 Other voices within the groups maintained, in line with Husserl, that thinking and intuition can fuse together. This idea is advocated by Schapp (1910), Hofmann (1913) and Leyendecker (1913), who apply it to the phenomenology of perception, and by Heinrich, who presupposes it in his work on concepts (1910). For instance, Schapp holds that, in perception, intuitive contents and ideas (or concepts) can only be separated conceptually, but not factually: without ideas, we cannot perceive things (1910: 133f). Although Hofmann was critical towards the existence of sensations (the first chapter of his 1913 essay is a critique of this notion), he nonetheless puts Husserl’s concept of apprehension at the core of perception (as does Ingarden, see his 1997: 15ff): in apprehension, a subject “interprets” an intuitive content by means of a conceptual content (but see Mulligan 1995 for a different interpretation). According to Hofmann, perception is apprehension, even though the apprehended contents are not mere sensations, but structured “sight or visual things” (Sehdinge, see Hofmann 1913: 82; on the notion of Sehding, see Casati 1994). Furthermore, Leyendecker investigated the phenomenon of cognitive penetrability and various ways in which perception is permeable to thinking by discussing a large number of perceptual situations including various kinds of illusions, selective perception, the experience of “overlooking” something, etc.