriating the broader reality of a situation for political gain was nothing more than a “minor blip”.

At all levels of the culture, the ability to spin a good yarn is valued more highly than its veracity. Novelists, of course, can make up whatever they like, but I could not help feeling oddly cheated to discover that Stef Penney, the prize-winning author of The Tenderness of Wolves, had set that novel entirely in Canada without ever seeing the place.

Far more damaging is the spate of misery memoirs depicting various degrading aspects of human behaviour - drug addiction, alcoholism, abuse, poverty - that are really novels, or at best novelised reality.

Even more worryingly, it seems that most readers do not really care whether the horror is true or not: voyeurs would rather not know that the whole thing is merely an act, a simulacrum of reality.

The plagiarism of words is a familiar crime, but the plagiarising of experience is something more subtle, and far harder to detect. “I never read a book before reviewing it,” declared Sidney Smith. “It prejudices a man so.” There is now an entire literary subculture devoted to the art of not-reading books, but pretending to have done so.

In his recent book How to Talk about Books You Haven't Read, the professor of French literature Pierre Bayard offered a complete guide for literary charlatans.

OK, I admit that I have not read all of Professor Bayard's book, but what I did read was both ironic, in that slightly baffling French way, and deeply depressing, since it accepted as axiomatic that no one would ever want to read a challenging book for pleasure when a six-word crib, or a quick skim, will do the trick.

There is even a new word for this sort of fakery: “truthiness”. Coined by the American television comedian Stephen Colbert, truthiness describes anything that a person claims to know intuitively without regard to actual experience, evidence or the facts. In Colbert's words: “We're not talking about truth, we're talking about something that seems like truth - the truth we want to exist.” When Mrs Clinton remembered dodging the bullets in Bosnia, she was indulging in truthiness, adopting an experience she wanted to be true.

Whenever a politician claims to be speaking “from the heart”, he or she is likely to be expressing truthiness more than truth. The row over James Frey's partly invented memoir A Million Little Pieces was an object lesson in truthiness, and the danger of melding fact and fiction.

When Thomas Kohnstamm wrote about the sights of Colombia without seeing them, his descriptions were not exactly untrue, merely exercises in truthiness. Does it need to be said that there is no substitute for reading the book, or describing the beauties of Colombia from first-hand? A non-fiction memoir that tells the truth, rather than a truth the author has wished into words, packs an emotional punch that is the equal of the greatest fiction.

Mrs Mortimer's crime was not just to be an armchair travel writer who imagined a world she never visited; it was not just that she saw that imaginary world through a thick veil of ignorance and prejudice. Mrs Mortimer's problem was that by relying on truthiness, she managed to get her view of the world consistently, vividly and hilariously wrong.

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