 At the heart of Cohen’s account is a certain argument, which he calls his “Master Argument”. This argument depends on pointing out the extent to which the colors things look to have, vary with different viewing conditions, different classes of perceivers, and different types of animals. In short, it is built upon the premise that there is a vast range of situations in which there are variations in the way something looks, either to the same subject under different viewing conditions, or to different subjects under the same conditions.