ABSTRACT
Virtual realities, however, appear to form a third, distinct category. With appropriate headsets, feedback from bodily movements and visual displays they may give the appearance of being virtual worlds extended in physical space, but they have no actual 3D physical extension. One may appear to move around such virtual worlds, but these apparent changes in self-location do not correspond to actual changes in location. Such virtual worlds are ‘physical’ in so far as their existence depends on the information provided by appropriate physical equipment, but unless this information is translated into an observer’s experience, no independent ‘virtual reality’ exists. In principle, virtual objects can be given what appear to be physical properties, for example, the observer may wear a gauntlet which is programmed to resist closing around a visually perceived, virtual object, making the latter feel ‘solid’. In truth, however, there is nothing solid there.
