In the illusion case, the erroneous perceptual judgment is explained by appeal to sense-data rather than a directly experienced environmental feature

The distinction between sensory perception and judgmental acumen enables Austin to distinguish between central cases of illusion and central cases of delusion, and also to sketch explanations of what is going on in those cases that do not make appeal to sense-data. Austin takes the defender of (i) and (ii) to argue as follows. First, consider an illusion, for example a stick that looks bent but really isn’t. Such an illusion has two key features. First, it clearly involves a distinctive sensory