Abstract: Blocking the Continuum Argument for the Repugnant Conclusion by an appeal to incommensurabilities in value, as has been suggested by Parfit (2016), is an attractive option. But the relevant incommensurabilities (‘imprecise equalities′ in Parfit′s terminology) need to be very thoroughgoing to obtain this result: they need to be ‘persistent′ in the sense to be explained. While such persistency is highly atypical and might well seem to be problematic, I suggest how it can be accounted for if incommensurability is interpreted on the lines of the fitting-attitudes analysis of value relations. On this account, two items are incommensurable iff it is permissible to have divergent preferential attitudes towards them; for example, if it is permissible to prefer one to the other but also permissible to have the opposite preferece. It is easy to provide a modelling of this kind for persistent incommensurability. However, even if Parfit’s main suggestion can thus be defended, one of his substantive value assumptions – the Simple View regarding the marginal value of added lives – should be given up to avoid implausible implications.

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