Sellars’s treatment of the sensory is particularly complex; this article can only summarize.  The context is, again, the idea that our concepts of sensory states are, in some important ways, like theoretical concepts.  Concepts of sensory states, however, are introduced to explain different phenomena from those that concepts of intentional states are introduced to explain.  They are originally introduced to explain illusions, hallucinations and such, cases in which people sincerely report and behave as if perceiving something that is not there.  Once introduced for those purposes, however, such concepts must be applied generally: we cannot think that we have sensations only in cases of illusion and hallucination.  A philosophically satisfactory theory of the sensory must account for the complexity and peculiarities of the language of sensory experience, both illusory and veridical.