 A fourth area of intimate mutual involvement concerns unity among the faculties of sensation themselves. For one thing, Herder implies that our underlying animal nature involves a sort of primordial fusion of perceptual with affective sensations (albeit that, unlike other animals, we also have a distinctive ability to suspend this fusion, an ability that he calls Besonnenheit). For another thing, he argues that the several faculties of perceptual sensation themselves form a sort of unity. His grounds for these two positions are again mainly empirical in character. In particular, he says that the unity of the several faculties of perceptual sensation is shown by clues that emerge in unusual situations and in pathological cases. For example, he argues that the dependence of the mature sense of sight on the sense of touch is shown both by the way in which the sense of sight develops in young children and by the way in which it develops after medical operations on previously blind people such as Cheselden’s blind man.