  Beyond these points, however, there is, from a Quinean perspective, a limit to how detailed an account we should expect to have of the acquisition of sophisticated cognitive language. Mastery of an observation sentence corresponds (more or less) to a relatively straightforward disposition: to assent when receiving a stimulation pattern within a certain range. For most sentences, however, this is not the case. What disposition must one have acquired in order to count as understanding a sentence such as “The economy is in recession”? No doubt the disposition to assent in response to evidence is required, but what counts as evidence is almost unmanageably diffuse. In such a case, the links between sensory stimulation (such as that induced by the sight of words in a newspaper) and assent are “multifarious [and] not easily reconstructed even in conjecture” (1960, 11). A relatively clear-cut account, of the sort that Quine gives of observation sentences, is simply not available.