Perceptual constancy, often defined as the perception of stable features under changing conditions, goes hand in hand with variation in how things look. A white wall in the orange afternoon sun still looks white, though its whiteness looks different compared with the same wall in the noon sun. Historically, this variation has often been explained in terms of our experience of “merely sensory” or subjective properties – an approach at odds with the fact that the variation does track objective features (...) of the perceptual situation, such as illumination. One approach, becoming more common, is to account for the variation in terms of further “dimensions” to perceptual experience. Especially in colour perception, this is a natural thought to have but the idea is often left vague. In this paper I argue that the “dimensional” strategy has problems of its own, but is useful in drawing out some interesting complications in the way perceptual experience is structured. Specifically, the structure of “constancy spaces” brings out the different ways in which there is stability and instability in the experience of constancy, without the need for novel or merely subjective features. Instability arises in a contingent structural feature of perceptual experience. (shrink)