‘Incommensurability’ and Vagueness: Is the Vagueness View Defensible?

Abstract

The vagueness view holds that when evaluative comparisons are hard, there is indeterminacy about which comparative relation holds. It is sceptical about whether there are any incommensurate items (in some domain). The sceptical element of John Broome’s version of this view rests on a controversial principle. Robert Sugden advances a similar view which does not depend on this principle. Sugden’s argument fails as a vagueness view because it assumes rather than shows that there are no incommensurate items (in some domain). Nonetheless, I argue that an interpretation of his argument constitutes a defensible vagueness view which is supported by intuition about examples. On this interpretation Sugden’s view can be mapped onto Broome’s application of a supervaluationist view of vagueness. It is also (on this reading) a close relative of James Griffin’s ‘rough equality’ view when this is interpreted in terms of vagueness. On an alternative interpretation Sugden’s view is not sceptical about incommensurateness. On this interpretation he does not defend a vagueness view and is ‘sceptical’ about the contribution of the philosophical literature to our understanding of rational choice.