Good post. Some further considerations on the total view side of things (mostly culled from a very old working paper I have here where I suggest life extension may be badâbut N.B. besides its age and a few errors, my overall view is now tentatively pro rather than tentatively con).
0. LEV or not seems to be a distraction. The population ethics concerns donât really change much either way if the offer on the table is LEV or merely âLâ (e.g. thereâs a new drug which guarantees lifespan to 150 but no more).
1. As the contours of your argument imply, I think the core ethical issue on totalist-y lights would be whether there is a âpackaging constraintâ on how one should allocate available lifetime to persons (e.g. better 1 800 year life versus 10 80 year lives, or vice versa), versus a broad cloud of empirical considerations and second order effects (although I think these probably dominate the calculus).
2. I donât buy the story that life extension can be a free lunch. If it is better to âpackageâ lifespan into 80 year chunks versus millenia-sized chunks, whether or not to pursue this will have great impact across the future, so any initial âfree benefitâ will be probably outweighed by ongoing misallocation across the future. (I suppose the story could be âLEV, even if bad, is inevitable, and doing it sooner at least gets a bigger free lunchâbut it seems in such a world there bigger scale problems to target).
3. On pure aggregation, the key seems to be whether lifespan has accelerating or diminishing marginal returns. As you say, intuitive survey by time-tradeoff gives conflicting recommendations: most would be averse to gambles like âWould you rather 5% chance of 2000 years (and 95% of dying right now) versus keeping your life expectancy?â, yet weâd also be averse to âLoganâs runâ (or Loganâs sprint) cases of splitting 80 year lives into 16 5-year lives (or, indeed, millions of 2 minute ones).
3.1 One natural reply to defuse âLoganâs runâ type reductios is to suggest it is confounded with human development. One might say our childhood and adolescence is in part an investment to enjoy the greater goods of adulthood. So perhaps we would take lifespan to have accelerating returns up commensurate to this, but maybe not for the interval of 20-ish to infinity (so if the returns diminish, there will usually be a break-even point whereby the âinvestment costâ is matched by the diminishing returns loss, so making the ideal tiling of lives across time not âas long as possibleâ.
(We should probably be pretty surprised if the morally âoptimalâ lifespan just-so-happened to match our actual lifespan which emerged from a mix of contingent biological facts. Of course, it could be the âoptimalâ lifespan is shorter, not larger, than the one we can typically expect.)
3.2 Thereâs a natural consideration for diminishing returns on the idea that people may naturally prioritise the best things to do with their life first, and so extending their lives gives them opportunity (borrowing a bit from Bernard Williams) to engage in further projects which, although good, are not as good as those they prioritised before then. So packaging into smaller chunks offers the ability for the population over the time to complete more âmost valuableâ projects.
3.3 On the other, thereâs a murkier issue about maybe having a much longer life âunlocksâ opportunities which are better than those shorter lives can access. In the same way âliving each day as your lastâ when taken literally is terrible advice (many things people want to do take much longer than a day to accomplish), perhaps (say) observing changes over cosmological or geological timescales are much experiences than what one can do in decades. This looks fairly speculative/âweak to me.
What seems more persuasive on the âincreasing marginal returnsâ side is the idea of positive interaction terms between experience moments. Some good things could be even better if they resonate with other previous moments, and so a longer prior life seems to provide further opportunity for this (e.g. insofar as âwatching the grandchildren grow upâ is joyful, a longer life better ensures this occurs, among many other examples).
4 Egalitarianism, âjusticyâ-considerations, or prioritarianism will generally push towards packaging in shorter blocks rather than longer ones: the one which best gets around tricky different number cases is prioritarianism. Insofar as you are sympathetic to these views, these will seem to push against life extension.
4.1: Iâm pretty sympathetic to Parfitian/âdeflationary accounts of personal identity, which would take the wind out of the sales of this line of argument (as there isnât much remaining sense of a given person being better or worse off than another, nor of an index to which thereâs a âyouâ that accrues person moments which may have diminishing returns). Such a view also takes the wind out of the sails of a pro life extension case (as we should be relatively indifferent to whether future moments are linked to our present ones or otherwise), although there might be second order considerations (beyond those mentioned above, if most experience moments simply prefer to be linked up to more future ones, this is a pro tanto consideration in favour).
5 It seems the second order impacts are best distinguished from the âpure axiologicalâ issue above. It could be that very long lives are an imperfect allocation, but still best all-things considered if (for example) it allows people to develop much greater skill and ability and (say) produce works of even greater artistic genius. A challenge to trying to disentangle this is plausible scenarios which offer (radical) life extension likely involve other radical changes to the human condition: maybe we can also enhance ourselves in various ways too (and maybe these arenât seperable, so maybe the moral cost we pay for improperly long lives is a price worth paying for the other benefits).
5.1 If we separate these and imagine some naive âeternal (or extended) youthâ scenario (e.g. people essentially like themselves, with a period of morbidity similar to what weâd expect now, but their period of excellent health extended by a long time), Iâd agree this leans positive. Beyond skill building benefits, Iâd speculate longer lives probably prompt less short-sightedness in policy and decision making.
Re 3â3.1: When discussing the marginal returns on a human life, a quantitative way of modelling human capability could be as the product of sigmoidal curves with positive and negative slopes to represent the scaling up of capability during development and scaling down of capability during natural aging. As long as aging doesnât kick in before development is finished then there is a plateau phase during which a person can perform at maximum capability and should produce constant returns on extra years in this phase.
Treating treating human capability as a single curve might be too simplistic. One could further break this down to intellectual and physical capability and intrinsic and extrinsic factors:
-Physical capability is simplest as humans probably reach peak intrinsic physical capability around 20 (sharp increase) and start to decline after 40 (slow decline). Iâm not sure there are extrinsic factors related to physical capability that will change as a function of a personâs life span.
-Intrinsic intellectual capability could probably continue to scale up for a long time with a slow increase (some luminaries may currently get close to peak intellectual capacity, but I suspect that most people alive at the moment donât) and this does not necessarily decline much during aging unless somebody gets an age related neurological disorder (which can cause a very sharp decline). While some might argue that people will keep increasing intellectual capability with age, Iâd argue that there probably is an upper limit to intrinsic intellectual capability given the brainâs capacity to store and process information (although neurotechnology may extend this). However, extrinsic intellectual factors like professional network size, strength, and value generally do continue to increase over time and could be modelled as a curve with a slow increase; while social network size currently tends to decline in old age this seems to be related to declining physical capability (reduced stamina limiting ability to socialize and forcing retirement) and so improving physical health during old ago may also prevent decline in some extrinsic intelectual areas.
Productivity could then be judged as weighted sums and/âor products of intrinsic and extrinsic intellectual and physical capability. The weighting will probably depend on the state of the society an individual lives and would change over timeâsubsistence farming would weight physical capability strongly, developed society initially favoured intrinsic intellectual capability but increased digital connectivity is increasing the value of extrinsic intellectual factors.
The reason I focus on a model composed of weighted sums/âproducts of sigmoidal curves of positive/ânegative slopes is that these can actually create fairly interesting results. The sum or the product of two sigmoidal curves with opposing slopes will be something like a bell curve (although it can be flat topped and have asymmetric sides), which probably agrees quite well with how people would judge the productivity of a current human life-span. However, having three sigmoid curves with the result depending on the product of two of them can create a local maxima before a later plateau, which could be used to represent an early peak in productivity due to physical capacity that will later be exceeded by intellectual capability (see this figure for an example I used of such a model https://ââwww.nature.com/ââarticles/ââsrep02614/ââfigures/ââ5 ). Also, sigmoidal curves are quite good at describing many biological processes.
In summary, the point Iâm getting at is there could be a good biological/âpsychological framework to discount life years based on both development and aging.
*Note that I donât have much experience in population ethics and am implicitly equating productivity to value and this may not be a good ethical framework (although I assume it will probably be agreeable to economists!).
Re 3.2: People also often do riskier things earlier in their lives. You donât see many 50 year old startup founders, maybe because they a more likely to need guaranteed income to to support their kids and/âor for retirement savings. But their greater knowledge and connections may give them a greater chance of success at high-risk/âhigh-reward type endeavours, and so LEV may allow people to undertake such promising activities later in life when they are better prepared for them.
Good post. Some further considerations on the total view side of things (mostly culled from a very old working paper I have here where I suggest life extension may be badâbut N.B. besides its age and a few errors, my overall view is now tentatively pro rather than tentatively con).
0. LEV or not seems to be a distraction. The population ethics concerns donât really change much either way if the offer on the table is LEV or merely âLâ (e.g. thereâs a new drug which guarantees lifespan to 150 but no more).
1. As the contours of your argument imply, I think the core ethical issue on totalist-y lights would be whether there is a âpackaging constraintâ on how one should allocate available lifetime to persons (e.g. better 1 800 year life versus 10 80 year lives, or vice versa), versus a broad cloud of empirical considerations and second order effects (although I think these probably dominate the calculus).
2. I donât buy the story that life extension can be a free lunch. If it is better to âpackageâ lifespan into 80 year chunks versus millenia-sized chunks, whether or not to pursue this will have great impact across the future, so any initial âfree benefitâ will be probably outweighed by ongoing misallocation across the future. (I suppose the story could be âLEV, even if bad, is inevitable, and doing it sooner at least gets a bigger free lunchâbut it seems in such a world there bigger scale problems to target).
3. On pure aggregation, the key seems to be whether lifespan has accelerating or diminishing marginal returns. As you say, intuitive survey by time-tradeoff gives conflicting recommendations: most would be averse to gambles like âWould you rather 5% chance of 2000 years (and 95% of dying right now) versus keeping your life expectancy?â, yet weâd also be averse to âLoganâs runâ (or Loganâs sprint) cases of splitting 80 year lives into 16 5-year lives (or, indeed, millions of 2 minute ones).
3.1 One natural reply to defuse âLoganâs runâ type reductios is to suggest it is confounded with human development. One might say our childhood and adolescence is in part an investment to enjoy the greater goods of adulthood. So perhaps we would take lifespan to have accelerating returns up commensurate to this, but maybe not for the interval of 20-ish to infinity (so if the returns diminish, there will usually be a break-even point whereby the âinvestment costâ is matched by the diminishing returns loss, so making the ideal tiling of lives across time not âas long as possibleâ.
(We should probably be pretty surprised if the morally âoptimalâ lifespan just-so-happened to match our actual lifespan which emerged from a mix of contingent biological facts. Of course, it could be the âoptimalâ lifespan is shorter, not larger, than the one we can typically expect.)
3.2 Thereâs a natural consideration for diminishing returns on the idea that people may naturally prioritise the best things to do with their life first, and so extending their lives gives them opportunity (borrowing a bit from Bernard Williams) to engage in further projects which, although good, are not as good as those they prioritised before then. So packaging into smaller chunks offers the ability for the population over the time to complete more âmost valuableâ projects.
3.3 On the other, thereâs a murkier issue about maybe having a much longer life âunlocksâ opportunities which are better than those shorter lives can access. In the same way âliving each day as your lastâ when taken literally is terrible advice (many things people want to do take much longer than a day to accomplish), perhaps (say) observing changes over cosmological or geological timescales are much experiences than what one can do in decades. This looks fairly speculative/âweak to me.
What seems more persuasive on the âincreasing marginal returnsâ side is the idea of positive interaction terms between experience moments. Some good things could be even better if they resonate with other previous moments, and so a longer prior life seems to provide further opportunity for this (e.g. insofar as âwatching the grandchildren grow upâ is joyful, a longer life better ensures this occurs, among many other examples).
4 Egalitarianism, âjusticyâ-considerations, or prioritarianism will generally push towards packaging in shorter blocks rather than longer ones: the one which best gets around tricky different number cases is prioritarianism. Insofar as you are sympathetic to these views, these will seem to push against life extension.
4.1: Iâm pretty sympathetic to Parfitian/âdeflationary accounts of personal identity, which would take the wind out of the sales of this line of argument (as there isnât much remaining sense of a given person being better or worse off than another, nor of an index to which thereâs a âyouâ that accrues person moments which may have diminishing returns). Such a view also takes the wind out of the sails of a pro life extension case (as we should be relatively indifferent to whether future moments are linked to our present ones or otherwise), although there might be second order considerations (beyond those mentioned above, if most experience moments simply prefer to be linked up to more future ones, this is a pro tanto consideration in favour).
5 It seems the second order impacts are best distinguished from the âpure axiologicalâ issue above. It could be that very long lives are an imperfect allocation, but still best all-things considered if (for example) it allows people to develop much greater skill and ability and (say) produce works of even greater artistic genius. A challenge to trying to disentangle this is plausible scenarios which offer (radical) life extension likely involve other radical changes to the human condition: maybe we can also enhance ourselves in various ways too (and maybe these arenât seperable, so maybe the moral cost we pay for improperly long lives is a price worth paying for the other benefits).
5.1 If we separate these and imagine some naive âeternal (or extended) youthâ scenario (e.g. people essentially like themselves, with a period of morbidity similar to what weâd expect now, but their period of excellent health extended by a long time), Iâd agree this leans positive. Beyond skill building benefits, Iâd speculate longer lives probably prompt less short-sightedness in policy and decision making.
Re 3â3.1: When discussing the marginal returns on a human life, a quantitative way of modelling human capability could be as the product of sigmoidal curves with positive and negative slopes to represent the scaling up of capability during development and scaling down of capability during natural aging. As long as aging doesnât kick in before development is finished then there is a plateau phase during which a person can perform at maximum capability and should produce constant returns on extra years in this phase.
Treating treating human capability as a single curve might be too simplistic. One could further break this down to intellectual and physical capability and intrinsic and extrinsic factors:
-Physical capability is simplest as humans probably reach peak intrinsic physical capability around 20 (sharp increase) and start to decline after 40 (slow decline). Iâm not sure there are extrinsic factors related to physical capability that will change as a function of a personâs life span.
-Intrinsic intellectual capability could probably continue to scale up for a long time with a slow increase (some luminaries may currently get close to peak intellectual capacity, but I suspect that most people alive at the moment donât) and this does not necessarily decline much during aging unless somebody gets an age related neurological disorder (which can cause a very sharp decline). While some might argue that people will keep increasing intellectual capability with age, Iâd argue that there probably is an upper limit to intrinsic intellectual capability given the brainâs capacity to store and process information (although neurotechnology may extend this). However, extrinsic intellectual factors like professional network size, strength, and value generally do continue to increase over time and could be modelled as a curve with a slow increase; while social network size currently tends to decline in old age this seems to be related to declining physical capability (reduced stamina limiting ability to socialize and forcing retirement) and so improving physical health during old ago may also prevent decline in some extrinsic intelectual areas.
Productivity could then be judged as weighted sums and/âor products of intrinsic and extrinsic intellectual and physical capability. The weighting will probably depend on the state of the society an individual lives and would change over timeâsubsistence farming would weight physical capability strongly, developed society initially favoured intrinsic intellectual capability but increased digital connectivity is increasing the value of extrinsic intellectual factors.
The reason I focus on a model composed of weighted sums/âproducts of sigmoidal curves of positive/ânegative slopes is that these can actually create fairly interesting results. The sum or the product of two sigmoidal curves with opposing slopes will be something like a bell curve (although it can be flat topped and have asymmetric sides), which probably agrees quite well with how people would judge the productivity of a current human life-span. However, having three sigmoid curves with the result depending on the product of two of them can create a local maxima before a later plateau, which could be used to represent an early peak in productivity due to physical capacity that will later be exceeded by intellectual capability (see this figure for an example I used of such a model https://ââwww.nature.com/ââarticles/ââsrep02614/ââfigures/ââ5 ). Also, sigmoidal curves are quite good at describing many biological processes.
In summary, the point Iâm getting at is there could be a good biological/âpsychological framework to discount life years based on both development and aging.
*Note that I donât have much experience in population ethics and am implicitly equating productivity to value and this may not be a good ethical framework (although I assume it will probably be agreeable to economists!).
Re 3.2: People also often do riskier things earlier in their lives. You donât see many 50 year old startup founders, maybe because they a more likely to need guaranteed income to to support their kids and/âor for retirement savings. But their greater knowledge and connections may give them a greater chance of success at high-risk/âhigh-reward type endeavours, and so LEV may allow people to undertake such promising activities later in life when they are better prepared for them.