  Quine claims that the dispositions he relies on in his account of language are like the case of fragility rather than the case of Caesar. The disposition to assent to an observation sentence when receiving certain stimulations is a physical state of the person concerned; in particular, presumably, of his or her brain. The claim that a given person has such a disposition is thus a claim about the state of a physical object. It is, moreover, a claim that we can test, at least under favourable conditions. There is no reason to exclude it from regimented theory.