 These considerations are not trivial, for when we examine the examples that Lewis and Jackson give of the relevant constraints on color, we find that they function as items of knowledge, rather than as mere beliefs. Indeed Lewis often refers to the folk beliefs as items of “common knowledge” (Lewis 1997). In Jackson’s case, consider what he says, concerning what he calls “the prime intuition about colour” (1998: 88): “red” denotes the property of an object putatively presented in visual experience when that object looks red. This he also calls “a subject-determining platitude for ‘red’” (1998:89). What is particularly interesting is what Jackson does with this “prime intuition”. He says that it seems trivial, but its significance is that it tells us