The enactive approach also has strong affinities with the sense-data tradition. According to Noë, an object’s visually apparent shape is the shape of the 2D patch that would occlude the object on a plane perpendicular to the line of sight, i.e., the shape of the patch projected by the object on the frontal plane in accordance with the laws of linear perspective. Noë calls this the object’s “perspectival shape” (P-shape). An object’s visually apparent size, in turn, is the size of the patch projected by the object on the frontal plane. Noë calls this the object’s “perspectival size” (P-size). Appearances are “perceptually basic” (Noë 2004: 81) because in order to see an object’s actual spatial properties it is necessary both to see its 2D P-properties and to understand how they would vary (undergo transformation) with changes in one’s point of view. This conception of what it is to perceive objects as voluminous space-occupiers is closely to akin to views defended by Russell (1918), Broad (1923), and Price (1950). It also worth mentioning that the enactive approach has strong affinities to views in the phenomenological tradition that are beyond the scope of this entry (but for discussion, see Thompson 2005; Hickerson 2007; and the entry on phenomenology).