 The phenomenon of dreams is used to highlight the difference between her notion of the sensible world and George Berkeley’s. He defines a sensible thing as nothing but a collection of sensations. Shepherd complains that this definition is incomplete because it excludes properties of continued and external existence. This is why Berkeley’s doctrine is both unconvincing and difficult to refute according to her diagnosis. Atherton (1996) argues that she misunderstands Berkeley’s Idealism. The occurrence of dreams is overlooked by Reid and others who maintain that extension, motion, and other primary qualities are not sensations, but real qualities existing externally and independently. The fact that extension and motion appear just the same in dreams as in sense experience shows that they are sensations in experience, too. Motion and extension are capable of causing sensations to which we give the same names, but the causes of sensations cannot be sensations according to Shepherd.