Sensitivity hasn't got a Heterogeneity Problem - a Reply to Melchior.

In a recent paper, Melchior pursues a novel argumentative strategy against the sensitivity condition. His claim is that sensitivity suffers from a 'heterogeneity problem:' although some higher-order beliefs are knowable, other, very similar, higher-order beliefs are insensitive and so not knowable. Similarly, the conclusions of some bootstrapping arguments are insensitive, but others are not (and since one motivation for endorsing the sensitivity condition was to provide an explanation of what goes wrong in bootstrapping arguments, this motivation is undermined). In reply, I show that sensitivity does not treat different higher-order beliefs differently in the way that Melchior states and that while genuine bootstrapping arguments have insensitive conclusions, the cases that Melchior describes as sensitive 'bootstrapping' arguments don't deserve the name, since they are a perfectly good way of getting to know their conclusions. In sum, sensitivity doesn't have a heterogeneity problem.