Will Davies

This paper resolves a paradox concerning colour constancy. On the one hand, our intuitive, pre-theoretical concept holds that colour constancy involves invariance in the perceived colours of surfaces under changes in illumination. On the other, there is a robust scientific consensus that colour constancy can persist in cerebral achromatopsia, a profound impairment in the ability to perceive colours. The first stage of the solution advocates pluralism about our colour constancy capacities. The second details the close relationship between colour constancy and contrast. The third argues that achromatopsics retain a basic type of colour constancy associated with invariants in contrast processing. The fourth suggests that one person-level, conscious upshot of such processing is the visual awareness of chromatic contrasts ‘at’ the edges of surfaces, implicating the ‘colour for form’ perceptual function. This primitive type of constancy sheds new light on our most basic perceptual capacities, which mark the lower borders of representational mind.

I argue that it is possible to perceptually represent colour relations between two objects, without perceptually representing their colours. Such primitive relational colour representation goes against the orthodox view that we represent colour relations by virtue of representing colours. I first argue that under certain assumptions, PRCR is conceptually and even nomically possible. I then compare two possible models of PRCR: the linguaform model and chromatic edge model, the latter involving iconic rather than discursive representation. I argue that the chromatic edge model gives a better account of putative cases of PRCR in cerebral achromatopsia, a rare disorder of colour consciousness.

This paper presents a new response to the colour similarity argument, an argument that many people take to pose the greatest threat to colour physicalism. The colour similarity argument assumes that if colour physicalism is true, then colour similarities should be scrutable under standard physical descriptions of surface reflectance properties such as their spectral reflectance curves. Given this assumption, our evident failure to find such similarities at the reducing level seemingly proves fatal to colour physicalism. I argue that we should dispense with this assumption, and thus endorse the inscrutability of colour similarity. This strategy is inspired by parallels between the colour similarity argument and the explanatory gap between mind and body made vivid by Jackson’s (1986) knowledge argument, and in particular by type-B physicalist responses to that argument. This inscrutability response is further motivated by cases in chemistry and biochemistry in which analogous scrutability theses fail to hold. Along the way, I present a challenge to standard formulations of the colour similarity argument based on the extreme context sensitivity of the similarity relation. Most presentations of the argument fail to control for such contextual variation, which raises the distinct possibility that the argument equivocates on the similarity relation across its premises. Although ultimately inconclusive, this context challenge forces a significant reformulation of the colour similarity argument, and highlights the need for much greater care in handling claims about colour similarity

The orthodox monadic determination thesis holds that we represent colour relations by virtue of representing colours. Against this orthodoxy, I argue that it is possible to represent colour relations without representing any colours. I present a model of iconic perceptual content that allows for such primitive relational colour representation, and provide four empirical arguments in its support. I close by surveying alternative views of the relationship between monadic and relational colour representation.

Colour vision plays a foundational explanatory role in the philosophy of colour, and serves as perennial quarry in the wider philosophy of perception. I present two contributions to our understanding of this notion. The first is to develop a constitutive approach to characterizing colour vision. This approach seeks to comprehend the nature of colour vision qua psychological kind, as contrasted with traditional experiential approaches, which prioritize descriptions of our ordinary visual experience of colour. The second contribution is to argue that colour vision does not constitutively involve the ability to see colours, in a natural and categorically committed sense. I argue that two subjects exactly alike in respect of their constitutive colour vision abilities could differ in respect of whether or not they have categorical perception of colour. The argument is supported by thought experiment and dissociations observed in cognitive neuropsychology. The argument also bears connections to recent neo-Whorfian accounts of colour categorization. _1._ Introduction _2._ Colour Vision, Experience, and Natures _3._ The Central Argument _3.1._ Colour constancy and discrimination _3.2._ Dissociating colour vision and categorical perception for colour _4._ Whorf and the View from Cognitive Neuropsychology _5._ Conclusion

Psychiatry uncomfortably spans biological and psychosocial perspectives on mental illness, an idea central to Engel's biopsychosocial paradigm. This paradigm was extremely ambitious, proposing new foundations for clinical practice as well as a non-reductive metaphysics for mental illness. Perhaps given this scope, the approach has failed to engender a clearly identifiable research programme. And yet the view remains influential. We reassess the relevance of the biopsychosocial paradigm for psychiatry, distinguishing a number of ways in which it could be (re)conceived.

Colour constancy is a foundational and yet puzzling phenomenon. Standard appearance invariantism is threatened by the psychophysical matching argument, which is taken to favour variantism. This argument, however, is inconclusive. The data at best support a pluralist view: colour constancy is sometimes variantist, sometimes invariantist. I add another potential explanation of these data, complex invariantism, which adopts an atypical six-dimensional model of colour appearance. Finally I prospect for a unifying conception of constancy among two neglected notions: discriminatory colour constancy and relational colour constancy. The former arguably marks a common core capacity that is present across widely differing viewing contexts.