The article presents an examination of the ostensibly basic human need for open space and exposure to elemental nature. Though often used to describe similar attributes of an environment, space and landscape are not quite equivalent. Space clearly is conceptually abstract, while landscape, though it involves environmental features distributed in space, is both more specific and more variable. The one constitutes a perception in which the mental contribution is the primary variable; the other constitutes a visual sensation in which the mental imagery is a fairly close duplicate of what in fact exists. The two key attributes of spatial adequacy appear to be isolation and difference. The determinants of spatial adequacy, both in its isolation and difference dimensions, lie in part in the nature of the space and in part in the individual and the constraints on his activities. Given the occurrence of change in personal values and demands for space and landscape, and change also in the availability of space and landscape for the satisfaction of existing values and demands, an adaptive mechanism would seem to be necessary whereby, at least in western societies, increasingly affluent and concerned populations will be able to accommodate to continued reductions in controllable space or landscape.