Yet the living world is poised for a major evolutionary transition. Natural selection has thrown up a species able to self-edit its own genetic source code; phase out experience below "hedonic zero"; and engineer the well-being of all sentience in our forward light-cone. Intelligent agents will shortly be able to pre-select their own hedonic range: its upper and lower bounds, and hedonic set-points. Posthuman life can be animated by gradients of intelligent bliss - a default hedonic tone orders of magnitude richer than today's peak experiences.

Why Does Suffering Exist?

No one knows why suffering exists at all. To the best of our knowledge, unpleasant experience doesn't play any irreplaceable or computationally unique role in intelligent agents. Inorganic robots can be programmed or trained up to avoid and respond to noxious stimuli without undergoing subjective distress. Likewise, nonbiological machines can functionally replicate the role of our nastier core emotions without their "raw feels" - the ugly implementation detail that blights so many lives today.

Fortunately, solving the problem of suffering doesn't depend on our first solving the Hard Problem of consciousness. Neuroscanning and the tools of molecular biology are deciphering the "neural correlates of consciousness". If we use biotechnology to eradicate the molecular signature of experience below "hedonic zero", then on some fairly modest assumptions, phenomenal suffering becomes physically impossible.

So a practical question arises. Which existing psychological functions should we enrich, replicate or scrap? What kinds of function are best offloaded onto smart prostheses rather than biologically tweaked? Ideally, adaptations such as a predisposition to jealous behaviour might be abolished along with their nasty subjective textures. Such Darwinian traits have few defenders, even among bioconservatives. Other roles, notably nociception, will presumably be functionally essential for sentient beings to flourish for the foreseeable future - and perhaps indefinitely. Initially, preimplantation genetic screening of prospective children can ensure tomorrow's humans are endowed with benign, "low-pain" alleles of e.g. the SCN9A (1) gene to modulate pain-sensitivity. People blessed with high pain tolerance aren't vulnerable to the life-threatening information-processing deficits of congenital analgesia. Eventually, the avoidance of noxious stimuli can be offloaded onto smart inorganic prostheses, allowing life based entirely on information-sensitive gradients of bliss.



The Reproductive Revolution

Natural selection hasn't favoured a motivational architecture of gradients of bliss: it's "blind". Genetic mutations are effectively random; sexual reproduction is a crapshoot. As long as reproduction endures, some form of selection pressure is inevitable. But the nature of selection pressure is transformed when rational agents pre-select and customise the genomes of their future children in anticipation of the likely behavioural and psychological effects of their choices. Far-seeing "artificial" selection changes the rules of the game - in human and nonhuman animals alike. Selection pressure against traits scripted by our nastier code will intensify as the reproductive revolution gathers pace.

Clearly, "life events" matter hugely to each of us: genetic determinism is facile and simplistic. Genes and culture have co-evolved. Epigenetics, the heritable changes in gene activity not caused by changes in DNA sequence, and the purely conditional activation of different genes and allelic combinations "for" particular psychological traits, complicate the simple-minded storyline told here. Yet twin studies confirm that hedonic set-points - crudely, whether we are temperamentally happy or gloomy - have a high degree of genetic loading. More specifically, studies of e.g. the role of variant alleles of the 5-HTT serotonin transporter (2) ("the depression gene"); the COMT gene (3) (high versus low reward); and deletion variant of ADA2b (4) ("the pessimism gene") corroborate twin studies (5) of our heritable hedonic range. In an era of routine preimplantation genetic screening, prospective parents will presumably select code predisposing to emotional, intellectual and physical superhealth for their children in preference to disease and frailty.

It's unclear when selection pressure for a predisposition toward greater subjective well-being will plateau. Why settle for the mediocre when we can enjoy the sublime?

Credible modelling of the long-term trajectory of selection pressure in the post-Darwinian era is a formidable challenge. Yet it's not complete guesswork. Here a single example must suffice. Imagine you can use preimplantation genetic screening to choose, approximately, the hedonic set-point of your future child. What default hedonic tone would you pick? Oversimplifying, let's designate "minus 10" a predisposition to chronic severe depression; "0" to be hedonically neutral; and "plus 10" a predisposition to lifelong gradients of bliss. Informal straw-polling suggests a mean preference for "plus 7"s or "plus 8"s - with a perhaps surprising number of "plus 10"s. Today, depressives with sub-zero hedonic baselines form a significant minority of the population. A majority of people in the course of a lifetime cluster quite tightly either side of hedonic zero - with varying degrees of equability or emotional volatility. Either way, we needn't assume for the purposes of this thought-experiment that most parents care primarily about their children's happiness per se. For evolutionary reasons, many parents are intensely ambitious for their offspring. Other things being equal, psychologically resilient children tend to be "winners" - and more fun to raise too. So let's assume such anecdotal and impressionistic evidence is borne out by well-controlled studies. What hedonic dial-settings will these (super)happy children choose in turn when as parents-to-be they decide to have children of their own? In consequence of such individual parental choices - and perhaps top-down medical paternalism - default levels of subjective well-being will presumably be ratcheted upwards world-wide as the reproductive revolution unfolds later this century and beyond. Further genetically engineered reward pathway enhancements open up the prospect of an immensely richer hedonic ceiling and an elevated hedonic floor: true genomic rewrites rather than simple preimplantation screening. The negative feedback mechanisms of the hedonic treadmill can still play out; but on an exalted plane. The pitfalls are legion. So are the potential psychological rewards. Living in Heaven is fun.

When will the reproductive revolution take off?
Might traditional sexual reproduction predominate indefinitely?

Early in the twenty-first century, the use of genomic medicine to phase out terrible genetic disorders like cystic fibrosis or Tay–Sachs disease commands widespread but not universal assent. More controversial among bioethicists and prospective parents alike will be phasing out genes and allelic combinations predisposing to anxiety disorders and depression. In the West if not China (6), the spectre of coercive eugenics hangs over the debate. Critics of "designer babies" claim that misery and malaise are "part of what it means to be human". No doubt the critics are right. But low mood is at least as devastating to the quality of life of depressives as genetic disorders like cystic fibrosis. Depressive disorder causes almost a million people in the world to take their own lives each year.

Where should genetic remediation - or enhancement - stop?
The World Health Organisation (WHO) defines health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity."
Why not take the WHO definition literally?
As so defined, complete health can be secured only via post-genomic medicine.
Untreated humans would be prone to malaise in the Garden of Eden.

Rapid Genome Self-Editing

The reproductive revolution is potentially good news for our children and grandchildren. But what about existing humans? Like the prediction that medical science will deliver a cure for ageing shortly after your death, the possibility that our descendants may enjoy lifelong gradients of bliss can elicit mixed feelings. However, the CRISPR (7) gene-editing revolution heralds an era when rapid self-editing of your own genome can become the norm. Rapid genome self-editing promises radical enhancement options not just for our descendants but our future selves. And just as today using computers no longer entails writing low-level machine code, likewise powerful suites of user-friendly editing tools can revolutionise the user experience of genomic self-modification. The same is true of cybernetic self-enhancement. The smarter our artificially intelligent machines, the more effectively organic robots can edit our own biological wetware in a recursive cycle of self-improvement.



Why Recalibration Matters

Why not maximise happiness?

A venerable tradition in philosophical ethics, namely classical or "hedonistic" utilitarianism, bids us to maximise the happiness of the greatest number of sentient beings. For reasons we don't understand, the pain-pleasure axis seemingly discloses the world's inbuilt metric of (dis)value. Naturally, we don't know what intensities of bliss our distant successors may choose, or its guises; conceivably, posthuman superintelligence may opt for some kind of utilitronium shockwave propagating across the cosmos. In the meantime, we have abundant grounds for caution.

Two advantages of hedonic recalibration are worth noting here.

First, combining hedonic enrichment and recalibration ensures that critical insight, reinforcement learning, and social responsibility can potentially be retained while simultaneously massively enriching subjective quality of life. Recalibration undercuts the dilemma of hedonic enhancement as standardly posed. Should we choose gritty reality or an escapist fantasy world of self-delusion? The messy real world or Nozick's "Experience Machine"? Authenticity versus drug-addled life on soma? The Red Pill or the Blue Pill? And so forth.

Yet it's a false dilemma. We needn't choose between the Red Pill and the Blue Pill. Genetically enlightened agents can take the Purple Pill, so to speak, combining the benefits of realism and recalibration. For sure, mood-congruent cognitive biases are potentially a risk anywhere on the hedonic scale; without them, low mood might never have evolved in the first instance (8). But rose-tinted spectacles, so to speak, can be corrected with the tools of AI and decision-theoretic rationality. Genetic case-studies can also be conducted of contemporary high-functioning hedonic outliers, i.e. fortunate souls who are temperamentally "hyperthymic" but not manic. There's no evidence that traits such as empathy, intellectual prowess and virtues of character are less common in hyperthymics than depressives (9). What's clear is that other things being equal, life animated by happy experiences is appreciated as more valuable than a life of mediocre experience, just as mediocre experiences are more valuable than nastiness. Compare our appreciation of art, music or literature. If it's not rewarding, it's no good. Other things being equal, superhappy life is supervaluable too - subjectively at any rate: philosophers can endlessly debate its transcendental (in)significance. More informally, take care of happiness, and the meaning of life takes care of itself.

A second reason for embracing recalibration rather than happiness-maximisation is human cultural diversity. We're social primates; most of our preferences implicate others. Across the world, diverse people have diverse religious and secular value systems; and trillions of inconsistent and frequently irreconcilable preferences, trivial and profound. Theists and atheists, deontologists and utilitarians, virtue theorists and contractualists, pluralists and theory-scorning pragmatists dispute how best to live. Logically, let alone practically, there is no way to satisfy even the "idealised" preferences of liberals and conservatives, Christians and Muslims, jealous rivals in love - or fanatical Manchester United and Manchester City supporters. By contrast, reward pathway enhancements can radically enrich everyone's quality of life without forcing choices between "winners" and "losers": the zero-sum games endemic to Darwinian life. Recalibrating your hedonic set-point does not entail reducing neurodiversity, or buying into other people's utopias or their conception of the good life - unless of course you're opposed to the principle of recalibration itself. Hedonic enhancement can preserve whatever values, preferences and human relationships you hold most dear, while discarding states of mind you would gladly lose.

In practice, of course, the pleasures and preferences of posthumans may be humanly inconceivable.

Who Benefits?

Historically, the blessings of consumer capitalism have been enjoyed mainly by a privileged elite, slowly and erratically percolating socially downwards. Information-based technologies are different. The price of genome sequencing is collapsing. Preimplantation genetic screening is already more common in India and China than the West. The nature of information-based services is such that their price trends effectively to zero. Genomic rewrites will be cost-effective both ethically and financially. Thus the burden of depression, both clinical and subclinical, currently costs hundreds of billions of dollars each year to the global economy - quite aside from the misery of its victims. Critically, information-based services don't need to be rationed. For example, "counterfeit" genome-editing tools will be as inferior as "counterfeit" copies of Microsoft Word - an affront to intellectual property lawyers, no doubt, but not the bane of end-users.

The Rise of Full-Spectrum Superintelligence

Naively, a happy world is an intellectually stagnant world. Huxley's dystopian classic "Brave New World" shapes our preconceptions about universal bliss. In reality, the enterprise of knowledge has scarcely begun. Natural science can mathematically describe the formal, structural properties of the physical world with astonishing fidelity and predictive power. Yet first-person states of mind are an enigma. Drug-induced psychedelia (10) hints at the existence of immense state-spaces of consciousness as different as dreaming from waking: a tantalising mental terra incognita beyond the bounds of normal human experience. Alas at present exploration of psychedelia is unsafe to all but the most mentally robust psychonauts. The risk of nightmarish "bad trips" lurks within our dysfunctional reward circuitry. Hence the controlled status of psychedelic drugs in contemporary society - and lame a priori philosophising about consciousness in academia. A foundation of invincible well-being can inaugurate a future post-Galilean science of mind - a knowledge explosion to complement the happiness explosion.

The Plight of the Cognitively Humble

Human civilisation is based on an animal holocaust. Billions of incarcerated nonhuman animals suffer and die in factory farms and slaughterhouses each year. Their sentience and sapience is comparable to human infants and toddlers. Over the next few decades, mass-manufactured in vitro meat promises to replace the barbarities of factory farming. The technology of cultured meat products can amplify mankind's minimal and uneven benevolence to our fellow creatures.

More controversially, technology can accelerate the transition from harming to helping free-living sentient beings: mankind's fitfully expanding "circle of compassion". The civilising process needn't be species-specific but instead extend to free-living dwellers in tomorrow's wildlife parks. Every cubic metre of the biosphere will soon be computationally accessible to surveillance, micro-management and control. Fertility regulation via immunocontraception can replace Darwinian ecosystems governed by starvation and predation. Any species of obligate carnivore we choose to preserve can be genetically and behaviourally tweaked into harmlessness. Asphyxiation, disembowelling, and agonies of being eaten alive can pass into the dustbin of history.

Critics warn darkly of hubris. Yet Homo sapiens already "plays God": humans massively interfere with the rest of the living world. What's in question is whether we will act as callous or benevolent deities. Power breeds deepening complicity. It's hard to predict whether recognisable approximations of human or nonhuman Darwinian life will be preserved by posthumans. Perhaps we'll transform ourselves into post-Darwinian superbeings and consign primordial life to oblivion. In the meantime, an ethic of compassionate conservatism offers a compromise between the cruelties of orthodox conservation biology and the outright extinction of Darwinian life-forms. Free-living human or nonhuman animals do not lose some mysterious species-essence when they cease to be "wild"; on this score if no other, conservationists should sleep easy.



Suffering and Existential Risk

The problem of suffering and the problems of global and existential catastrophic risk (11) might seem tangential. In reality, maintenance of the biological status quo is hazardous to the prospects of civilisation and perhaps life itself. Evolution "designed" male humans to be hunters and warriors. The existence of suffering in a world of weapons of mass destruction presents profound global and existential catastrophic risks. Angst-ridden depressives, misanthropes, doomsday cultists and anti-natalists are more likely to believe sentience is a mistake and act accordingly. How many suicidal depressives would take the world down with them if the apocalyptic technology were to hand? A world of ubiquitous life-lovers is safer than a world full of smart but tormented Darwinians. Other things being equal, the more that intelligent beings love life, the more motivated we are to preserve it.

Paradise Engineering?

Other risks are more subtle. Imagine we stumble across an advanced civilisation that has abolished ageing, disease and unpleasant experience of any kind: a "Triple S" civilisation of superintelligence, superlongevity and superhappiness. The inhabitants enjoy lives animated by gradients of lifelong bliss. What arguments might human critics use to persuade its members to reintroduce involuntary suffering, predation, parasitism, ageing and the miseries of the ancestral past? The extraterrestrials would regard us as crazy: primitives in the grip of some kind of depressive psychosis.

Yet contrary to appearances, the advanced civilisation is guilty of one ethically catastrophic mistake. Its inhabitants have embraced the hedonistic imperative (12) too avidly and turned inwards too soon. They could have launched cosmic rescue missions for pain-ridden Darwinian life on Earth; and assumed responsible stewardship of the physical universe within their cosmological horizon.

In the real world, maybe we're alone. The skies look empty. Cynics might point to the mess on Earth and echo C.S. Lewis: "Let's pray that the human race never escapes from Earth to spread its iniquity elsewhere." Yet our ethical responsibility is to discover whether other suffering sentients exist within our cosmological horizon; establish the theoretical upper bounds of rational agency; and assume responsible stewardship of our Hubble volume. Cosmic responsibility entails full-spectrum superintelligence: to be blissful but not "blissed out" - high-tech Jainism on a cosmological scale. We don't yet know whether the story of life has a happy ending.

* * *

REFERENCES

1. Reimann. F. et al. "Pain perception is altered by a nucleotide polymorphism in SCN9A." Proc Natl Acad Sci U S A. 2010 Mar 16;107(11):5148-53. doi: 10.1073/pnas.0913181107.

2. Lykken, D., Tellegen, A. "Happiness Is a Stochastic Phenomenon." Psychological Science Vol.7, No. 3, May 1996.

3. Karg, K., Burmeister, M., Shedden, K., Sen, S. "The serotonin transporter promoter variant (5-HTTLPR), stress, and depression meta-analysis revisited: evidence of genetic moderation." Arch Gen Psychiatry. 2011 May;68(5):444-54. doi: 10.1001/archgenpsychiatry.2010.189.

4. Wichers, M. et al. "The catechol-O-methyl transferase Val158Met polymorphism and experience of reward in the flow of daily life." Neuropsychopharmacology. 2008 Dec;33(13):3030-6.

5. Todd R.M., et al. "Genes for emotion-enhanced remembering are linked to enhanced perceiving". Psychol Sci. 2013 Nov 1;24(11):2244-53. doi: 10.1177/0956797613492423.

6. Specter, M. (2014). "The Gene Factory: A Chinese firm’s bid to crack hunger, illness, evolution—and the genetics of human intelligence". The New Yorker, January 6, 2014.

7. Sander J.D., Joung J.K. (2014). "CRISPR-Cas systems for editing, regulating and targeting genomes". Nature Biotechnology. doi:10.1038/nbt.2842. PMID 24584096.

8. Sloman, L. (Ed.), Gilbert, P. (Ed.) (2000). "Subordination and Defeat: An Evolutionary Approach To Mood Disorders and Their Therapy". Routledge.

9. But see Jamison, R.J. (1996). "Touched with Fire: Manic-Depressive Illness and the Artistic Temperament". Free Press.

10. Shulgin, A. (1995). "PiHKAL: A Chemical Love Story". Berkeley: Transform Press.

11. Bostrom, N. (Ed), Cirkovic, M.M. (Ed). (2008). "Global Catastrophic Risks". OUP Oxford.

12. Pearce, D.C. (1995, 2014). "The Hedonistic Imperative". http://www.hedweb.com.