1. The aim of the talk. I argue that evidence from neuroscience and psychology concerning unconscious perception and phenomenal overflow reinforces the manifest image of the world. It does so by rendering the naïve realist conception of colour preferable over its reductionist competition.

2. The relocation story. The manifest image pictures colours as qualitative features of mind-independent objects. Because the qualitative nature of these features resists description in mathematical terms, post-Galilean science relocates them from the world to the mind, and hopes that they will eventually become explained in terms of their relation to consciousness. The resulting view construes qualitative features as mental qualities of sense impressions.

3. Rosenthal and unconscious perception. One problem with the relocation story is that it presupposes that sense impressions are invariably conscious (Rosenthal, 2016), whereas there is a lot of empirical evidence that they are not. For example, there is evidence that colours can be seen unconsciously (Moutoussis & Zeki, 2002; Norman et al., 2014). According to Rosenthal, there is no reason to assume that qualities such as colours are as we are aware of them when they are perceived unconsciously. If qualitative states can occur without being conscious, 'there is no reason to suppose that, when there is something it's like to be in a qualitative state, what it's like to be in it reveals all its qualitative character' (Rosenthal, 2005, p. 172). If so, it is also unjustified to think that colours elude mathematical treatment (Rosenthal, 2005, pp. 160–161). On Rosenthal's view, the hypothesis that colours can be perceived unconsciously (UPC) supports colour reductionism, thereby vindicating the scientific image of colour.

4. Naïve realism and unconscious perception. Just as Rosenthal, the naïve realist believes that attempts at explaining qualitative features such as colours in terms of their relation to consciousness are mistaken, albeit for different reasons. As Kalderon (Kalderon, 2007, pp. 594–598) points out, the relocation manoeuvre has resulted in the body-mind problem and the related hard problem of consciousness. The fact that these problems remain unresolved despite countless efforts suggests that relocation might have been a mistake. Perhaps colours are not properties of the mental after all. If so, locating them 'in the head' amounts to committing an 'introjective error'.

To some extent, Kalderon's diagnosis is supported by UPC. If qualities such as colours are consciousness-independent, an important reason to internalize them is lost. What is more, if perceptual experience of colour is transparent (cf. Weksler et al., 2019), it is unclear why consciousness should not reveal the qualitative character of colour. UPC is thus consistent with the naïve realist claim that colours are what they consciously appear to be, i.e. primitive mind-independent properties.

5. The argument for externalism about phenomenal character. But the reductionist will not be persuaded. They will be right to point out that consciousness-independence of colours does not entail that they are mind-independent. And since they endorse the representational theory of perception, presumably they will not be persuaded by any other standard motivation of naïve realism.

However, there is a different argument to be made for naïve realism. It trades on the fact that Rosenthal's view shares a crucial yet highly contentious assumption with the phenomenal overflow hypothesis. According to the latter, phenomenal consciousness 'overflows' access consciousness, i.e. one can be phenomenally conscious of something of which one is not access-conscious. Overflow entails that the neural basis of phenomenal consciousness is distinct from the neural basis of access consciousness (Block, 2005, 2011). Just as Rosenthal's view, overflow assumes that colours qua mental qualities are produced in visual cortex. Insofar as this assumption is implausible, the naïve realist conception of colour is preferable over Rosenthal's reductionist proposal.

More specifically, the argument for naïve realism goes as follows:

(1) the phenomenal overflow hypothesis is unmotivated and should be rejected (see e.g. Overgaard, 2018; Phillips, 2016);

(2) there is no phenomenal consciousness (PC) without access consciousness (AC) (from 1);

(3) the neural basis of PC is the same as the neural basis of AC (from 2);

(4) the neural basis of AC is not located exclusively in visual cortex (an empirical fact);

(5) the phenomenal character of perception cannot be produced exclusively in visual cortex (from 3 and 4);

(6) the phenomenal character of perception is consciousness-independent (from UPC);

(7) the activity in the neural basis of AC does not suffice for the phenomenal character to occur (from 6);

(8) the phenomenal character of colour perception is not produced in the subject (from 7).

6. Conclusion. As the argument illustrates, when UPC is considered against the background of overflow, naïve realism about colour turns out to be preferable over Rosenthal's reductionism. We thus have a case where empirical evidence rehabilitates the manifest image of the world.

References

Block, N. (2005). Two neural correlates of consciousness. Trends in Cognitive Sciences, 9(2), 46–52.

Block, N. (2011). Perceptual consciousness overflows cognitive access. Trends in Cognitive Sciences, 15(12), 567–575.

Kalderon, M. E. (2007). Color Pluralism. The Philosophical Review, 116(4), 563–601.

Moutoussis, K., & Zeki, S. (2002). The relationship between cortical activation and perception investigated with invisible stimuli. Proceedings of the National Academy of Sciences of the United States of America, 99(14), 9527–9532.

Norman, L. J., Akins, K., Heywood, A., & Kentridge, R. W. (2014). Color Constancy for an Unseen Surface. Current Biology, 24(23), 2822–2826.

Overgaard, M. (2018). Phenomenal Consciousness and Cognitive Access. Philosophical Transactions of the Royal Society B, 373. https://doi.org/10.1098/rstb.2017.0353

Phillips, I. (2016). No watershed for overflow: Recent work on the richness of consciousness. Philosophical Psychology, 29(2), 236–249.

Rosenthal, D. M. (2005). Sensory Quality and the Relocation Story. In Consciousness and Mind (pp. 149–174). Oxford: Clarendon Press.

Rosenthal, D. M. (2016). Quality Spaces, Relocation, and Grain. In J. R. O'Shea (Ed.), Sellars and his Legacy (pp. 149–185). Oxford University Press.

Weksler, A., Jacobson, H., & Bronfman, Z. Z. (2019). The transparency of experience and the neuroscience of attention. Synthese. https://doi.org/10.1007/s11229-019-02366-8