Tragic or comic, feathered or jewelled, Harlequin or Pierrot, all fiction is a masquerade.

We writers adopt disguises: we flirt, feign and play, and the story is the mask we wear. Behind every fiction, though, is fact. Behind every white page, the red of real life bleeds through.

My novel, A Love Letter from a Stray Moon, is a book of masks, partly about the Mexican painter Frida Kahlo (herself an avid mask-collector) and partly about the masked Mexican freedom-fighter, the Che Guevara of our times, Subcomandante Marcos.

The story is also a masque of motherhood. Frida Kahlo wanted a child but, as a result of her devastating accident, she could never have one, and the grief of this washes across her work. Yet her art can be seen as a substitute, creativity as masked motherhood. Her art is also a consolation for what she called the two great accidents of her life, one a physical accident which almost killed her and the other emotional, her devastating love for Diego Rivera. So many women find in Kahlo’s story a mirror of their own lives: passion, pain, love and blood. How does her story reflect mine? I can only tell you in metaphor, masked in moonlight.

A mask allows the wearer to say what otherwise they cannot, perhaps because of political fears or private reluctance. ‘Man is least himself when he talks in his own person,’ wrote Oscar Wilde. ‘Give him a mask, and he will tell you the truth.’ Truth is not the opposite of fiction: it is the fire at its heart. Fiction tells its truths slanted in metaphor and disguised with masks. But, crucially, the disguise discloses meaning: the mask unmasks deeper truths. In this, and in so many ways, the mask is a maestro of paradox. It covers and uncovers. It offers both shelter and licence. The mask can collapse space so the moon is within kissing distance, and can tumble time so a hundred years is yesterday, and the future is in our hands now.

They say that art mirrors life. I am interested in the way we artists can trick life into imitating art. I wanted to explore a singular grief in my life and to rewrite my own script. To transform grief to transcendence, turning bitterwater into wine.

Artists weave their past into their work, as Truffaut made his own childhood the subject of his films. Or artists may describe their present in their work, as Fellini famously did in his eight and a halfth film, Eight and a Half. With my book, I wanted to write my future: to write it in order to make it come true. If writing the past is an act of memory, and writing the present an act of confession, then mine is a spell. If you stencil your dreams on the walls, you can walk through them. Anyone can, though writers make their spells literal.

Masks have been used for spells, for prayers, for magic, ritual and serious healing across the world since time immemorial. Shamanism, the oldest religion, has often used masks in ceremony, to create the extraordinary time of mythic truths, to represent and to evoke the spirit of animals. The shaman may use the mask to ‘become’ an animal: it protects and strengthens the wearer and is an aspect of shapeshifting, that ancient metamorphosis.

The shamanic role is edgy, dwelling on the borders between the real world and the spirit world. The mask shares that quality of edge: the mask wearer is the transgressive El Clandestino, playing brinkmanship on the borders of identity. The famous Venetian masks often draw attention to their edges, tasselled, fringed and rimmed, and the traditional masquerade too has an illicit edge to it: rogues and lovers by twilight, at the edge of day and night. Shakespeare’s masked characters are border-crossers: boy-girls, girl-boys, the tender twinning of opposites at the edge.

The mask allows the wearer to be both more and less themselves, to take on a new persona in a flash: ventriloquism on a stick. In Frida Kahlo’s painting ‘La Venadita’ (The Little Deer,) she paints a hunted deer struck with arrows, and the deer has Kahlo’s own face as its mask. Her own experience, meanwhile, is masked in the injured, hurt animal. ‘Never before,’ said Diego Rivera, ‘had a woman put such agonized poetry on canvas.’ She made visible what many women know only invisibly: the intimate, internal catastrophe. A noiseless landslide. An unseen tsunami.

Mexico is famous for its masks and Kahlo – part indigenous Mexican herself – collected indigenous masks and Day of the Dead masks which, in the paradox of masks, are jaunty with life. She honoured her indigenous roots, wearing floor-length Tehuana dresses, and these served a second function, masking one of her legs which had been badly damaged by polio.

Mexican poet and essayist Octavio Paz portrayed Mexicans as living disguised, masked lives: of the Mexican, he writes: ‘his face is a mask and so is his smile… His language is full of reticences, of metaphors and allusions’. Behind the mask may lie deep wounds and resentments. No masked political reproach has been more eye-catching than Subcomandante in his trade-mark ski-mask, ironically the mask of the urban guerrilla, in his fight with the Zapatistas for the rights of the rural indigenous population.

Mischief-maker, poet and freedom fighter, Marcos is the most wanted man in Mexico. (I can well believe it: he, like Kahlo, are honoured between the sheets and, for the sake of public safety, it’s probably just as well they never met.) He is the public face – or mask – of a movement greater than the sum of its parts. The government wants to unmask him, to identify him as an individual, to reduce him to less than the sum of one part. But as it stands, his mask is a mirror, he says, to many. He mirrors the experience of a Palestinian in Gaza; an indigenous Papuan in Indonesian-occupied West Papua; he reflects the situation of a lesbian in Iran, a debt-ridden student in London, an unemployed woman in Melbourne, and an Aboriginal man in the Northern Territories. He elides all these roles: the mask allows it. We are all Marcos. Wearing a mask, one can temporarily eclipse one’s individuality and find a world of common cause, as masks unite people, universalized beneath disparate appearances.

If I take the mask of Marcos, it is because he is a rebel poet. If I take the mask of Frida Kahlo, it is because I understand a little of her life. If I take the mask of the moon, it is because she is a shadow-mother. The earth mothers things for real. Great, stonking, actual mothering in the major key. Just as truly – but in poetic truth played in the minor key – the moon mothers everything on the night-side. Metaphorically. And in the world of the masquerade, the moon may have a point of view about how the earth is treated, the moon a pale Pierrot gazing with love and sorrow at the Harlequin-earth. The moon can be a symbol of conscience for humanity: the moon’s purity an untouched goodness. The blank, moon-like masks of the Chorus in Greek tragedy played this role: speaking as the conscience of society, the Chorus could represent the ancestor-generations and the generations as yet unborn – much as masks may be used in environmental protest to demonstrate that activists speak for the deep future as well as the present.

Used for moral or political purpose, masks can distil meaning to its quintessence. They sharpen the focus on both the hideous and the ideal faces of humanity, as grotesque masks of Bush, Blair and Howard were used to protest against the Iraq invasion, while Burmese protesters hide their own faces behind beautiful masks of Aung San Su Kyi: her image giving them political inspiration while protecting them from identification. In the ‘Rebecca Riots’ in Wales, in the nineteenth century, the poor protested against high taxes and tolls, men dressed as women, answered to the name of Rebecca and wore masks.

Rebellion and subversion must often wear a mask to confront power, but for sheer comicality, my favourite political masquerade is the Clandestine Insurgent Rebel Clown Army (CIRCA). They take on the bulky solidity of the police at protests and defeat them in a merciless pillow-fight. With masking make-up and feather dusters, the clowns flirt, tease and pique curiosity. Like all masked marauders, they bewilder and confuse, they trip time with a banana skin and a wobbly plank, they wrong-foot their opponents and bewitch their friends: trick or treat.

Its burlesque quality comes from the tradition of Commedia dell’arte, with its masked characters, including Pierrot and Harlequin, the motley-wearing, amorous acrobat. But no mask tradition can be reduced to one source; the masquerade is an escapade – an escape from singular definition at every turn. It flies from pedantry, tickles the literal, it flirts with reality as fiction does.

Subcomandante Marcos not only wears masks but he writes in masked language, using fables, epigrams and riddles. He flirts with the moon, and she flirts back. He plays on words, illusive, allusive and elusive as those playful words suggest, he endlessly escapes definition with the leap of a sudden joke. Allegory, parables and symbols are also examples of masked communication and it is no surprise that people who experience severe political repression turn to these forms of language, where metaphor can take wing.

At the heart of all art is metaphor – flying from one thing to another – the winged language. Art has a quality of flight and masks demonstrate this: you can fly, with a mask, to another self. Feathers are an important part of the mask-making tradition, from shamanic masks to the masks of Venetian carnival.

So my book is a story of flight, from sere reality to poetic rebellion, and uses the masks of Kahlo and Marcos, because they are both tricksters from the mischievous world; dwellers in the mysterious domain; piratical, anarchic poets of the soul. Like all artists of rebellion, they defied destiny, in both personal and political terms. Lit by a ludic moon, they represent all that is subversive, enigmatic and elliptical in a magnificent starlit masquerade. I salute them. Unmasked.