I can think of seven reasons not to write a novel:

First: There are too many novels and too many people writing them. Not only do those already written continue to exist and demand to be eternally read, but thousands more entirely new novels keep appearing in publishers' catalogues and in bookshops around the world; then there are the many thousands rejected by publishers that never reach the bookshops, but which nonetheless exist. It is, then, a commonplace activity, one that is, in theory, within the grasp of anyone who learnt to write at school, and for which no higher education or special training is required.

Second: And precisely because anyone, whatever his or her profession, can write a novel, it is an activity that lacks merit and mystery. Poets, philosophers and dramatists do it; so do sociologists, linguists, publishers and journalists; politicians, singers, TV presenters and football coaches; engineers, school teachers, civil servants and movie actors; critics, aristocrats, priests and housewives; psychiatrists, university professors, soldiers and goatherds.

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It would seem, though, that for all its lack of merit and mystery, there is still something strangely alluring about the novel – or is it simply a desirable ornament? But what is so desirable about something that lies within the reach of all professions, regardless of their previous training, prestige or earning power?

Third: Writing a novel certainly won't make you rich: indeed, only one in every 100 novels published– and that's an optimistic percentage – earns a decent amount of money. The money earned is unlikely to change a writer's life and it certainly won't be enough to retire on.

What's more, it can take months or even years of work to write an average-length novel that some people then might want to read. Investing all that time in a task that has only a one per cent chance of making any money is absurd, especially bearing in mind that these days no one – not even aristocrats and housewives – has that amount of time to spare. The Marquis de Sade and Jane Austen did, but their modern-day equivalents do not; and worse still, not even the aristocrats and housewives who don't write but do read have time enough to read what their writing colleagues write.

Fourth: The novel is no guarantee of fame, or only a very minor fame, which could be acquired by far speedier and less laborious means. As everyone knows, the only real fame comes from television, where novelists are becoming an increasingly rare sight, unless the writer in question is there not because of the interest or excellence of his novels, but in his role as fool or clown, along with other clowns from various fields, whether artistic or not.

The novels written by that truly famous novelist-turned-TV-celebrity will merely provide the tedious and soon-forgotten pretext for his popularity, which will depend less on the quality of his future works, which no one really cares about anyway, and far more on his ability to wield a walking stick, wear stylish scarves or Hawaiian shirts or hideous waistcoats, and explain how he communicates with his unorthodox God or how easily and authentically one can live among the Moors (this always goes down well in Spain).

Besides, it would be nonsense to struggle to write a novel purely in order to become famous (for even if you write in the most pedestrian of styles, that, too, takes time) when nowadays one doesn't need to do anything very much to become famous. Marriage to or an affair with a suitably prominent person and the subsequent slipstream of marital and extramarital goings-on are a far more efficient way of going about it. Or you could simply commit some indecent act or outrage, although nothing, of course, that involves a long prison sentence.

Fifth: The novel does not bring immortality, largely because immortality barely exists any more. Nor, of course, does posterity, if one understands by that the posterity of each individual: everyone is forgotten once he or she has been dead a couple of months. Any novelist who believes otherwise is living in the past and is either very conceited or very ingenuous.

Given that novels last for, at most, a season, not just because readers and critics alike forget about them, but because only a few short months after a novel's birth it will have vanished from the shelves of bookshops (always assuming there are still bookshops), it's absurd, therefore, to imagine that our works will never perish. How can they possibly be imperishable if most of them have perished before they're even born, or have come into the world with the life expectancy of an insect? One can no longer count on achieving enduring fame.

Sixth: Writing novels does not flatter the ego, even momentarily. Unlike movie directors or painters or musicians, who can actually see an audience's reaction to their works and even hear their applause, the novelist never sees readers reading his book and is never there to witness their approval, excitement or pleasure. If he's lucky enough to sell a lot of copies, he might be able to console himself with a number, which, however large, remains just that, an impersonal, abstract number.

He should also be aware that he would share those same consoling sales figures with the following: TV chefs and their recipe books, gossipy biographers of feather-brained megastars, futurologists wearing chains, beads and even cloaks or jellabas, the poisonous daughters of actresses, fascist columnists who see fascism everywhere except in themselves, stuck-up fools giving lessons in manners, as well as other equally eminent scribes.

As for receiving glowing reviews, that is highly unlikely: if a novel does get reviewed, the reviewer may let the writer off lightly the first time, but not the second; or the writer may feel that the critic likes his novel for the wrong reasons; and if none of these things happens, and the praise given is overt, generous and intelligent, probably only about two people will read that particular review – a further source of upset and frustration.

Seventh: I will list here all the usual, boring reasons, such as the isolation in which the novelist works, his suffering as he wrestles with words and, above all, syntax, his fear of the blank page, his bruising relationship with major truths that have chosen to reveal themselves to him alone, his perpetual stand-off with the powers-that-be, his ambiguous relationship with reality, which can lead him to confuse truth with lies, his titanic struggle with his own characters, who sometimes take on a life of their own and may even run away from him (although the writer would have to be somewhat of a coward for that to happen), the vast amount of alcohol he consumes, the special and basically abnormal life you have to lead as an artist, and other such trifles that have seduced innocent or foolish souls for far too long, leading them to believe that there is a great deal of passion and torment and romanticism in the rather modest and pleasing art of inventing and telling stories.

This brings me to the one reason that I can see for writing novels, which may not seem much in comparison with the preceding seven, and which doubtless contradicts one or another of them.

First and last: Writing novels allows the novelist to spend much of his time in a fictional world, which is really the only or at least the most bearable place to be. This means that he can live in the realm of what might have been and never was, and therefore in the land of what is still possible, of what will always be about to happen, what has not yet been dismissed as having happened already or because everyone knows it will never happen. The so-called realistic novelist, who, when he writes, remains firmly installed in the real world, has confused his role with that of the historian or journalist or documentary-maker.

The real novelist does not reflect reality, but unreality, if we take that to mean not the unlikely or the fantastical, but simply what could have happened and did not, the very contrary of actual facts and events and incidents, the very contrary of "what is happening now". What is "merely" possible continues to be possible, eternally possible in any age and any place, which is why we still read Don Quixote and Madame Bovary, whom one can live with for a while and believe in absolutely, rather than discounting them as impossible or passé or old hat.

The only Spain of 1600 that we know and care about is the Spain of Cervantes: the Spain of an imaginary book about other imaginary books and out of which an anachronistic knight errant emerges, rather than out of what used to be or was actual reality. What we call the Spain of 1600 does not exist, although one has to assume that it did; just as the only France of 1900 that exists for us is the one Proust decided to include in his work of fiction.

Earlier, I said that fiction is the most bearable of worlds, because it offers diversion and consolation to those who frequent it, as well as something else: in addition to providing us with a fictional present, it also offers us a possible future reality. And although this has nothing to do with personal immortality, it means that, for every novelist, there is the possibility – infinitesimal, but still a possibility– that what he is writing is both shaping and might even become the future he will never see.

© Javier Marias

Translation © Margaret Jull Costa

Reprinted with permission from The Threepenny Review, Summer 2014; threepennyreview.com

Javier Marias has had his work translated into more than 40 languages; his most recent novel is 'The Infatuations', now published in paperback (Penguin, £8.99). Margaret Jull Costa has been his translator since 1992