Valtteri Arstila

There exist two widely used notions concerning the structure of phenomenal color space. The first is the notion of unique/binary hue structure, which maintains that there are four unique hues from which all other hues are composed. The second notion is the similarity structure of hues, which describes the interrelations between the hues and hence does not divide hues into two types as the first notion does. Philosophers have considered the existence of the unique/binary hue structure to be empirically and phenomenally well-grounded, and the structure has been considered to be primary because this can account for the similarity structure. Consequently, the unique/binary hue structure has played a central role in color philosophy. This calls for the assessment of the justification for its existence carried out in this paper. It is concluded that, despite the prevalent view among philosophers, none of their reasons for endorsing the existence of the unique/binary hue structure are justified. Since the notion of the unique/binary hue structure appears intuitively plausible for many, however, a sketch explaining this intuition is outlined at the end.

The question of the constituting nature of colour is largely open. The old dispute between colour objectivism and colour subjectivism is still relevant. The former has defended itself against accusations of not being able to explain colour structures, while the latter view has received criticism for not being able to provide a plausible theory of the location of colours. By weakening the notion of physical categories, making some of them perceiver-depended, colour objectivists have managed to overcome at least some of the previous accusations. However, the arguments based on Crane’s and Piantanida’s findings of the existence of binary colours like greenish-red and yellowish-blue, indicate the inadequacy of colour objectivism. Consequently, we have colours but our theories of them are false.

The philosophical debate over the nature of color has been governed by what we have learnt from color vision science and what color phenomenology suggests to us. It is usually thought that color eliminativism, which maintains that physical objects do not have any properties that can be identified with colors, can account for the former but not the latter. After all, what could be more obvious than the external world to be colored? Here I outline one color eliminativistic response to the objections based on phenomenology.