 Finally, another difficulty with dispositionalism, as it is standardly expressed, is the one that Hardin (1988/1993, 2004) has stressed. As our knowledge of color vision has grown, it has become increasingly more difficult to specify normal observers, and standard viewing conditions in any but an arbitrary way, arbitrary from the point of view of metaphysics. To be sure, there are conventional reasons for picking out some observers and some viewing conditions as special, but we can, without too much trouble, imagine these changing. And with respect to normal observers, we have found that in fact, as things stand, there is a wide range of variation among competent color perceivers. As we shall see in the following section, these considerations have led Cohen to modify the standard dispositionalist account in favor of a “more ecumenical” color relationalist theory, one that relativizes the dispositions to groups of perceivers, and types of viewing conditions.