Manipulating the distribution of lifespans

Suppose that you have the power to alter people's lifespans, but only on a statistical basis, not person by person. Perhaps you can do this through genetic engineering, or through putting something in the water supply. (As is normal in philosophical thought experiments, we shall not worry about practicalities.) Furthermore, you cannot ask people's permission before acting, and you are the only person in the world who can take this action.

To be precise, you can take, or refrain from taking, action that will have the following effects. The effects are only on offer as a single package: you cannot pick and choose selected effects.

A. The mean of the distribution of life expectancies for the affected group will rise.

B. The dispersion of that distribution will fall, but the overall shape of the distribution will remain unchanged. If, for example, the distribution was normal, it will remain normal, but with a lower standard deviation. The fall in the dispersion will be great enough to ensure that despite the increase in the mean, there is some age, above which the high-lifespan tail of the new distribution will fall below the high-lifespan tail of the old distribution. (Both distributions are to be given in terms of proportions of the populations to which they apply, so as to avoid issues about the effects of a higher mean on the size of the population.)

C. The mean of the distribution of years of ill health or disability at the end of life, and the overall shape and the dispersion of that distribution, will remain unchanged. Note that this effect is given in terms of years, not in terms of proportion of life. So the number of years of ill health or disability remains the same, even if lifespan increases.

D. Any correlation between position in the distribution of lifespans, and position in the distribution of years of ill health or disability, remains unchanged.

Thus, average prospects will improve: longer life, with no more years of ill health or disability at the end of life. But there is a tail of the distribution of lifespans, in which prospects are made worse by the change.

Now we come to the questions.

1. Should you take this action, if it is to apply to all people already born or currently in the womb, but not to anyone else?

2. Should you take this action, if it is to apply to all people who have not yet been conceived, but not to anyone else?

3. Should you take this action, if it is to apply to all people already born, currently in the womb, or not yet conceived?

Two points should be noted, before we consider answers.

The first point is that you are confronted with a single choice: take the action, in accordance with the terms of whichever one of 1., 2., and 3. is in force, or do not take the action at all. You are told which of the three is in force. You do not get to choose which one is in force.

The second point is that in drawing a line at conception, I do not mean to take a stance on whether embryos are people. I simply want to recognize the difference between entities that already have a determined genetic endowment, and potential entities that do not. The significance of genetic endowment, is that it is likely to have quite a lot to do with prospects for lifespan and for infirmity in old age.

The case against taking action in 1. looks quite strong. Given that genetic endowment and lifestyle to date have a substantial influence on lifespan, there would be some group of people, ones with good genetic endowments and healthy lifestyles, who constituted a modest proportion of the population, such that we were aware of the criteria for membership of that group, and such that we could say that taking the action would shift the odds against members of that group, to an extent that one would not regard as trivial. Kantian objections to the use of people as means to other people's ends come to mind. The other people in question would be the people outside the group.

The fact that the members of the group would be people who were already well off, in that they would be people at the high end of the distribution of lifespans, hardly seems to be a satisfactory response. Imposing reductions in lifespans seems to be rather more fundamental than imposing high tax rates on high incomes.

My initial feeling is that the obvious utilitarian case for taking action in 1. is outweighed by considerations such as these.

One objection to this view, would be that a decision not to take the action would itself be a decision to act: that is, that refraining from action would not be abstention, but a positive choice for the other side, and that one would be just as responsible for that as one would be for a choice to take the action, and responsible in the same way. Then a choice not to act would amount to deliberately disadvantaging those who were not in the group with long life expectancies. I shall not explore this view here, but it is a view that could be argued.

The case against taking action in 2. looks much weaker. People as yet unconceived have neither any particular genetic endowment, nor any particular lifestyle. It is tempting to say that there would be, in the future population, some members of a specifiable group of people (the group of people with good genes and healthy lifestyles), who would be worse off than they would have been, had the action not been taken. But that objection would not be rightly phrased. The word "they" would have no referent. The complaint that some members of a specifiable group would be worse off, once re-phrased to remove this difficulty, can amount to no more than a complaint that the distribution of lifespans, for the whole population, would be different. Given that, the utilitarian case seems to be a good one. In 2., a choice to take the action would be the right choice.

It might seem that the word "they" would have a referent, at least in the next few generations, if there was a strong hereditary element to longevity. It could refer to the descendants of people who were currently alive and who had good genes. But I doubt that this would be enough to create a referent. Since we are concerned with people not yet conceived, there would only be potential descendants. Any particular person currently alive and with good genes might not have any descendants, even though it would be very probable that some people or other, drawn from the set of those currently alive and with good genes, would have descendants.

There is a parallel with John Rawls's veil of ignorance. It is a veil of total ignorance. The people behind it have no particular characteristics, until they are dropped into the society that they have designed. So they can only sensibly think about overall distributions. There is a sense in which they cannot take up arms on behalf of a particular group on the basis that some arrangement would do an injustice to its members, even though criteria for membership of the group may be perfectly clear, because no-one has, at the time of design, characteristics that would determine whether he or she was a member. "Its members" lacks a referent. To make the parallel closer, we can imagine Rawls's deliberators thinking about possible changes to distributions that already apply in an actual society, a society which all the designers will join as a complete replacement population, in roles and with characteristics that will be allocated at random, once all existing members of the society have died.

I shall not reach any conclusion on the third possibility, applying the change to current and future people. The key question is this. If the future population will be, in total over the centuries, very much larger than the current population, can the utilitarian case for action outweigh the case against action that was set out in relation to 1.?

There is one more complication. Is it in the interests of a person to have descendants who enjoy long lives? If it is, then that would influence one's thoughts in relation to 3. Currently living people with good genes might lose some of their own lifespans. But suppose that the beneficial influence of good genes on lifespan was not passed down the generations to any significant extent, so that, for example, the great-grandchild of someone with genes that substantially improved prospects had no better chance than the average in the population of having genes that conferred such good prospects. Then the good genes of the current generation would not tend to keep a significant proportion of their descendants in the group that would potentially lose from the action. Then the members of the current generation with good genes might have self-regarding reason to favour the action.