 Another major objection to the physicalist (reductive) account concerns whether the properties can satisfy the principle of “Unity”, as described by Johnston,  (see section 2.2).  This principle points to the fact that the various colors, it would seem, are the kinds of properties that fit together in characteristic ways to form structured color arrays, with a distinctive 3-dimensional character, built on attributes such as hue/saturation/brightness (or hue, chroma, lightness). The principle of Unity would seem to pose a serious problem for the Color Physicalist (see Hardin 1988; Thompson 1995; Maund 1995, 2011). As McLaughlin concedes, the problem is 