This paper discusses the notion that presence may be considered as a selection mechanism that organizes the stream of sensory data into an environmental gestalt or perceptual hypothesis about current environment. A par ticular environmental gestalt results in scan-sensing of the world in a particular pattern reminiscent of saccades and fixations in eye scan paths. The environment hypothesis is continually reverified or else a break in presence oc curs. Presence is therefore compared to visual hypothe sis selection in the work of Richard Gregory and Law rence Stark. The implications for measurement are discussed, and it is concluded that physiological measures indicating breaks in presence are worthy of study, and that the study of presence is also the study of what maintains an environmental gestalt.