Incommensurability, Incomparability, and Robotic Choices.

Some comparisons yield puzzling results. In the puzzling cases, neither item is determinately better than the other, but they are not exactly equal either, as improving one of them just slightly still does not make it determinately better than the other. What does this kind of incommensurability or incomparability mean for robots? We discuss especially Ruth Chang's views, arguing for four claims. First, we defend her view that despite appearances to the contrary, formal incomparability does not follow - comparison of "apples" and "oranges" is not impossible. Second, rational value-assessment turns out to be very complicated in virtue of the non-linear relations between descriptive and evaluative features. These complications pose considerable challenges to robots, whatever views about incommensurability are adopted. Ruth Chang's theory introduces a fourth value relation "being on a par", and we argue, thirdly, that (unlike its rivals) it will pose a considerable extra challenge for robots, as it is a non-transitive relation (unlike equality or betterness). Fourthly, we argue that exercise of normative powers - Chang's suggestion for hard choices in contexts of parity - is not available in the case of (fully autonomous) robots.