Abstract: Some of our judgments are unstable, in the sense that they are an artifact of, or endogenous to, what else we see. This is true of sensory perception: Whether an object counts as blue or purple depends on what other objects surround it. It is also true for ethical judgments: Whether conduct counts as unethical depends on what other conduct is on people’s viewscreens. There are plausible evolutionary explanations for these findings. As behavior in general regresses, actions that were previously seen as bad or as terrible may come to be seen as fine or mildly bad. Call this “opprobrium contraction.” As behavior in general improves, actions that were previously seen as fine or as mildly bad may come to seem bad or terrible. Call this “opprobrium expansion.” Because law has a signaling function, it can heighten or diminish these phenomena.