The title of David Eagleman’s book Sum, recently adapted by Wayne McGregor and Max Richter as an opera at the Royal Opera House, is no accident. Eagleman deliberately chose the term for three reasons: it is Latin for ‘I am’; it relates to the Latin term for a peak, or summit; and the author viewed the book as a whole to be greater than the sum of its parts.

The ‘parts’ are 40 individual pieces or vignettes, each of which stands alone, although all connect to the central thread of this fictional work, the possibilities for an afterlife, and the imagined experience of living after life.  It is therefore a purely speculative creation, in turn amusing, satirical, sad, poignant, and endlessly thought provoking.

We live in an era where the prospect of immortality is increasingly believed to be a possibility. By the late 1800s, life expectancy had significantly increased to over 40 years. By the end of the twentieth century, this figure had nearly doubled to 80 years, mainly due to improvements in hygiene and advances in medicine. Life can therefore be lengthened, perhaps even indefinitively, as transhumanists believe. They see death as a solvable problem, fuelled by advances in science and technologies, such as cryonics where you can be frozen on death, and revived at some point in the future when the technology allows it, or the possibility of uploading our ‘selves’ onto a computer, and becoming digital avatars when we die.  The impact of all of this, of these possibilities, is that the focus appears to have shifted away from the afterlife, a biblical Heaven and eternal paradise, and towards our perpetuation in this life.

Surprisingly few fictional works have the afterlife as their central theme. I have just read Shalom Auslander’s Beware of God stories. Auslander is Jewish, and draws on his faith to create stories that irreverently, and often hilariously, depict the afterlife. In one, God is a Big Happy Chicken, Yankel Morgenstein has a near death experience, where a brief sojourn in heaven brings the realisation that God is, yes, a large chicken. ‘Morgenstern thought of his wife and children down on Earth, praying uselessly to a non-fowl deity that didn’t exist.’ It is too much. Morgenstein wants to go back to Earth, and does.

As Eagleman and Auslander demonstrate, a fictional depiction of the afterlife is limitless in terms of what can be imagined and crafted. It is interesting that so few writers have chosen to explore the imaginative potential of a notion that has existed as long as man has. Death and the fear of non-being are conquered by most religious belief systems through physical resurrection.  The Nicene Creed professes: ‘We look for the resurrection of the dead and the life of the world to come.’ For Christians too, the weekly ritual of Holy Communion offers an explicit promise of immortality: ‘…if any man eat of this bread, he shall live forever.’ Resurrection, and the notion of paradise, is central to Abrahamic religions. In the Qur’an, paradise contains seven heavens, graphically depicted as places of spiritual and physical pleasure.

While today many continue to belong to various religious groups, surveys of believers have revealed that few accept the notion of a physical resurrection.

The strive for immortality continues, but it is infinite life on earth that now appeals.

The mortality paradox is one of the most prevalent of all paradoxes: we know we are going to die, but the fact of it is inconceivable and impossible. We cannot imagine life continuing in our absence. Thus, since the very beginning, humans have been driven by a search for immortality. Religion, with its concepts of Heaven, of resurrection and rising again, has at times satisfied this pursuit of immortality. But the satisfying – consoling, perhaps – capacity is waning, as our notion of immortality appears to have shifted to a desire for infinite life on this earth, and precludes the notion of an afterlife.

Eagleman includes Heaven and God in his afterlife possibilities. Heaven is by turn ‘a beautiful land of milk and honey’, with no starvation, poverty or war, with gardens of flora and fauna, angels with harps, and ‘San Diego weather’…and a place of blunders, where the bad go, with the good residing in Hell. God is a she, a married couple, a Frankenstein devotee, a species of ‘small, dim-witted, obtuse creatures’ searching for ‘the answer’, a multiplicity of beings.

The permutations are endless, and Eagleman, like Auslander, has fun playing with the possibilities, none of which can be disproved. Yet Sum strikes a serious note too. We humans are needy of meaning, so it is not surprising that Eagleman introduces a questioning into his stories. In one, he questions the meaning of death itself, stating that it is not one event, but three: when the body ceases to function, when the body goes to the grave, and when your name is spoken for the last time. The last is profoundly poignant, that moment of complete extinction, of non-being, or un-being, which goes beyond even a notion of legacy that the most devout of atheists may subscribe to.

Eagleman is a neuroscientist, and Sum at times reads like a conceptual experiment. At the beginning of each chapter, a set of conditions is laid down, which ultimately lead to consequences. Take for example the final story, Reversal. ‘There is no afterlife, but that doesn’t mean we don’t get to live a second time.’ The condition of living a second life is that we experience it backwards. Life rewinds. The consequences are that as it rewinds it also unravels. Your memory has spent its lifetime creating a mythology of who you are. As you journey backwards you realise that your life, and you, were a fabrication.

The chamber-opera adaptation is the result of a collaboration between Wayne McGregor and Max Richter. Although Eagleman was invited to co-write the libretto, he decided to leave it to the duo to experiment and craft a creation of their own. They chose 16 of the 40 original stories, a choice that Richter concedes may well reflect something of his own personal views. Richter believes that Sum is less about the afterlife, and more about this life and how we live it. The vignettes included in the performance reflect this. There is the afterlife where you relive your experiences on Earth, but reshuffled and like grouped with like. Thus, you spend seven months having sex, you sleep for thirty years, you experience all your pain at once…Or,  you can become the horse you always wanted to be, but only to realise that you forget what it was like to be your previous self, imagining what it would be like to be a horse…Or, the afterlife contains only people you know, there are no strangers. You feel sad, despite the realization that this was exactly how you chose to lead your life. Or, the afterlife is a place of multiple possibilities, and contradictions, all of which can be experienced at once, such as simultaneously listening and not listening, loving and hating… perhaps not so different from life as we live it, after all.

Eagleman, like Auslander and also reminiscent of John Updike’s short story Afterlife, has created a morality tale, a parable of sorts, which gently, and convincingly, hints that perhaps this life is not so bad after all. Make the most of it. We have no idea what, if anything, will follow.

The performance is both an opera and an installation, and the environment at the Linbury theatre, with seats removed, the orchestra in the pit, and images projected onto four walls, was hauntingly conducive to the chosen text, both sung and spoken. Richter’s music is beautiful, eerily so. It lingers, along with many thoughts and questions provoked by Eagleman’s text.

Eagleman calls himself a ‘Possibilian’. He sees possibility as the key message that the book contains. Having moved away from atheism, Eagleman believes in the potential and the possibility of life and of people, and of things we have never even considered.

Columba Quigley runs a blog on suffering and the arts