I was in Turkey, for various reasons. I was staying on Büyükada (the Big Island) in the Sea of Marmara, about twenty miles from Istanbul and the shining dome of Hagia Sophia. Once a place of exile for unruly princes, Büyükada later became a weekend retreat for Levantines, Europeans and the Ottoman upper classes. Remnants of this epoch are scattered all over the island, including a beautiful, decaying hotel called the Splendid Palace. No cars are allowed. People travel on foot, by bike or by phaeton – traditional horse-drawn carriages, driven by wild-eyed locals.

It’s always been a good place to write crazy works of fiction. George Gurdjieff lived by the harbour for a while. Leon Trotsky also lived on Büyükada after he was exiled by Stalin. He spent his days fishing and writing his self-aggrandising history of the Russian Revolution – as fictional as many novels. There’s a black-and-white photograph of him in his study reading The Militant, the newspaper of the Communist League of America. After a few years, Trotsky was on the move again: to France, Norway and finally Mexico.

One morning I asked around the neighbourhood and was shown to Trotsky’s house, a ruined mansion by the sea, its walls buried in bougainvillea. It is now the subject of a dispute and languishes in its post-revolutionary state. There is a high brick wall around the garden, but I scrambled over it and landed in a wild herbaceous border. Stepping over piles of rubble, I approached the house and pressed my face against a windowpane. Gloomy, abandoned rooms. Not the slightest trace of a samovar. Creeping away, I found an old iron frying pan in a bush. I took it home and cooked some eggs.

The following day I caught the ferry back to the city. The boat was quite empty, apart from a few elderly men drinking gallons of strong, sugary tea. I walked from the port towards Beyoğlu, passing the oldest hammam in the city (established in 1454, its slogan the ominous ‘We offer history not luxury’). Eventually I paused at a tall, narrow building on Cukurcuma Caddesi, painted the colour of a fine Merlot. This is Masumiyet Müzesi, or the Museum of Innocence, established by Orhan Pamuk in 2012. It contains an array of objects that Pamuk collected while writing his 2008 novel, also called The Museum of Innocence. The place resembles a Wunderkammer, though the true origins of the objects have been erased and we are told instead that the collection belongs to Kemal, the protagonist of Pamuk’s novel.

There are glass cases filled with lamps, books, clothing, thimbles, photographs of people in boats, shoes, earrings, ice cream cones, watches, newspaper articles, olive stones, bottles of cologne and shaving brushes, not to mention an annotated display of cigarette butts. From the top of the museum you look down on the entrance hall, where the floor is decorated with a spiral. An inscription reads, ‘If we can learn to stop thinking of life as a line corresponding to Aristotle’s Time, treasuring our time instead for its deepest moments, then lingering eight years at our beloved’s dinner table no longer seems strange and laughable.’ If time consists of moments, which shall we commemorate? The grand events, imbued with formal significance, or the quieter moments of love and surrender? In the novel, as in the museum, Kemal wants to ‘let everyone know, I lived a very happy life’. Except Kemal never really lived, so the museum also presents one more version of an old philosophical question: ‘What is reality anyway?’

As I walked back through Beyoğlu, I wondered why there aren’t more museums dedicated to fictional characters. We could have Orlando’s museum, richly adorned with the appurtenances of life through several centuries, as a man and as a woman. Or Raskolnikov’s bedroom, stinking of sweat, jeopardy and violence, or Krook’s junk shop, filled with bags of human hair. Perhaps that might not be much fun. How about a museum dedicated to the fictional author in Borges’s story ‘The Garden of Forking Paths’? This character decides it is not enough merely to describe a person’s life, from birth to death, so instead he writes about all the possibilities of a single life. Each time the path forks, the character takes every possible path; sometimes he is alive and sometimes he is dead. Everyone thinks the author of this unreadable novel has gone quite mad, but Borges’s story also makes a point about realism. All possibilities exist, at least potentially, so the truly realist novel must consider every single possibility. In the end you write something impossible: another crazy novel.

This month is the seventieth anniversary of the publication of Nineteen Eighty-Four by George Orwell. On my return from Istanbul, I found myself at the BBC recording a programme with Dorian Lynskey, Dr Lisa Mullen, Peter Pomerantsev and Matthew Sweet about the continued significance of Orwell’s vision. The discussion felt quite strange, as I recalled Trotsky’s mansion, with its view of the glittering ocean. Nineteen Eighty-Four is a savagely ironic novel, as readers will know. One particularly dark irony is that Winston Smith is initially consoled by the privacy of his own thoughts, by the fact that he inhabits a subjective reality that the Party can never change. However, as Smith is tortured, O’Brien explains that this is not the case at all: there is nothing except the mind of the Party and Smith must adapt his subjective reality accordingly. To illustrate his point, O’Brien holds up four fingers, claiming there are five, and carries on his interrogation until Smith sees five fingers. By then, we know he has been broken.

Under a tyrannical regime, only one version of reality is permitted, and if you diverge you may find yourself censored or imprisoned, as Pamuk discovered when he was put on trial for comments relating to the Armenian Genocide. It might be best, in that case, to present your thoughts as fragments in a small museum, subjective history or crazy fiction. Meanwhile, happy birthday to Nineteen Eighty-Four. Perhaps Winston Smith also needs his own museum. It could be called Room 101 and be an interactive, rodent-inspired experience, though this might deter visitors. Perhaps it could be a forest leading to a green valley, the place where Winston meets Julia, with lovely flowers, birdsong, and no sign of the thought police at all. That is, one more Museum of Innocence.