Parity, Imprecise Comparability and the Repugnant Conclusion

Abstract

This article explores the main similarities and differences between Derek Parfit's notion of imprecise comparability and a related notion I have proposed of parity. I argue that the main difference between imprecise comparability and parity can be understood by reference to 'the standard view'. The standard view claims that 1) differences between cardinally ranked items can always be measured by a scale of units of the relevant value, and 2) all rankings proceed in terms of the trichotomy of 'better than', 'worse than', and 'equally good'. Imprecise comparability, which can be understood in terms of the more familiar notions of cardinality and incommensurability, rejects only the first claim while parity rejects both claims of the standard view.I then argue that insofar as those attracted to imprecise comparability assume that all rankings are trichotomous, as Parfit appears to, the view should be rejected. This is because imprecise equality is not a form of equality but is a sui generis 'fourth' basic way in which items can be ranked. We should, I argue, understand imprecise equality as parity, and imprecise comparability as entailing 'tetrachotomy' -that if two items are comparable, one must better than, worse than, equal to, or on a par with the other. Thus those attracted to the idea that cardinality can be imprecise should abandon trichotomy and accept parity and tetrachotomy instead.Finally, I illustrate the difference between Parfit's trichotomous notion of imprecise comparability and parity by examining how each notion might be employed in different solutions to the problem posed by the Repugnant Conclusion in population ethics. I suggest that parity provides the arguably more ecumenical solution to the problem.

Spectrum Arguments, Parity and Persistency

“…The possibility of parity has been defended primarily by Chang in a series of papers (see Chang, 1997Chang, , 2002Chang, , 2005Chang, , 2016aChang, , 2016b. When defending parity, Chang contrasts it with what she calls the trichotomy thesis, which says: "if two items A and B are evaluatively comparable, then A must be better or worse than B, or A and B must be equally good" (Chang, 2002, p. 660).…”

“…Both Chang and Qizilbash have argued that parity can help one block Spectrum Arguments and avoid their implications. In commenting on Parfit's proposed solution to how to avoid the Repugnant Conclusion (i.e., to invoke "imprecise equality"; Parfit, 2016), Chang (2016a) suggests that a better solution might be to accept parity. In writing about one of the arguments that give additional support to the Spectrum Argument in population ethics (the Mere Addition Paradox), Qizilbash (2007) argues that parity can help one block the Spectrum Arguments and thus avoid their problematic implications.…”

“…This article examines the proposal that parity can help one refute Spectrum Arguments, shows that this only works if one interprets parity in a specific way, and identifies some consequences of that discovery for the general debate on Spectrum Arguments, value theory and comparability problems. Both Qizilbash (2007Qizilbash ( , 2018 and Chang (2016a) have recently argued that one can dismiss the problematic consequences of Spectrum Arguments by accepting parity. I argue that their proposed solution to Spectrum Arguments is seemingly inconsistent with the standard definition of parity and suggest that those who defend the possibility of parity must specify what they mean by parity if they wish to block Spectrum Arguments.…”

The Good, the Bad, and the Transitivity of Better Than*

“…One response to the spectrum arguments appeals to incommensurability . Some philosophers claim that some of the elements in each spectrum are incommensurate in value with their predecessors, in the sense that they are neither better than, nor worse than, nor exactly as good as their predecessors (Parfit ; Handfield ; Chang ). These experiences, therefore, do not give rise to a betterness cycle.…”

Hard Choices

“…For another, we can have ‘imprecise’ cardinality among incommensurable items. Although there is no unit that measures the value of two items, perhaps there are fuzzy units or an indeterminate range of precise units by which the value of items can be measured, what Derek Parfit calls ‘imprecise comparability’ (Parfit 2016; see also Hsieh 2005; Sinnott-Armstrong 1988: 66–67; Hurka 1993: 87; for a discussion of Parfit's imprecise comparability, see Chang 2016b). Since it is compatible with alternatives being incommensurable that one of them is better than the other with respect to V, the choice between incommensurables could be easy: choose the better alternative.…”