Chapter six space perception and binocular vision. Realism = a philosophical position arguing that there is a real world to sense. Positivism = philosophical position arguing that all we really have to go on is the evidence of sense, so the world might be nothing more than an elaborate hallucination. Euclidean = refers to the geometry of world. We reconstruct the world from 2 non-euclidean inputs: the 2 distinct retinal images which are always different cuz the retinas are in slightly diff places. Vertically is 60 degrees up from center of gaze and. Binocular summation combination of signals from each eye in ways that make performance on many tasks better w/both eyes than one eye alone, this might be reason y our eyes moved infront. Binocular disparity = differences b/w 2 retinal images of the same scene. stereopsis = ability to use binocular disparity as a cue to depth.