I just returned from an interdisciplinary workshop on color (More or Less: Varieties of Human Cortical Color Vision). Unfortunately I was not able to attend the conference that followed. Below are a few scattered (jet-lagged) thoughts in reflection of what happened.

The workshop began with presentations by Michael Tye and Alex Bryne on the philosophy of color. Tye went over the basic positions in the metaphysics of color, viz. realism (colors exist on the surfaces of objects), irrealism (colors exist in the mind of the perceiver), and super-duper irrealism (colors do not exist anywhere). The talks were uninteresting if you, like I, were already aware of this stuff and the arguments on each side but it would have been useful (if that is the right word) for, say, a scientist who wasn’t.

During the discussion Tye and various commenters, were arguing about the relative costs and benefits of the various theories. Tye seemed to think that we should opt for the theory with the most benefits and the least costs. Byrne objected and memorably said “the truth has no costs”. If, for instance, color physicalism is true (colors just are physical properties of the surfaces of objects) then there are no costs in accepting that theory. As a group we may not know which theory is true but, he went on, this is compatible with some particular philosopher, or even a scientist I suppose, knowing the truth. I am pretty sure that it was this line of argument which prompted some unnamed scientist to quip that “the philosophers here are arrogant” later that day. But at any rate what are to make of this debacle?

It has always seemed to me to be obvious that realism and irrealism are true in this case. We use color words interchangeably for both properties of surfaces and also for the conscious color experiences we enjoy. So, when someone asks the question ‘what is red, really?’ they are asking a question which is ambiguous. ‘Red’ really is some physical property of a surface if what you are asking is ‘what is the perceptible property red?’ and it really is a property of some conscious experience if we are asking the question ‘what is the perceived property red?’ Each of these deserves to be called ‘the color red’. But, as between the various ways of spelling out the former or latter who knows? Is perceptible red a complex or primitive property? If primitive is it metaphysically primitive or only nomologically? My money is on complex non-primitive because of considerations about science but this is an open question for me.

It seems to me that the main reason for objecting to this common sense way of thinking about the color red is because of theoretical concerns about transparency. If one is convinced that one can *never* become aware of properties of our conscious experience but, instead, are only able to become aware of the properties ‘out there’. I thought that some of the interesting empirical results about synesthesia presented by Noam Sagiv called this into question. Some synesthetes see the color of a given number, say, as being ‘on the number’ (associators) whereas others see the color not on the number but rather as a property of their experience of the number (projectors). Of course, to get subjects to make this distinction took training, and so no one should deny that in teh first instance what we are usually aware of are the properties of objects but with training we can become aware of properties of our experiences. This distinction also nicely illustrates the way that we use color words to apply to both kinds of things (objects and experiences).

Charles Hayward and Robert Kentridge presented interesting data on cerebral achromatopsia, which is color blindness due to cortical damage rather than any deficiency in the eyes or LGN. One of their main points seemed to be to distinguish CA from blindsight for color. So, cerebral achromatopsics are unable to access or use any information about the color of objects. It is not, like blindsight, that they (seem) to lack phenomenology but are able to use the information to make judgements that are mostly accurate. These subjects lack any ability to access color information. Most interestingly there was one patient who had CA but who did not notice the deficit at first. Presumably this person had all of the color phenomenology just vanish and yet he did not seem to notice. Perhaps even more surprising was the fact that it was not until there color vision had been restored that they noticed that it had been gone in the first place!

There is a lot more that happened (like Mel Goodale’s talk which was excellent) but I’ll have to think about that later!