This chapter reconsiders the notion of perceptual constancy from the ground up. It distinguishes the phenomenology of perceptual constancy and stability from a functional characterization of perception as aiming at full constancy. Drawing on this distinction, we can attend to the phenomenology of constancy itself, and ask to what extent human perceivers attain constancy, as usually defined. Within this phenomenology, I distinguish phenomenal presentations of spatial features and color properties from categorizations, conceptualizations, and judgments that underlie verbal or other responses (...) to those presentations. Although phenomenal presentation and categorization commonly co-occur, they are distinct aspects of experience. After reviewing several standard descriptions of constancy, I present laboratory findings and my own phenomenological descriptions by way of confirming that, although perception "tends toward" constancy, human perceivers do not usually attain full constancy for either spatial or chromatic properties (as many investigators acknowledge). For spatial perception, I find that the phenomenology has been systematically misdescribed, and I offer a more adequate description of the phenomenology of everyday spatial perception. However, my greatest quarrel with previous theory concerns the functional aim of the constancies. I argue not only that perception does not achieve full constancy but that we should not characterize it as aiming for full constancy. Rather, perception seeks a stability of representation suitable for guiding our actions and which can also, as needed, enable us to classify and re-identify objects by phenomenally presented properties such as shape, size, or color. Further, I argue that theorists should not confuse these classifications with the qualitative character of phenomenal experience. My arguments underscore the need to distinguish phenomenal representation (better, "presentation") from conceptual categorization, and to distinguish perceptual presentations from subsequent processes that are involved in responding to them. (shrink)