Perception drives discussion in philosophy and the cognitive sciences because it forms our most intimate sort of acquaintance with the world. This chapter introduces the traditional philosophical problem of perception concerning whether our naive sense of perceptual awareness survives arguments from illusion and hallucination. It discusses empirically motivated theoretical issues about perception. The mainstream of cognitive science understands perception as an information-processing problem. J.J. Gibson suggests that unconscious inferences are unnecessary for vision since information concerning features that matter to the creature is present in the pattern of light that reaches the eye, or the ambient optical array. D. Marr's innovation is the framework he proposes for understanding perception in computational terms. The chapter recognizes movement-involving or motor-based constraints in the solution of the information-processing problem. It explains the proper role of phenomenology, and the limits of appeals to phenomenology in theorizing about perception.