There are few ideas more mind-blowing than that of the multiverse, and the notion that the universe is perpetually dividing into parallel universes, each of them containing versions of ourselves.

Long before I’d ever heard of the multiverse, or parallel universes, I was pretty much obsessed by the notion that every decision I took led to an outcome, or rather, a series of outcomes, which, had I chosen differently, would have led to different life circumstances – not just for me, but for others around me. To use a footballing analogy, one of the things that used to bother me was when a sports commentator would say ‘if he hadn’t missed that goal in the first half, the score would now be 2-1’ No!! If he hadn’t missed that goal something else would have happened, and then something else – every moment of the game would have unfolded in a totally different way from the way it did by the missing of the goal; just as in life, if I had stayed behind one night in 1984 for another drink, or had worn another shirt, or had stepped into the road, or had decided to take the bus rather than the tube, the course of my life would probably have been different. True, the outcomes might often be trivial, but they might also, on the other hand, be life-altering. The term ‘sliding-door’ moment has become shorthand for this line of thinking.

I remember a story about a small boy I knew, let’s call him Francesco, who, as a five-year-old asked his grandmother: ‘where will little Francesco be when I am a grown up?’ The question is staggering in its perspicacity. It is as if the child had intuited the possibility of multiple selves emerging at every step of the way on his journey towards adulthood; which in turn suggests a precocious anticipation of the multiverse.

Hugh Everett, a Princeton PhD student, published a thesis in 1947 that introduced the concept of the multiverse. In it, he claimed that we are living in a multiverse of countless universes, in which exist countless copies of ourselves. Each decision in the course of a life precipitates the splitting of the universe, which then continues to split, infinitely, with each decision that follows.

At the time, Everett’s theory was rejected by the then reigning authority in quantum mechanics, Niels Bohr, and Everett, disgusted by academia, gave up theoretical physics and went to work for the Pentagon as a probability analyst. However, among a small group of followers his theory lived on, took on momentum, and is now seriously regarded by many of today’s leading quantum physicists as foundational. According to one of these physicists, Max Tegmark of MIT, Everett’s discovery of the multiverse is ‘as important as Einstein’s work on relativity.’

The idea that at each and every turn the cosmos divides into parallel universes in which every conceivable outcome of every event happens somewhere is both appealing and terrifying. On the one hand, there is some comfort, to me at least, in knowing that all the bad decisions I ever took have – in some distant world – been counteracted by better ones. On the other hand, there is the moral dilemma of whether or not one is causing suffering in other universes by making certain choices which will, by definition, have negative ramifications elsewhere in the multiverse, with potentially disastrous consequences. After some deep thought, I came to the realisation that – as Rowan Hooper put it in a New Scientist article on the theme: ‘the best way to live in the multiverse is to think carefully about how you live your life in this one.’

Writers who have been inspired by the multiverse since the 1960s include Philip K. Dick, Diana Wynne Jones, Stephen King, Phillip Pullman and Neil Garman. However, all of these writers made use of the trope of the multiverse, or parallel universes after Hugh Everett’s discovery. Not so J.L. Borges, as I was alerted a few weeks ago by an article in the Spanish newspaper El País.

Readers may remember Borges’ story, ‘The Garden of Forking Paths’ (El jardín de los senderos que se bifurcan), which is the account given by one Yu Tsun, a German spy working in England during World War One. Dr Tsun, who is Chinese, is being pursued by a British agent named Richard Madden, who is Irish, a detail that already suggests divided loyalties. Dr Tsun has information of great importance to the German war effort, but with Madden closing in on him, is unable to pass this on to his masters in Berlin. He goes, inexplicably, it seems, to the house of Dr Stephen Albert, a renowned Sinologist with a special research interest in Ts’ui Pên, Tsun’s grandfather, a respected sage, who retired as Governor of Yunnan Province in order to write a vast novel and ‘to create a maze in which all men would lose themselves. He spent thirteen years on these oddly assorted tasks before he was assassinated by a stranger. His novel had no sense to it and nobody ever found his labyrinth.’ It turns out, this being Borges, that the book and the labyrinth are one and the same thing, and the title of this infinite and ‘chaotic novel’ is of course, The Garden of Forking Paths.

Albert tells Yu Tsun that Ts’ui Pên’s novel is modelled on a maze in the sense that it constantly bifurcates ‘in time, but not in space.’ ‘In all fiction’, he explains, ‘when a man is faced with alternatives he chooses one at the expense of the others.’ However, in this novel, whenever a course of action has to be decided upon, rather than choosing one and pursuing its linear development, each course taken divides in two, with each of these being the point of departure for other, further, bifurcations, and so on.

‘Your ancestor (continues Albert) . . . believed in an infinite series of times, in a dizzily growing, ever-spreading network of diverging, converging and parallel times. This web of time – the strands of which approach one another, bifurcate, intersect, or ignore each other through the centuries – embraces every possibility. We do not exist in most of them. In some you exist and not I, while in others I do, and you do not, and in yet others both of us exist. In this one, in which chance has favoured me, you have come to my gate. In another, you, crossing the garden, have found me dead. In yet another, I say these very same words, but am an error, a phantom.’

After this peregrination towards the mysteries of the multiverse, it almost comes as an anti-climax to learn that the only reason Yu Tsun has decided to come to this house is to murder Albert, whose name will be splashed all across the newspapers the following day – thereby informing Yu Tsun’s spy chief in Berlin that Albert is the name of the northern French town from which the Allies are preparing a massive artillery offensive against the German lines.

The publication of Borges’ story predates the theory of multiple universes, as devised by Hugh Everett, by six years. A neat illustration of art anticipating science, perhaps, but also, as my own intuitions have led me to think, and young Francesco’s observation put into startling perspective, not entirely unusual or unprecedented: perhaps, as with the language faculty, we are somehow hard-wired to acquire this knowledge; perhaps we already know it.