In The Ecological Approach to Visual Perception James Gibson poses the following question:
The essence of an environment is that it surrounds an individual…the term surroundings is nevertheless vague, and this vagueness has encouraged confusion of thought. One such is the question of how the surroundings of a single animal can also be the surroundings of all animals. If it is assumed that no two observers can be at the same place at the same time, then no two observers ever have the same surroundings. Hence, the environment of each observer is “private,” that is unique.
So, how does Gibson resolve such a philosophical “puzzle”? He first notes that one can consider the layout of the surrounding surfaces in terms of a stationary point of observation, or one can consider the surrounding surfaces in terms of a moving point of observation. This latter consideration is much more useful because animals typically move about. So, for Gibson, “the available paths of locomotion in a medium constitute the set of all possible points of observation.”
Thus, all animals have an equal opportunity to explore the “persisting substantial layout” of the environment and in this way it “surrounds all observers in the same way that it surrounds a single observer.” By reconceptualizing visual perception in ecological terms, Gibson is able to cast off the ancient tradition of treating observers as standing “at the center of his or her private world.”
For Gibson, this fact of a moving point of observation is central to his approach to perception and its implications are “far-reaching”.