 Central to those considerations are those organized by versions of what is known as the argument from illusion  ((6) above).[21]  The version of the argument that Austin criticizes can be reconstructed as follows. (i) There are cases of illusion in which we have a sensory experience as of seeing something of some sort with specific features but in which nothing has those specific features. This might be because, although we experience something of the sort in question, the thing we experience lacks the features in question; or it might be because we don’t experience a thing of the sort in question at all. (ii) In those cases, there must be something we experience that has the features in question. Call the things we experience in such cases sense-data. (iii) Since the cases in which we experience sense-data include cases in which no material things of the sort in question, or with the features in question, are experienced, it follows that sense-data are not (in general) material things, or elements in the environment independent of the individual experiencer. It follows that, in the cases in question, we experience things (or directly experience things) that are distinct from material things and we do not thereby experience (or directly experience) material things. (iv) Now it is a general principle about experiences that if we cannot discriminate the objects of two experiences on the basis of introspection, then those experiences must have objects of the same sort. Hence, if one experience has only sense-data as its objects, and not material things, and a second experience has as its objects something that we cannot discriminate on the basis of introspection from the objects of the first experience, then the second experience also has sense-data rather than material things as its objects. (v) Since every experience stands in the required relation to an experience with only sense-data as its objects, every experience has sense-data rather than material things as its objects. Hence, we never experience—or never directly experience—material things