A theory that tells you to make things go best is not yet a theory until it says what "best" means, and every candidate answer has a case that breaks it.
The previous lesson left the good as pleasure, which is where Bentham left it and where Mill already found it untenable. This lesson works through the three families of answer, then turns to a harder problem the theory of the good cannot avoid: adding welfare up across people, and deciding how many people there should be. The population arithmetic is the part most readers have never seen, and it is the part that does the most damage.
Hedonism and the experience machine
Hedonism says that what is good for a person is pleasure and the absence of pain, and nothing else. It has the virtue of being about something everyone recognises from the inside, and the vice of being refutable by one thought experiment.
Robert Nozick, in Anarchy, State, and Utopia in 1974, asks you to imagine a machine that gives any experience you want. Floating in a tank, electrodes on your skull, you would believe yourself to be writing a novel, making a friend, reading a book. Others can plug in too, so nobody need be neglected. You can preprogramme a lifetime. From the inside it would be indistinguishable from a wonderful life. Would you plug in?
Most people say no, and if hedonism were true there could be no reason to refuse, since the machine delivers strictly more pleasure than any real life. Nozick draws out what the refusal reveals: we want to do things, not merely to have the experience of doing them; we want to be a certain sort of person, and someone floating in a tank is not anything; and we want contact with a reality deeper than what we can construct. Each of those is a value that hedonism cannot accommodate.
The honest qualification is that the intuition is less clean than it looks. Felipe De Brigard reported in 2010 that when subjects are instead told that they have been in a machine all their lives and can now leave, most choose to stay, and that adding an unattractive real life increases the preference for staying further. That suggests a large part of the standard reaction is status quo bias rather than a perception of value. The result does not rescue hedonism, since even a modest residual preference for reality is one hedonism cannot explain, but it does mean the case should be cited as evidence rather than as a demonstration.
Preference satisfaction
The natural repair is to stop asking what feels good and start asking what people want. A person's life goes well to the extent that their preferences are satisfied, whatever those preferences are about.
This fits economics, which measures preference through choice, and it respects people's own authority over their lives. It also handles the experience machine immediately: you prefer that your friendships be real, that preference is not satisfied in the tank, so the tank is worse for you even though it feels the same.
Three problems follow it. The first is preferences whose satisfaction never touches you. You want a stranger you met once on a train to recover from her illness; she does, and you never learn of it. Did your life go better? Something has to be said, and both answers are awkward: yes makes welfare depend on events with no connection to the person at all, and no forces a restriction to preferences about one's own life that is hard to state without circularity.
The second is misinformed and malicious preferences. Someone wants a drink that is poison. Someone else wants their neighbour to suffer. Counting these at face value gives absurd results, so the theory is normally refined to satisfaction of the preferences one would have if fully informed and rational. That helps, and it moves the theory towards the objective view, because the idealisation is now carrying the weight and the question is what makes an idealisation the right one.
The third is the hardest, and it comes from development economics. Amartya Sen documented that people in long deprivation report themselves satisfied: a woman with no education in a society that permits her none may sincerely prefer things as they are, and health surveys find the chronically ill in poor regions reporting less morbidity than better-off people with milder conditions. Martha Nussbaum built her capabilities approach around exactly this. If welfare is preference satisfaction, adaptive preferences make oppression invisible, since the oppressed adjust their wants downwards until they are met.
Example. A hospital must choose between a treatment that leaves patients pain-free but with reduced memory, and one that preserves memory at the cost of chronic moderate pain. Patients split. What does each theory of welfare say?
Hedonism gives a determinate answer: compare the aggregate pleasure and pain, and the pain-free option almost certainly wins, since memory loss is not itself painful. Preference satisfaction says there is no single answer, since which is better for a patient depends on that patient's preferences, and it makes the split rational rather than a sign that half of them are confused. An objective list theory says that memory and continuity of self are components of a good life independently of whether the patient wants them, so it can say that some patients are choosing wrongly, which is either its great strength or its great weakness depending on your view of paternalism. The example is worth holding on to because it shows the three theories are not equivalent formulations: they give different clinical advice.
Now you. A man raised in a rigidly hierarchical society sincerely prefers not to be educated and reports himself content. Which theories can say his life is going badly, and on what ground?
Answer
Hedonism cannot, so long as he is content, and this is a strong argument against it. Simple preference satisfaction cannot either, since his preferences are met. Informed-desire versions can, by asking what he would want if he knew what education makes possible, and this is the move that does the work, though it needs an account of idealisation that does not simply insert the theorist's values. Objective list theories can say so directly, holding that understanding and autonomy are components of a good life whether or not they are wanted, which is Nussbaum's position and the reason she prefers to speak of capabilities, what a person is actually able to do and be, rather than of what they have or want. The cost is the charge of paternalism, and the standard reply is that a capability is an opportunity rather than a requirement, so the theory demands that he be able to be educated and not that he be educated.
Objective lists
The third family says there are things that make a life go well whether or not they are wanted and whether or not they are pleasant. Derek Parfit set out this three-way division in an appendix to Reasons and Persons in 1984, and it has been the standard map since.
Typical lists include knowledge, achievement, friendship and love, autonomy, aesthetic experience and health. The theory's advantage is that it says the obviously right thing about the machine, about the deprived man, and about the person who spends a talented life counting blades of grass, which Rawls used as a test case.
Two objections. The first is that the list is unargued: any item can be questioned, and the theory has no principle generating them, so it looks like the theorist's own preferences promoted to metaphysics. Defenders reply that the list is arrived at by reflective equilibrium like everything else, and that the convergence across very different traditions on roughly the same items is evidence rather than coincidence.
The second is alienation, and Peter Railton stated it best in 1986: something cannot be good for a person if it leaves them entirely cold. A life of achievement that its owner finds hollow is not going well for them, whatever the list says. The usual response is a hybrid: an item counts towards a person's welfare only when they engage with it, so that the good life requires both the objectively worthwhile activity and the subjective endorsement of it. Most contemporary theories are hybrids of this kind, which is a sign of health rather than of confusion.
Adding it up
Whatever the good is, consequentialism has to sum it across people, and that requires welfare to be measurable on a scale where one person's gain can be compared with another's loss.
Nothing guarantees that. Ordinal preference, the kind economics is built on, tells you that I prefer A to B, and says nothing about by how much, and nothing at all about whether my gain from A exceeds yours from B. The interpersonal comparison the theory needs is an extra assumption, and Lionel Robbins argued in the 1930s that it is not scientific at all.
Practice proceeds anyway, and the results are not absurd. Health systems use the quality-adjusted life year, a year of full health scored at 1 and a year in a given health state scored between 0 and 1 by surveyed valuations. The National Institute for Health and Care Excellence in England has for two decades used a threshold in the region of 20,000 to 30,000 pounds per quality-adjusted life year when deciding what the health service should fund. That is interpersonal comparison, done officially, with a published number attached, and a system that refused to do it would still be making the comparison implicitly and worse.
So the practical objection is weaker than the theoretical one. What survives is that the comparisons are rough, contested, and much less precise than the arithmetic they feed, which should make anyone suspicious of an argument whose conclusion turns on a small difference in the sum.
Example. A quality-adjusted life year scores a year in a given health state between 0 and 1, using values obtained by asking survey respondents how much healthy life they would trade to avoid the state. What does that method assume, and where does it go wrong?
It assumes that a health state has a single value, that people can report it reliably, and that the reports of the general public are the right input. Each assumption has a known failure. People who have lived with a condition consistently rate it far less badly than people imagining it, a robust finding often called the disability paradox, so the choice of whose valuations to use changes the answer systematically; using the public's values discounts the lives of disabled people, and using patients' values risks the adaptive preference problem from earlier in this lesson. The method also treats a year of life as equally valuable to everyone, which is what makes the arithmetic possible and is itself a substantive moral choice, since it implies that saving a year for a young person and for an old one count the same while a life-extending treatment for the young buys more years. None of this makes the measure useless; it makes it a moral instrument rather than a measurement, and the practical response has been to publish the valuation method rather than to abandon the exercise.
Now you. Two treatments cost the same. One gives 20 people an extra year each in a state valued at 0.5. The other gives 5 people an extra year each in full health. Which does the arithmetic favour, and what does the comparison hide?
Answer
The first gives quality-adjusted life years and the second gives , so the arithmetic favours the first by two to one. What the comparison hides is everything about distribution. It is silent on whether the 20 are already worse off than the 5, on whether either group has any other option, and on whether a state valued at 0.5 for a year is a year that its occupant is glad to have, which is the welfare question the rest of this lesson has been about. It also hides the fact that the value 0.5 came from a survey rather than from the patients. A decision maker who reports the ratio without those caveats has produced a number that looks like a measurement and is really the output of a chain of moral choices, and the honest use of the figure is as one input among several.
Population, and the conclusion nobody accepts
The worst problem in the theory of the good is not about individuals at all. It is about how many of them there should be, and it was Parfit who made it inescapable.
Total utilitarianism says to maximise the sum of welfare. Then consider a world A of ten billion people, all with excellent lives, and a world Z with a hundred thousand times as many people, each of whose lives is barely worth living: some music, some potatoes, and nothing else. Set the good life at 100 units and the barely-worth-living life at 0.01. World A totals . World Z totals , ten times as much. Total utilitarianism says Z is better, and by a wide margin.
Parfit called this the Repugnant Conclusion, and the mere addition paradox shows it is not easily escaped. Start with A. Add a separate group of people with lives clearly worth living but less good, without affecting anyone in A: this seems no worse, since nobody is harmed and the added lives are worth living. Now level the difference and share the resources, raising the worse-off and lowering the better-off with a net gain in total: this seems better. The result is a larger world with lives slightly less good than A's. Repeat, and each step is defensible while the destination is Z.
Switching to the average view avoids Z and buys worse problems. On the average view, adding a person whose life is worth living but below average makes the world worse, so a happy child born to very happy parents is a moral cost. The same view produces what Gustaf Arrhenius called the sadistic conclusion: where adding lives below the average is bad, it can be better to add a small number of people with lives of suffering than a large number with lives that are worth living but modest. And it makes the value of an act depend on people long dead, since they are in the average.
Arrhenius has proved a series of impossibility theorems showing that no population axiology can satisfy all of a short list of very plausible adequacy conditions. This is not a defect of utilitarianism specifically. It is a result about the structure of any view that ranks outcomes containing different numbers of people, and it is why the area is unsettled rather than merely difficult.
Example. Compute the totals for A and Z above, and say precisely which premise of the mere addition argument you would deny.
The totals are and , so Z beats A by a factor of ten. To resist, you must deny one of three things. That adding people with lives worth living, harming nobody, cannot make an outcome worse: denying this means holding that a world can be made worse by the existence of a person glad to exist. That a more equal distribution with a higher total is better: denying this means rejecting either the priority of the worse off or the value of totals, at least in this application. Or that "better than" is transitive: denying this is drastic and some philosophers, including Larry Temkin, have accepted it precisely here. There is no comfortable option, and the standard of a good answer in this area is knowing which discomfort you have chosen.
Now you. A critical-level view says only lives above some positive threshold add value, so lives just barely worth living count negatively. Does that solve the problem?
Answer
It blocks the Repugnant Conclusion and generates a new one. If lives below the critical level make the world worse, then a world of people whose lives are worth living but modest is worse than an empty world, and worse than a world of the same size in which those people suffer slightly more but are fewer. That is the sadistic conclusion again in another dress. The general pattern, which Arrhenius's theorems make precise, is that every escape route from the Repugnant Conclusion is paid for elsewhere, and the useful conclusion for a reader is not despair but calibration: an argument whose force depends on comparing outcomes with different populations is standing on the least secure ground in ethics, and should be discounted accordingly. Arguments about climate policy and about existential risk both stand there, which is why they are unusually hard to settle.
The separateness of persons
One objection cuts across every version of the theory of the good, and it is the deepest.
Nozick, in the same book as the machine, imagines a utility monster: a being that derives enormously more welfare from any resource than anyone else does. Total utilitarianism says everything should be given to it, and everyone else should be sacrificed to its pleasures. The example is fanciful, and its point is structural. A theory that ranks outcomes by a sum has no way of objecting when the sum is maximised by a very unequal distribution, because the sum is blind to who holds the terms.
Rawls put the same charge without the monster in A Theory of Justice in 1971: utilitarianism does not take seriously the distinction between persons. It extends to society the principle of choice appropriate for one person, in which a present sacrifice for a future gain is straightforwardly rational, and in doing so treats separate people as though they were phases of a single life. My suffering can be compensated by your pleasure only if there is somewhere for the compensation to land, and there is not.
This is the objection the lesson on what we owe each other develops into a rival theory. Before that, the theory faces a set of more immediate embarrassments: cases where maximising the good requires an act that almost everyone regards as monstrous, and a level of demand that no life could sustain. That is the next lesson.