Our ability to perceive our environment veridically and the stability of perception are noted. These occur in spite of the continuously varying stimulation impinging upon our senses, and are ascribed to what is labeled perceptual constancy. Two very contrasting theoretical approaches to explaining constancy have been put forth. The constructivist approach explains veridical perception by means of an inference-like process where an ‘intelligent’ perceptual system utilizes high-level mental processes in order to supplement the variable and/or insufficient sensory stimulation. The direct approach, on the other hand, maintains that the sensory information picked up by our perceptual system suffices to enable veridical perception and there is no need for positing the involvement of higher mental processes. The two theoretical approaches are described in some detail with Rock's The Logic of Perception (1983) serving as the model of a constructivist approach, and Gibson's The Ecological Approach to Visual Perception (1979) as the central exposition of the direct approach. The final section consists of a brief account of an attempt to reconcile the two theoretical approaches based on recent research pointing to the existence of two parallel visual systems.