Space and perceptual boundaries

In consideration of the spatial structures of sensory experiences, an ‘Externality Thesis’ is commonly proposed, according to which awareness of sensory boundaries is also an awareness of the presence of a space beyond these boundaries. The paper evaluates the Externality Thesis in the context of vision and touch. More specifically, relying on mereotopological theories, it is shown that the notion of spatial boundaries is ambiguous as it encompasses various distinct ways in which entities may be connected by a boundary. It is argued that only some of these ways are able to support the Externality Thesis. In particular, it is claimed that while bodily boundaries of which one is aware in tactile sensations are such that the awareness of them provides support for the Externality Thesis, the analogous claim is not true about the boundaries of the visual field.