If physics says that objects are not colored, and light is not colored, what is colored? On what is color grounded?
Last May at UC Berkeley, a conference was held, “Grounding Sensible Qualities.” The introduction to the conference website discusses some key points from the current perspective of professional philosophy, and we hope the organizers won’t mind us including these few paragraphs here.
The project begins with the natural thought that an adequate account of sense perception—perception of a sensible world—is only possible once we have a satisfactory understanding of the nature of sensible qualities themselves.
During the Early Modern period, many philosophers, impressed by the discoveries of the Scientific Revolution, argued that colours must be mind-dependent—grounded in the mind, to put it in modern parlance. On such views, colours were either ideas in the mind (for Berkeley or Hume), or powers to cause experiences (for Descartes and Locke). More recently, however, this kind of subjectivist account of colour has fallen out of favor. Many philosophers now insist that sensible qualities are properties of ordinary medium-sized physical objects; that such physical objects retain their colours in the absence of any minds; and that, therefore, colours must be fully grounded in the external material world.
Despite the current popularity of the thesis that colours are mind-independent properties of material bodies, the traditional Early Modern view was not without its motivations. If we grant the pre-theoretically powerful intuition that we can become aware of essentially qualitative colours, sounds and tastes in hallucinations or in experiences of phosphenes or afterimages—experiences that lack any suitable material objects of awareness—we are naturally driven to the view that such qualitative properties cannot be grounded in the ordinary objects of the material world (for if they were, how could they be instantiated in the absence of their grounds?) and must instead be grounded in the mind.
Our methodological approach is to be inclusive of both sides of this debate. While philosophers have typically drawn a strict line between the kinds of properties—mass, charge, spin etc.—that inhere in material objects and the itches, pains and tickles that are by their nature dependent on our minds, we are interested in exploring the view that secondary qualities like colour straddle this ontological divide. This hypothesis receives prima facie support from the expansive range of entities to which we ordinarily attribute colours – a list that includes material bodies, lights, rainbows, phosphenes and after-images. In the background of these metaphysical investigations lies the question: Can an ontologically flexible view of colour give us a more satisfying account of colour perception?
While the Scientific Revolution of the Early Modern period led many philosophers to argue that colours were grounded in our awareness of them, no such challenge from Early Modern science threatened the naïve conception of shape properties as grounded in the physical world. But in the contemporary context, where Einsteinian relativity and quantum mechanics have both called into question the views of spatial properties endorsed by the Early Moderns, we can no longer see macroscopic shape properties as unproblematically grounded in the external world.
Faced with this challenge, one reaction would be to extend the Early Modern thesis of mind-dependence—the claim that sensible qualities like colours are grounded not in the world but in our minds—to shapes. A historical precedent for such a move can be found in Kant and his interpreters. Strawson (1966) suggests that the Euclidean shapes we encounter in experience are to be taken as features of phenomenal, rather than physical, space – as grounded in our minds’ cognitive architecture, rather than in the external world’s physical matter.
Such a view presupposes that the Euclidean space we fail to find in the contemporary description of the external world is instead present in our experience. But relocating Euclidean space in this way opens up another challenge, from a different branch of contemporary science: many results in perceptual psychology are taken to show that visual space is not in fact Euclidean. Empirical data suggest that subjects’ judgments about key geometrical features of “visual objects”—such as whether two arrays of lights form parallel lines—fail to conform to Euclid’s postulates.
Combined, the challenges from contemporary physics and psychology would seem to leave no suitable grounds for the Euclidean shape properties traditionally thought to characterize the objects of our perceptual experience. We will investigate how these challenges might be addressed, and what implications our contemporary scientific worldview might have for theories of shape perception.
BQTA: Phenomena like hallucinations, phosphenes and after-images are useful to illustrate the color puzzle. The main motivation for the traditional Early Modern view— as well as the current scientific view— is the conclusion apparently compelled by physics that the mind-independent world does not contain color, as explained by Steve Palmer.
The Early Modern idea, championed by John Locke, was to distinguish primary and secondary qualities in objects. The primary qualities are those recognized by physics, such as mass, charge spin, solidity, extension, motion, number, structure and shape. These are the properties of things in themselves which exist independently of us. The primary qualitites produce sensations in observers. Those are the secondary qualities, such as color, sound, taste, smell, hot/cold, etc. These qualities do not exist in the mind-independent world. The distinction has been much criticized, starting in the 17th century. The conference shows that independence of even such a core primary quality as shape may be problematic.
Since there is color all around us, and it’s not part of the physical world, there must be a separate mental world grounding not just color, but also sound, taste, smell, etc. This leads to seemingly insoluble problems, such as the idea that the world we experience is not the world that really exists, which is part of why it has fallen out of favor with most philosophers now. Scientists seem unaware of any problems, then or now.
As bonus coverage of the conference, we have some introductory comments from one of the papers.
Brian Cutter “Paradise Regained: A Non-Reductive Realist Account of the Sensible Qualities” (penultimate draft, forthcoming in Australasian Journal of Philosophy).
Sensory experience acquaints us with the sensible qualities: shape, colour, pitch, loudness, flavour, heat, cold, and others. These qualities, in all their manifest qualitative richness, appear to be exemplified in our environment. In the Garden of Eden, our divines tell us, things did not just appear so, but were so. According to Chalmers’s [“Perception and the Fall from Eden” 2006: 46] fable, ‘when an apple in Eden looked red to us, the apple was gloriously, perfectly, and primitively red.’ The redness of the apple was not a ‘microphysical property, or a disposition, or an unspecified property that plays an appropriate causal role’, but rather ‘a simple qualitative property, with a distinctive sensuous nature’ [ibid.: 66]. Then, we are told, came the Fall. First we ate from the Tree of Illusion. We learned that experience does not always present the world as it really is. Second, and far more importantly, we ate from the Tree of Science:
[…] we found that when we see an object, there is always a causal chain involving the transmission of light from the object to the retina, and the transmission of electrical activity from the retina to the brain. This chain was triggered by microphysical properties whose connection to the qualities of our experience seemed entirely contingent. So there was no longer reason to believe in acquaintance with the glorious primitive properties of Eden, and there was no good reason to believe that objects in the world had these properties at all. [ibid.: 49–50]
As a consequence of eating from the Tree of Illusion and the Tree of Science, so the story goes, the world was drained of its rich qualitative splendour. All colour, all sweetness, each whistling pitch and rosy scent was banished from the world, living on only in the representational content of experience. Long have our divines told this tale of paradise lost. This essay proclaims the good news of paradise regained: the world is Edenic, not merely in appearance but in reality.
BQTA: By “our divines” Cutter presumably refers to most philosophy since the 17th century. Cutter “defends a non-reductive realist view of the sensible qualities—roughly, the view that the sensible qualities are (i) really instantiated by the external objects of perception, and (ii) not reducible to response-independent physical properties or response-dependent relational properties.” He calls his theory “Secondary Quality Russellian Monism”. Does he regain paradise?