Originally published in 1981, this third volume deals with the empirical data base and the theories concerning visual perception - the set of mental responses to photic stimulation of the eyes. As the book develops, the plan was to present a general taxonomy of visual processes and phenomena. It was hoped that such a general perspective would help to bring some order to the extensive, but largely unorganized, research literature dealing with our immediate perceptual responses to visual stimuli at the time. The specific goal of this work was to provide a classification system that integrates and systematizes the data base of perceptual psychology into a comprehensive intellectual scheme by means of an eclectic, multi-level metatheory invoking several different kinds of explanation.