Determinables appear to be causally unspecific, in having fewer powers—in being able to contribute to causing fewer effects, in the circumstances—than their associated determinates. For example, red has the power to get Sophie the pigeon, who pecks at any red thing, to peck; but red doesn’t have the power to get Sophie’s picky cousin Alice, who pecks only at scarlet patches, to peck—for a red patch might be not scarlet, but burgundy (see Yablo 1992, Wilson 1999, and Shoemaker 2001). Such a lack of causal specificity, combined with a principle of individuation of scientific properties according to which they are (perhaps only contingently) distinguished by different sets of powers, has been taken to support not just the existence but the irreducibility of determinable features.