“The Book of Why- the New Science of Cause and Effect” by Judea Pearl and Dana Mackenzie

Judea Pearl is a professor of computer science at UCLA,  who has been working at the frontiers of machine learning and artificial intelligence for decades. Through this lens, he has become a leader in the new science of causation. Unbeknownst to many even in the disciplines that heavily rely on statistics, Pearl now believes that there has been a revolution in the techniques of teasing out cause from effect. In 2000, he proclaimed, “Causality has undergone a major transformation from a concept shrouded in mystery into a mathematical object with well-defined semantics and well-founded logic. Paradoxes and controversies have been resolved, slippery concepts have been explicated, and practical problems relying on causal information that long were regarded as either metaphysical or unmanageable can now be solved using elementary mathematics. Put simply, causality has been mathematized.” This book is Pearl’s effort to explain the science of causality in layman’s terms. He states that “the calculus of causation consists of two languages: causal diagrams, to express what we know, and a symbolic language, resembling algebra, to express what we want to know.” In this model, the data comes last because data is dumb to causal relationships.

The science of causation is so important because for humans “causal explanations, not dry facts, make up the bulk of our knowledge, and should be the cornerstone of machine intelligence…. Our transition from processors of data to makers of explanations was not gradual; it was a leap that required an external push…. Our ancestors’ capacity to imagine nonexistent things was the key to everything…. The connection between imagining and causal relations is almost self-evident.” The three levels of causation are “seeing or observing, [which] entails detection of regularities…. doing [which] entails predicting the effect(s) of deliberate alterations of the environment and choosing among these alterations to produce a desired outcome…. [and] understanding that permits imagining.” Therefore, Pearl has invented the metaphor of a Ladder of Causation, which consists of three rungs: association, intervention, and counterfactuals. Only the top two rungs involve causation. However, almost all animals and all current learning machines are stuck on the bottom rung. Intervention asks the question, “What if we do…? What Will happen if we change the environment?” Counterfactuals go back into time and require imagination. They ask, “what if things had been different?” This is skill, more than likely, unique to humans.

The bulk of Pearl’s book mixes the history of statistics with the history of a small set of outlaws, who dared to ask “why” questions, instead of just being content with correlations. Sewall Wright “was the first person to develop a mathematical method for answering causal questions from data, known as path diagrams…. [The path diagram] was the first bridge ever built between causality and probability, the first crossing of the barrier between rung two and rung one on the Ladder of Causation. Having built this bridge, Wright could travel backward over it, from the correlations measured in the data (rung one) to the hidden causal quantities.” As Wright himself wrote, defending his method from hostile attacks by the statistical establishment, “the combination of knowledge of correlations with knowledge of causal relations to obtain certain results, is a different thing from the deduction of causal relations from correlations.”

Pearl fully admits that causal diagrams require scientists to step out of their comfort zone of objectivity, explicitly. He states that “drawing a path diagram is not a statistical exercise; it is an exercise in genetics, economics, psychology, or whatever the scientist’s own field of expertise…. Causal analysis requires the user to make a subjective commitment. She must draw a causal diagram that reflects her qualitative belief—or, better yet, the consensus belief of researchers in her field of expertise—about the topology of the causal processes at work.” That is why Pearl came to causal science first through his work on Bayesian networks. “The prototype of Bayesian analysis goes like this: Prior Belief + New Evidence —> Revised Belief…. Bayesian statistics gives us an objective way of combining the observed evidence with our prior knowledge (or subjective belief) to obtain a revised belief and hence a revised prediction of the outcome…. To articulate subjective assumptions, Bayesian statisticians still use the language of probability…. The assumptions entering causal inference, on the other hand, require a richer language.” In causal diagrams, “each arrow can be thought of as a statement about the outcome of a hypothetical experiment…. Whereas a Bayesian network can only tell us how likely one event is, given that we observed another (rung-one information), causal diagrams can answer interventional and counterfactual questions.” The use of such diagrams allows the scientist ““provisional causality,” that is, causality contingent upon the set of assumptions that our causal diagram advertises…. They have the advantage of being conducted in the natural habitat of the target population, not in the artificial setting of a laboratory, and they can be “pure” in the sense of not being contaminated by issues of ethics and feasibility…. One of the major accomplishments of causal diagrams is to make the assumptions transparent so that they can be discussed and debated by experts and policy makers…. The diagram encodes the causal story behind the data.”

Pearl ends his book by circling back around to his expertise of machine learning and the state of the field today. He states, “With Bayesian networks, we had taught machines to think in shades of gray, and this was an important step toward humanlike thinking. But we still couldn’t teach machines to understand causes and effects…. Without the ability to envision alternate realities and contrast them with the currently existing reality, a machine cannot pass the mini-Turing test; it cannot answer the most basic question that makes us human: “Why?”” Machine learning will have to go beyond deep learning and gathering big data sets to get there. “In technical terms, machine-learning methods today provide us with an efficient way of going from finite sample estimates to probability distributions, and we still need to get from distributions to cause-effect relations…. A strong AI should be a machine that can reflect on its actions and learn from past mistakes. It should be able to understand the statement “I should have acted differently”…. Intent is a very important part of personal decision making…. The ability to conceive of one’s own intent and then use it as a piece of evidence in casual reasoning is a level of self-awareness (if not consciousness) that no machine I know of has achieved…. Thinking in terms of intents, therefore, offers us a shorthand to convert complicated causal instructions into simple ones…. The algorithmization of counterfactuals is a major step toward understanding these questions and making consciousness and agency a computational reality…. I believe that the software package that can give a thinking machine the benefits of agency would consist of at least three parts: a causal model of the world; a causal model of its own software, however superficial; and a memory that records how intents in its mind correspond to events in the outside world.”

“Conversations- Volume 3” with Jorge Luis Borges and Osvaldo Ferrari (translated by Anthony Edkins)

Borges never wrote a piece of fiction or poetry beyond twenty pages. These transcribed radio conversations show that he could pack a lot of weight into just a few words. The topics range from his own stories and poems, to gossip about his literary friends, to what it meant to be Argentinian, to Oscar Wilde and sodomy, to James Joyce dissecting the genre of the novel, to the defects of sociology, to Stoic philosophy, to Walt Whitman’s quintessentially American poetry, to the nature of time, and much beyond. Each self-contained broadcast is a joy in and of itself, but the collection shows the width and depth of Borges’ knowledge, while being relayed in his unique brand of ironic humor. Ferrari more than holds his own in the exchange of banter and pushes Borges both where he does and where he does not want to go. Although recorded in the 1980s, the themes and commentaries still ring relevant in today’s literary scene and geopolitical climate.

“The Story of the Lost Child” by Elena Ferrante (translated by Ann Goldstein)

This is the final novel of Ferrante’s Neapolitan quartet. Ferrante is a master of writing about the details of human relationships. At the heart of these four books is the enduring friendship and competition of two neighborhood girls, Elena and Lila. “I told myself again that she would no longer exercise any authority over me, that that long phase was over.” The quartet began when they were six years old, playing with dolls on the streets of Naples, and finally concludes with the narrator, Elena, as a grandmother living in Turin, but still tied to Naples, both to the city and to her childhood memories there. “A woman without love for her origins is lost.” The breath of this story deals with the mimetic rivalry between the two friends, where the hopes and dreams of the one become entwined with the other, whether in the realm of toys, school grades, the affection of lovers, their sense of purpose in the world, or the love of their families.  “She had dragged me into the swelling sea of her desires.” The two women, even with grown children of their own, constantly measure their own lives based on the success of the other. “From childhood I had given her too much importance, and now I felt as if unburdened. Finally it was clear that what I was wasn’t her, and vice versa. Her authority was no longer necessary to me, I had my own.” They compete for the praise of the same teacher. They fight for the charms of the same man. And by the time of this fourth novel, as both have matured into adults, each successful in their own way, they compete for the respect and admiration of their old neighborhood. “I had no doubts about how I would react if I discovered that she really had irrupted into my professional identity, emptying it.” This tight-knit lower class community has followed both of their lives and judged their successes and failures to its own idiosyncratic standards. “I loved my city, but I uprooted from myself any dutiful defense of it.”

“The Screwtape Letters” by C.S. Lewis

Lewis may be best known for his fantasy epic “The Chronicles of Narnia,” but he was also a devout Christian whose theological works such as “Mere Christianity” and “Reflections on the Psalms” dealt with his personal relationship with divinity and organized religion. In “The Screwtape Letters,” Lewis mixes fiction with his religious interpretations, writing as if an agent of the Devil who is giving guidance to a young co-conspirator trying to co-opt a man’s soul to the depths of Hell. The book is short, but densely packed and I found myself rereading many of the fictional letters over and over again. Strangely perhaps, it reminded me of Marcus Aurelius’ “Meditations” in that this book also tries to set down a guide to living a moral life, albeit a Christian, rather than a Stoic, one. The form of the book is entertaining and catching in the sense that one has to remember that it is the Devil’s agent giving the advice so one has to do the opposite to avoid being ensnared by the Devil’s traps. Lewis makes the case for an uncomplicated and personal piety away from the trappings of religiosity, while never outrightly condemning the established Church.

“Technocracy in America: Rise of the Info-State” by Parag Khanna

Khanna hammers away at a few simple points in this short book. Democracy is not the finality of all political progress. It is only a means, not an end in itself. The American system has a lot to learn from best practices in governance abroad. It needs to rely less on democracy and more on technocracy. Technocracy needs to be founded on a system of meritocracy. I do not agree with all of his diagnoses of the problems with American governance, not to mention his solutions, but Khanna has written a thoughtful book whose primary attributes are his boldness and fearlessness in solutions. No one can accuse him of not thinking outside the box. Still, the best parts of the book are where he dissects the best practices of other countries, rather than drawing up systems for America ex novo.

Khanna's two main models are Switzerland and Singapore. They both combine what he finds most appealing in direct democracy and technocratic management. Since 1848 Switzerland has held over half of all the world’s plebiscites. “With only 100,000 signatures, Swiss citizens can…. instigate national initiatives to propose new laws and even constitutional amendments, or referenda to challenge them.” Singapore has “scenario planners embedded in every ministry covering both domestic and international issues. These “foresight officers” organize and impartially frame scenarios for leaders to consider on an ongoing basis…. Scenarios are neither predictions nor straight-line projections, but are composites of emergent patterns that could combine into an integrated picture…. [Government] sets reasonable key performance indicators (“KPIs”) that are tracked at regular intervals to assess progress.” Khanna approves of the fact that the executive duties in Switzerland, Singapore, and China are shared, to some degree, by a committee rather than a single president. This divides oversight, responsibilities, and spreads out the leadership agenda. He also praises the Singaporean system where “all cabinet ministers are matched to permanent secretaries from the civil service who know the beat inside out. Singapore’s civil service is a spiral staircase: With each rung you learn to manage a different portfolio, building a broad knowledge base and first-hand experience…. Along the way, generalists become specialists and vice-versa, and cross-pollination leads to innovative problem-solving.” Singapore’s civil servants are also compensated well, among the best paid and most revered of its citizens.

Khanna favors changing America to a parliamentary system with no fixed election cycle and an executive chosen from among these MPs. This would be an executive committee of seven people. He also favors abolishing the Senate for dual-governorships, rotating between the state capital and Washington. This is all pie in the sky stuff, but Khanna exhibits a continual emphasis on administration, accountability, big data, empirics, trial and error, all mixed with plebiscites. He views the city-state as the unit of governance of the future. “The virtue of devolution is not only that distributing authority is as powerful a check on tyranny as democracy, but that it allows for local experiments and rapid citizen feedback, resulting in models that the federal government can further study and scale to other states.” His vision of America is an urban one, where cities connect with other cities, be they American or foreign, and in many ways bypass the gridlock of Washington. Meanwhile the federal government combines an administrative executive with a permanent technocratic bureaucracy, all checked by public referenda. That his America of the future will never actually become a reality doesn’t mean the Khanna doesn’t have some fresh ideas to debate.

“The Brothers Karamazov” by Fyodor Dostoevsky (translated by Richard Pevear & Larissa Volokhonsky)

This is a novel that deals with life’s biggest themes- filial bonds, sibling relations, God and the Devil, the honor of gentlemen, duty, respect, the purpose of life, free will, sex, love, and passion. The tale is full of intrigue and suspense. The three brothers Karamazov are so different and yet they seem to have a mystical bond that unites them. Their father is a degenerate, yet true to himself. The novel is particularly Russian, yet its themes transcend time and place. The plot is almost incidental to each character’s development. Almost all the individuals are fully fleshed out, with flaws and beauty in each. Dostoevsky does a particularly wonderful job plumbing the depths of what makes each brother tick, their internal struggles, and their code of life. The psychology of what makes us all human, how we relate to each other, and how we find purpose and meaning in life, both in this earthly world and in relations to a higher heavenly power, all come through. There is a current of mysticism that runs alongside an intensely religious pulse. The lessons are not didactic and yet Dostoevsky is seeking to expound eternal truths as he writes.

“The Iliad” by Homer (translated by Richmond Lattimore)

I had been meaning to read the Lattimore translations of Homer for a while now. He does not disappoint. I cannot read ancient Greek, so translation is the best I can do. I have read the Fagles, Pope, and Fitzgerald translations at different points in school, but almost every classicist I have spoken to speaks most highly of the Lattimore. The verse is a superb mix of keeping the poetry, while not taking liberties with the story. I cannot get enough of Homer and this was a great excuse to remember the tales of Hector and Achilles.

“In Search of Lost Time Vol. 1: Swann’s Way” by Marcel Proust (translated by C. K. Scott Moncrieff & Terence Kilmartin)

The narrator eats his madeleine dipped in tea. This is an epic length classic, told in such sustained detail and fervor. “Swann’s Way” starts with the narrator still in childhood. His recollections are priceless and his reflections insightful. It depicts a young boy growing up in Paris and the surrounding countryside in such intensely described vignettes that fascinate the mind. You see a changing aristocracy, an eccentric extended family, a loving mother, a detached father, and old servants still stuck in a disappearing formality. Proust’s words flow with such vigor and zest it is hard to tell where his own memory ends and where his imagination begins. No detail is missed. No thought left unexplained. Suddenly, we are swept away, back in time, into the world of Monsieur Swann, the narrator’s countryside neighbor. In this section of the novel the narrator remains in the background, as Swann’s tale begins years before his birth. Swann moves in the most notable and eligible of circles while in Paris, dining frequently with the Prince of Wales. However, it is intimated that he also has a disreputable side. Soon we hear of Swann’s passionate dalliance with Odette, a lady rumored to be of ill repute. What starts as a hot and heavy affair turns into a fractious relationship with Swann eventually maneuvered into the role of the spurned lover. Yet his attraction will not yield. The more he is tossed aside, the more his infatuation grows. He is consumed by his passion for Odette, even as he learns more and more of her notorious past. Proust relishes in giving every detail and intriguing morsel. Finally, the spell is broken and Swann’s consuming vigor passes. The love has finally faded. Or so we think, until the narrator starts up again, retelling the days of his own youth, and his own unrequited love affair with Swann’s daughter.

“Private Governance” by Ed Stringham

This is a good primer for anyone unaware of how the market can establish laws and regulations outside of a government framework. Stringham uses the example and analogy of private clubs that are able to form their own personal codes without the recourse to a monopoly of force. He then deals with the problems of negative externalities that often arise with public goods and how to best avoid free-rider problems. Much of the book details the rise of financial institutions that arose despite the lack of formal government laws and, in fact, sometimes, with laws that actually forbade them. Stringham recounts the formation of the first joint-stock companies like the United East India Company in 1614 Amsterdam. The Dutch government tried to prevent trading in stock-paper and especially short selling and futures contracts, but these inventions flourished nonetheless. Despite having no recourse to formal law, traders still acted honestly and fulfilled their obligations, for the most part. In London, barred from the main trading facilities for goods, stock traders formed their own private coffee houses, which eventually transformed into the City’s stock exchange. More controversially, perhaps, Stringham then goes on to detail how even brick and mortar services such as fire and police provisions have been provided by private parties when the government was unwilling or unable to adequately perform the task. The Patrol Special Police in San Francisco is just one modern example of private firms setting up where there was a demand that was not being met by public services. This private force was tailored to the demands of their clients, so whereas they prevented burglary and assault in San Francisco’s Chinatown, they were little concerned with the consensual acts of opium smoking and gambling. Stringham posits that absent government enforcement there would still be private law that evolves spontaneously, organically, and evolutionarily where and when the need occurs. Law can exist without legislation, but legislation rarely is enforceable when its contradicts civil society’s notion of law.

“Reasons and Persons” by Derek Parfit

This is one dense book of philosophy. It has many thought experiments and digressions that make it more bearable, but each page (and almost every sentence) has to be pondered over and reread to get the full depth of Parfit’s arguments. The beauty of this book is that it makes you reexamine your most cherished and basic beliefs. It makes you question the very essence of the Self and what makes you you. 

Parfit argues that humans would benefit from a new way of seeing the world. “Our reasons for acting should become more impersonal.” When viewing our own actions and weighing their morality it is often not enough to look at their effects in isolation. “It is true, of the act of each, that its effects on others are trivial or imperceptible. We mistakenly believe that, because this is true, the effects of our acts cannot make them wrong. But, though each act has trivial effects, it is often true that we together impose great harm on ourselves or others.” Actions often have imperceptible harms and benefits. It is better to be a rational altruist, who views it as irrelevant whether their acts perceptibly harm another.

Another area in which it behooves humans to be more impersonal is in relationships to their own children, family, and friends. “If we follow this impersonal principle, and give no priority to our own children, this will be better for all our children. Impersonality is again better, even in personal terms.”

Parfit considers effects logically and with numeracy. He takes into account probability and risk. “When the stakes are very high, no chance, however small, should be ignored. The same is true when each chance will be taken very many times.”

Parfit believes human morality should accept the Critical Present-aim Theory. “On this theory, the fundamental unit is not the agent throughout his whole life, but the agent at the time of acting. Though CP denies the supreme importance of self-interest through time, and of a person’s whole life, it is not impersonal. CP claims that what is rational for me to do now depends on what I now want, or value, or believe. This claim gives more importance to each person’s particular values or beliefs.” The reason this makes more sense to Parfit than a self-interest belief, which takes account of a person’s values throughout his life, is Parfit’s views on the nature of the Self. “We cannot explain the unity of a person’s life by claiming that the experiences in this life are all had by this person. We can explain this unity only by describing the various relations that hold between these different experiences, and their relations to a particular brain. We could therefore describe a person’s life in an impersonal way, which does not claim that this person exists…. Persons are not, as we mistakenly believe, fundamental.”

Parfit’s views on personhood do not imply a dismissal of the subjective world. “What are called subjective truths need not involve any subject of experiences. A particular thought may be self-referring. It may be the thought that this particular thought, even if exactly similar to other thoughts that are thought, is still this particular thought—or this particular thinking of this thought. This thought is an impersonal but subjective truth.”

However, Parfit denies the conception of the Further Fact of something like a Cartesian soul, ego, or any other type of mind/body dualism. “On the Reductionist View that I defend, persons exist. And a person is distinct from his brain and body, and his experiences. But persons are not separately existing entities. The existence of a person, during any period, just consists in the existence of his brain and body, and the thinking of his thoughts, and the doing of his deeds, and the occurrence of many other physical and mental events…. Personal identity just involves physical and psychological continuity. As I argued, both of these can be described in an impersonal way. These two kinds of continuity can be described without claiming that experiences are had by a person.”

Parfit also ruminates on how the ever-changing Self can affect love. “It may be clear to some couple that they love each other. But if they ask whether they are still in love with each other, they may find this question perplexing. It may still seem to them that they are in love, yet their behaviour towards each other, and their feelings in each other’s presence, may seem not to bear this out. If they distinguished between successive selves, their perplexity might be resolved. They might see that they love each other, and are in love with each other’s earlier self.” In fact, Parfit later suggests, “we can love, and believe we are committed to, someone who is dead. And the object of such love and commitment may be, not someone who is dead, but some living person’s earlier self.” This can be true because “we may regard some events within a person’s life as, in certain ways, like birth or death. Not in all ways, for beyond these events the person has earlier or later selves. But it may be only one out of the series of selves which is the object of some of our emotions, and to which we apply some of our principles.”

This view of the Self leads to Parfit’s views on morality and responsibility. “We no longer have the right to do whatever we like, when we affect only ourselves. It is wrong to impose upon ourselves, for no good reason, great harm…. These claims again give less importance both to the unity of each life and to the boundaries between lives…. I believe that what matters is Relation R, psychological continuity and/or connectedness…. This is what matters and the physical continuity does not matter…. On the Reductionist view, the unity of our lives is a matter of degree, and is something that we can affect.” We can affect this through the process of keeping a connectedness with our former selves as we age in our continual bodily process. “I want my life to have certain kinds of overall unity. I do not want it to be very episodic, with continual fluctuations in my desires and concerns. Such fluctuations are compatible with full psychological continuity, but they would reduce psychological connectedness.”

Parfit believes “that Relation R— continuity and connectedness— gives us a reason to be specially concerned about our own futures. This reason may not be as strong as the reason that would be provided by the Further Fact. And, because psychological connectedness is a matter of degree, we should reject the claim that it must be irrational to care less about some parts of our future.” However, Relation R, rather than the Further Fact, “makes me care less about my own future, and the fact that I shall die. In comparison, I now care more about the lives of others.” Parfit continues on death, “I believe that we ought not to be biased towards the future. This belief does not beg the question about the rationality of this bias. On any plausible moral view, it would be better if we were all happier. This is the sense which, if we could, we ought not to be biased towards the future. In giving us this bias, Evolution denies us the best attitude to death.”

Parfit makes the case that morality is simply a means and not an end in itself. “Compare two people who are trying to relieve the suffering of others. The first person acts because he sympathizes with these people. He also believes that suffering is bad, and ought to be relieved. The second person acts because he wants to think of himself as someone who is morally good. Of these two people, the first seems to be better. But the first person has no thoughts about the goodness of acting morally, or the badness of wrongdoing. He is moved to act simply by his sympathy, and by his belief that, since suffering is bad, he ought to try to prevent it. This person seems to regard acting morally as a mere means. It is the second person who regards acting morally as a separate aim that is in itself good. Since the first person seems to be better, this supports the claim that acting morally is a mere means.”

Parfit suggests that two of our moral beliefs can often compete and yet neither is intrinsically wrong. “We may have a pluralist morality in which we believe that it would be better both if there was greater equality and if there was a greater sum of benefits. There may then be cases where greater equality would lower sum of benefits. Our two principles would here conflict. But there would be no inconsistency in our moral view. We would merely have to ask whether, given the details of the case, the gain in equality would be more or less important than the loss of benefits.”

In the last section of his book, Parfit tries to tie his morality into a unifying theory through sheer effort of reasoning. He admits he does not fully succeed. He discusses some major unresolved problems at length. I will skim over some without doing justice to any. 

One is the Non-Identity Problem. The Time-Dependence Claim states that “if any particular person had not been conceived when he was in fact conceived, it is in fact true that he would never have existed.” Parfit goes on to debate what then we, in the present, owe to future generations. “Since these future people’s lives will be worth living, and they would never have existed if we had chosen [otherwise, any choice we do make] is not only not worse for these people: it benefits them.” In the future, the same people will not exist based on whatever choice we choose in the present. Should we then conclude about how our actions might affect the future, “since it will be bad for no one, our choice cannot have a bad effect?”

On morality, Parfit argues “it becomes more plausible, when thinking morally, to focus less upon the person, the subject of experiences, and instead to focus more upon the experiences themselves…. We are right to ignore whether experiences come within the same or different lives…. When we are trying to relieve suffering, neither persons nor lives are the morally significant units…. Suffering is compensated if it comes within a life that is worth living. If it comes within a life that is not worth living, it is uncompensated…. It is always bad if there is more uncompensated suffering. To this badness there is no upper limit…. The badness of this suffering cannot be reduced by the fact that other people are happy…. [However,] when there is more suffering only because there are more lives lived that are worth living, this extra suffering does not make the outcome worse.”

Parfit discusses his Repugnant Conclusion: “For any possible population of at least ten billion people, all with very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better, even though its members have lives that are barely worth living.”

Parfit contrasts his Absurd Conclusion: “In one possible outcome, there would exist during some future century both some population on the Earth that is like the Earth’s present actual population, and an enormous number of other people, living on Earth-like planets that had become part of the Solar System. Nearly all of the people on these other planets would have a quality of life far above that enjoyed by most of the Earth’s actual population. In each ten billion of these other people, there would be one unfortunate person, with a disease that makes him suffer, and have a life that is not worth living.

In a second possible outcome, there would be the same enormous number of extra future people, with the same high quality of life for all except the unfortunate one in each ten billion. But this enormous number of extra future people would not all live in one future century. Each ten billion of these people would live in each of very many future centuries.

On our view, the first outcome would be very bad, much worse than if there were none of these extra future people. The second outcome would be very good. The first would be very bad and the second very good even though, in both outcomes, there would would be the very same number of extra future people, with the very same high quality of life for all except the unfortunate one in each ten billion….

This conclusion followed from the asymmetry in our claims about the value of quantity. We placed a limit on quantity’s positive value, within some period, but we placed no limit on its negative value. To avoid the Absurd Conclusion we must abandon this asymmetry.

We cannot plausibly place a limit on quantity’s negative value. It is always bad if there is uncompensated suffering, and this badness never declines. We must therefore remove the limits on quantity’s positive value. When we remove this limit, we need a new way to avoid the Repugnant Conclusion.”

Parfit concludes, “because we can easily affect the identities of future people, we face the Non-Identity Problem. To solve this problem we need a new theory about beneficence. This theory must also avoid the Repugnant and the Absurd Conclusions, and solve the Mere Addition Paradox.

Since I have not yet found this theory, these conclusions are unwelcome. They undermine our beliefs about our obligations to future generations…. I believe that, though I have so far failed, I or others could find the principle we need…. But, before we have found solutions, we ought to regret this conclusion. With more unsolved problems, we are further away from the Unified Theory. We are further away from the theory that resolves our disagreements, and that, because it achieves this aim, might deserve to be called the truth.”