Prioritarianism and the Measure of Utility

Abstract

HERE I present a challenge to prioritarianism, which is, in Derek Parfit's words, the view that ‘we have stronger reasons to benefit people the worse off these people are’.1 We have such reasons, according to this view, simply by virtue of the fact that a person's ‘utility has diminishing marginal moral importance’2 —i.e., that equal improvements in a person's well-being matter less, morally speaking, the better off she is in absolute terms. It follows, from this view, that one might have stronger reason to benefit someone who is less well off rather than someone who is better off, even when this benefit would amount to a lesser increase in utility than a benefit to the better off person.3 In discussions of prioritarianism, it is often left unspecified what constitutes a greater, lesser, or equal improvement in a person's utility. In his own defence of prioritarianism, for example, Parfit explicitly prescinds from ‘difficult questions … about what it would be for some benefits to be greater than others’ and ‘simply assume[s] that we can distinguish between the size of different possible benefits’.4 Parfit just stipulates numerical benefits of different magnitudes that comprise intervals along a whole number cardinal scale that is meant to represent the absolute levels of people's utility in linear fashion.5 We are supposed to assume that this scale provides an accurate representation of people's utility. But we are not offered an account of what constitutes the measure of the size of the units on this scale. I shall argue that prioritarianism cannot be assessed in such abstraction from an account of the measure of utility. Rather, the soundness of this view crucially depends on what counts as a greater, lesser, or equal increase in a person's utility. In particular, prioritarianism cannot accommodate a normatively compelling measure of utility that is captured by the axioms of John von Neumann and Oskar Morgenstern's expected utility theory. Nor can it accommodate a plausible and elegant generalization of this theory that has been offered in response to challenges to von Neumann and Morgenstern. This is, I think, a theoretically interesting and unexpected source of difficulty for prioritarianism, which I shall explore in the remainder of this article. In presenting this challenge, it will be useful for me to begin with a case that is closely modelled on one that Thomas Nagel presents in his essay ‘Equality’6 —and with which Derek Parfit opens his Lindley Lecture ‘Equality or Priority?’7 Imagine that you are the parent of thirteen-year-old twins. For the sake of interpersonal comparability, let us assume that they are identical twins with identical preferences. They differ, however, in the following crucial respect: one of them has recently been diagnosed with a condition that will soon give rise to a severe mobility-impairing disability, but the other has been given a clean bill of health. You need to change jobs and must therefore choose whether to move your family to cramped urban accommodations in an unpleasant and dangerous neighbourhood or to the and of a would be as your own well-being is But they would not be as the well-being of of your is you move to the your who and will be in and but your will have to that will but from the of his you move to the your will but your will not this marginal benefit to the of a move to the I shall be greater than the marginal benefit to the of a move to the It that a would for the Nagel would that you have reason to move to the Parfit would that you have reason to move to the but would that this reason is rather than In other words, Parfit would that you to move to the simply on account of the fact that improvements in well-being matter the worse off someone is in absolute terms. of such to the worse off is Parfit an the is as well off someone is in to someone to be a matter of moral that on the view, is well off people are in absolute the worse off they the well-being It not and well off they are in to In of this view, Parfit that would be just as to benefit the even who better the following of case a case in which you have a this thirteen-year-old has recently a that is a that will soon the severe and a that will that you must for the in the or the it is whether your will the the marginal benefit to your of a move to the in would be greater than the marginal benefit to of a move to the the and to the view just as a reason to move to the in this case as one has in the this prioritarianism for a of of expected the in is utility. It for the of the of the of possible that might be the of this the the of such is by the that it will utility of given is the of utility in that person's utility has been the but marginal moral in the of by simply by this by the that this will such a expected the of a reason to move to the rather than the will be just as in the case as it is in the In of the Derek Parfit a and to than the one just the that Parfit a the expected of the in just the a But in to in such Parfit that the to the of are simply expected the on Parfit's to these well as to the a person's expected the greater the moral of a marginal increase of a given size to his expected In other words, not are the levels of a person's utility that are the different possible of a morally in a that the but is a person's expected of utility that is with a given in a person's expected utility and his utility and to it a with with a with I shall this Parfit's of Parfit this view by just as such as are to about the of people's of as well as the of the they can and have for people's for utility as well as for of utility prioritarianism less reason to move to the in the case as with the the will that the parent to move to the in the and it would be to move to the prioritarianism therefore the what one to move to the the of prioritarianism that to to of prioritarianism, the I shall in this is simply in along the of the other than between the possible of a you are simply to this person's expected rather than to to prioritarianism in or it is therefore to for the in the following is a of defence of this one as I that are one that will the measure of a person's such will to axioms of expected utility theory. It that you will this with an other than that which it is in his to you to his expected utility. fact provides you with reason to his expected utility rather than to this reason is not by reason that you or for example, or that in of to other than what is in this In this are that might from the of a It is for the to the in from of to you not have you are to your expected utility in this case on that this is what it would be for to is the of prioritarianism in or In this I have to a case a parent and a a case is useful it that the of the parent to this a for the of this will in to They a of the to the and other of this one in from the and of They therefore us with a case of prioritarianism than one in which an is by and is, however, an of the that it for these parent is the of his the of a is someone who is to the of a parent has a reason to that This reason will to to other of who are whether they benefits to they are not even I to the that the parent the expected utility of his one this might from his and to a of prioritarianism as on of to with case that better would be one that that to the to a rise to reasons to on of the of a that are to or other such as that of an who is to let us in the to that who must the the move to the or the are the rather than his This in the to you as your or and is to You are however, his parent is the it that parent is an of a of which you are a but someone to you have of or the parent is a you not of the the parent is has and you must whether to the parent to in a or in a as the of the parent and of the are for of these are it is for you to just on the in which this on the of your one and In this I would argue even the view that you you are to the parent in a that the expected utility of the I shall argue in you are to on that this is what it is for to I argue that you are to on that this is what it is for your to I will not your to in what to with different of reasons from to with preferences. 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of an is would In for the utility to a measure of we will need to the of the to that are rather than or in It will be to these a person's might be by or by of even they to to the von In to the measure of will need to be along the of that the would have with this I shall assume that the that give rise to a person's utility are in and in along the just I therefore from the of that the that as the of expected utility theory are in and by what people would I John who that the and of as which that in this need not be to a representation of a person's preferences. can be a utility it the a would have she and are and in this it is not by virtue of the of that the these provides a measure of the utility to which Rather, we can the following in of the that the utility provides a measure of the person's utility that is of to prioritarianism, which is to well-being or she and she would of the one that is better for a that the she would have she and … we for the sake of that the von axioms are the of prioritarianism the following Parfit that prioritarianism would be in with the it be to that we to people in in which they not choose to be Parfit however, that the is not to choose that the his expected utility by to the Rather, according to the choose that his in a by to the his for such a are that is a one in that would be better for and this would be better for is that Parfit to that other than what is for the in from well would in with In other words, to the or of such a given that the move to the is of expected utility than a move to the we can from expected utility theory that it is in the to choose a move to the the it is in the to choose and what would his expected utility cannot in the that Parfit This is expected utility theory the magnitudes of a person's expected from it would be in the to choose a move to the the on Parfit's that is a one in that would be better for and this would be better for is it that such a move to the would his expected us to the of the the that the own utility is identical to This is and provides a of the view, for the following case for than the on one is cannot on in between the and the of the can it on other in that utility This is prioritarianism is the view own utility as with the utility of one to moral to the utility of the less well off they are in absolute terms. therefore even on the that utility are this not would it be in the to a move to the the for but it would be for his to a move to the the for she in his it would be for the to that his that on his and it would be for his to that that on she in his and in of these are they a of the benefits of the the in In of it is to it be as a would rather than for the to choose the the for for prioritarianism to which I have been have the that the von axioms are of It is, I a matter of whether or not of the axioms are such I would that the is such a In other words, for given of it not to be that an one to the other or be between the of that are not is the for a person's need not be axioms of and have stronger than the of to be of in the case of these however, have been such for the of of prioritarianism, I for reasons I shall in the to assume the soundness of the axioms of and diminishing marginal moral of utility that is as a of the of are as on a cardinal scale. a representation is, a that than is by the however, be to that the view would be these that are in to the It for example, be to that prioritarianism would not such as that accurate and cardinal of levels of utility on a linear scale. therefore to the of the for the sake of the soundness of his that utility can be in such however, one this that the of are in such as on a cardinal for the of the and of would be a cardinal representation is, for example, with the of to which people in to the of even the of can be as a number on a cardinal one will be with will be such that one will one to and the is a on this cardinal scale than the however, this is the such not to be of the cardinal scale of utility would for the soundness of the however, be on This is reasons to this are not by the that utility can be in cardinal given on the of the of the is than the other axioms to the between prioritarianism and in that in of the of expected utility in such that this the his might a challenge to the that the is a of that are in the In other words, for increase in a given of the of a one will have the for such an increase or the For example, an increase of in of a will be to the whether the increase is from a of to a of that from a of a to a or from a of a to a of that of that are linear in the has been by who a of from the as response to that an of which to be such as have offered of the as a of I view that this is a of however, one with the of and the of that to be linear in the it not that one must expected utility theory is the of a which the of expected utility theory that to the von in been or of expected utility theory that or in a that the that from of these from this have been as with a generalization of von Neumann and Morgenstern's theory that has to be as expected utility this theory the of in the it with the expected utility theory of von Neumann and the following crucial the of utility is a of It is this that has been the of in this for the of from what prioritarianism in the case of prioritarianism will one the axioms of von Neumann and with the axioms of the generalization of theory. can a along to in which the of a move to the it would be in the for someone who to these axioms to be with the of It will be for the reason as that prioritarianism for a of the moral of magnitudes have been by In some such a will a for a to in a that is to what it would be in the for the to I have however, that it is for a to choose in with such I the of this Parfit in his defence of prioritarianism, from ‘difficult questions … about what it would be for some benefits to be greater than I to have that such questions cannot be Rather, the soundness of the view on It is a of this view for the reasons I have just in this it cannot accommodate one of the and of and expected utility In to the of to between the possible of a of the that has been the of this Parfit must a normatively compelling von measure of utility along with the expected utility theory that has been offered as an to the soundness of this must a different measure of utility which is not a of that to axioms of It is plausible to that such measure will of some in to the cardinal scale of utility that prioritarianism of has been by a number of as an to expected utility of a cardinal scale of utility the a cardinal scale of utility is from people's between of of in of that are by or the measure of utility is from of that are to about rather than the will not a between and the of prioritarianism in In however, the on the for given of in that condition are of marginal utility. This is and normatively It is plausible to assume that the marginal utility of will the for the which such utility an of expected utility theory the of in which one is not one will the in plausible not a clean to expected utility theory I have in the that von expected utility theory cannot the measure of well-being to which Parfit moral of Parfit might the soundness of this might on Parfit's that it from this that Parfit must the axioms of that theory. Rather, it is to Parfit to the view that the axioms are an accurate of of the of the that the measure of even when the in are to that are ‘utility of expected utility theory might simply a cardinal measure of the of the rather than a measure of Parfit can simply the von measure of well-being the of that the axioms are axioms of a of a person's well-being from what it would be in to is however, to this would be with the account of reasons, and the that and in to this account is the of the on which the of his In this of the to a person's Parfit that when ‘we some possible for in the we that this is the that this would have the reasons to to Parfit a between and In a are … when we give us reasons to are not … when we some that we have reasons not to and reasons, or reasons, to This of off the of the we Parfit's own to one reasons to a between and the measure of a person's of a such a that a person's and different that she might will be that is, they are that not other about the amount of some Rather, these the of which of a scale of of well-being This is is measure of the of different that to a person's I with that the fact of the that the measure of I not an of is to the case for a the to well-being of a of or the cardinal measure of or I think, be by preferences. for example, that the to well-being of a of the is the of to the cardinal measure of the of this It would be a to on a cardinal measure that in such as the number of that are of as might not give rise to that is as as even in the case of of the or of the as they the and of might be of greater or lesser on or well is This would be by the fact that it might be in to own to of such is to it is even we assume that these are in It would from the that is the that equal of are must be to Rather, of might have diminishing marginal to the absolute of well-being of the who We would to a between of and the of in to the of that the of has diminishing marginal the measure of the of are to the following that Parfit on of Parfit that prioritarianism from the fact that we have greater reason to that is off than we have to that person's she is an of the us to a case of someone by the on the of the that she has just … is by of and by the Parfit would that a moral would have reason to that person's rather than of an that the measure of utility however, have account the of from a given of one is well off or This is that from the of as well as the of a I in of of the of that it might be for a to from a of his is from that of his is it would be for the to will have account the of or is would to be for the to of the in the that is off even in would be of such provides for that it would be for the to expected utility by for the rather than the in with the of In that the is to expected utility rather than in I have been that the of for this of is in other than his to about his in the matter in other I have to one well the would in with I have is that the case for the to the the might be in other than the or of the or of it might be in might be as a of according to which the of utility is to the that this is what is from an of view rather than from the of the or of moral a would not be by the fact that the view a that is from the of view of the of the has a in the Rather, would that such a is on the of the that the would a better the to the in of the fact it would be from the of his own and for to such a what us about is not the but the by the It is the of the the need of the the of the and fact that they are worse off in the than is But it is not as an of is in that is greater, need and therefore for the the the and not for us give them It is when the is on a for and the of and other that the case for prioritarianism is when it an that from such of Parfit's and defence of prioritarianism is to that about that to in well be captured by a prioritarianism that is in moral view this of prioritarianism to which Parfit in his Lindley one not need to well off will or might be in to the of reason to benefit a given it not well off are in to of moral reason to someone a benefit can be simply from about his absolute of as well as in in the case of the in prioritarianism an to and other to in this prioritarianism, in or has been that it not a to that the moral of This is in to of the that has been the of this to in such a one be rather than to that in the that by give of to a worse off in other the of different such as the case with which I This provides for the that it is not simply on account of absolute expected or or a of the we benefits to the off than benefits to the well Rather, it is when and some or will or might worse off than that we must to benefits to We give to the worse off it that some are worse off than and not simply of absolute prioritarianism not