 Like David Lewis and Frank Jackson, he endorses the view that our ordinary color concepts are captured in those that those with mastery of the concept possess. Johnston says that the ordinary concept of color is a “cluster concept”, which incorporates a wide set of beliefs. There are, he points out, many beliefs about color to which we are susceptible, beliefs resulting from our visual experience and our tendency to take that visual experience in certain ways. Johnston says that some of these beliefs are “core” beliefs, which we can contrast with the more “peripheral” beliefs. The point about the core beliefs is this: were such beliefs to turn out not to be true, we would then have trouble saying what they were false of, i.e., we would be deprived of a subject matter, rather than having our views changed about a given subject matter. By contrast, the peripheral beliefs are such that “as they change we are simply changing our mind about a stable subject matter” (Johnston 1992 [1997: 137]).