Frank Jackson formulated his knowledge argument as an argument for dualism. In this paper I show how the argument can be modified to also establish the irreducibility of the secondary qualities to the properties of physical theory, and ultimately “secondary quality eliminativism”–the view that the secondary qualities are physically uninstantiated. In addition to being of interest in its own right, this new argument provides a perspective to better see that certain popular would-be refutations of the knowledge argument do not work (against either version). But it also introduces some complications that will force us to take an unexpected detour through the pros and cons of naturalizing intentionality before (tentatively) embracing Jackson’s dualist conclusion.