To: Anna H.
From: Geoffrey Klempner
Subject: Why are philosophers interested in qualia?
Date: 4th April 2011 13:10

Dear Anna,

Thank you for your email of 22 March, with your fourth essay for the Philosophy of Mind program, in response to the question, 'Define a 'quale' giving some examples of qualia. What is the philosophical interest in the notion of a quale?'

This is a very good essay which shows a vivid appreciation of the philosophical question concerning the nature of subjective experience, which the notion of a quale is intended to answer. Are qualia real or are they mere figments of the imagination? From either alternative, consequences follow.

If qualia are real, then it follows that no-one can know what another person's experience is 'like'. As you state, 'Qualia are therefore totally private, individual experiences: idiosyncratic. My quale of red and my quale of sweet are distinguishable and distinct from anyone else's red or sweet quale.' In other words, I don't know what 'red' or 'sweet' are like for you. Maybe my 'red' is your 'blue' and my 'sweet' is your 'salty'.

But as you go on to observe, 'If we can further affirm that a quale can become inverted or that a supposedly same quale can be of a different nature at different times, does this make a quale more of a figment of the imagination?' In other words, we can repeat what I said in the previous paragraph about 'I' and 'you' substituting 'I at time time1' and 'I at time time2'. My qualia could keep changing from moment to moment, and I would never know the difference.

Rebounding from this, the alternative view would be that qualia are merely figments of the imagination. But now we need to say more. One might be tempted to say that, because qualia are mere figments of the imagination, there really are no such things as the experience of red or sweet. If that is the case, if there really isn't anything that is 'red' or 'sweet', then most of the things that we normally say about our experience are false. In fact, one could go further and infer that if there isn't anything that is 'red' or 'sweet' then it is false that we have 'experience'! Which seems an absurd conclusion.

So what is it to experience 'red' or 'sweet'? We have the scientific account: red objects are those objects whose surface reflects a particular wavelength or range of wavelengths of light which interact with the 'cones' in the retina responsible for the experience we call 'red'. Sweet substances are those substances whose chemical properties are such that, when dissolved in saliva, they excite the taste buds responsible for recognizing a food as 'sweet'. Wavelengths of light, chemical properties, retinal cones, taste buds are all physical entities. The world is a physical world. There is nothing red or sweet in the physical world. These are just terms that we erroneously use, as if they named something real, when in reality they do not.

That's a possible philosophical position with respect to the mind-body problem. The technical term is eliminative materialism. This is an example of what philosophers term an 'error theory'. Mental properties are 'eliminated' in favour of physical properties. One of the things that the error theory is required to explain, however, is why we make this error. It is necessary that we (falsely) believe that we have 'experiences', that there are things that are 'red' or 'sweet', in order for there to be language and communication. The existence of 'qualia' is a necessary illusion.

However, I don't agree that that's the only available choice for someone who rejects qualia. In the program, I take a less extreme line. I would define 'red' as follows. An object is red if and only if observers who are not colour blind viewing the object under normal light conditions agree in calling the object 'red'. A substance is sweet if and only if competent tasters tasting the substance under normal conditions agree in calling the substance 'sweet'. According to these definitions, it is true that some objects are red and that some substances are sweet.

The subtle point about these definitions is that there is no assumption about the physical story behind our experiences of red or sweet. In a possible world created by a benign deity, where there were no underlying physical explanations (because God does all the work), there would still be red roses and sweet chocolate. There would, however, be no way to do science (as we know it), because there would be nothing 'underneath' our familiar experience of the world for science to uncover. But there would still be truths about experience.

I have argued this point with philosophers who take a different line. They would say that in the world I have described, there cannot be any truths about experience. There has to be an underlying physical story, in terms of the microstructural properties of physical objects. Whereas in my story, all that is necessary is that there be intelligent, living beings who move, speak and behave as we move, speak and behave. I don't have a knock-out argument in favour of my view, but I also don't see that the alternative view can be proven either.

All the best,

Geoffrey