Second (and related), qualia are arguably ineffable; that is, they cannot neatly be put into words. Imagine trying to explain to a person who is blind what red looks like, or (a less extreme example) conveying to a lifelong vegetarian what tuna tastes like. While in both cases, we might attempt to use metaphors (“red is like a trumpet”) to convey the character of the experience, our attempts to do so will inevitably fail to do justice to the relevant sensation.
A final alleged property is that qualia are immediately and fully apprehensible to us just by experiencing them. In this respect, they are distinct from the objects of our experience. Imagine that you are lying in bed at night and hear a soft thud. You may well wonder what the noise was: a falling object, a door slamming in the wind, or perhaps your housemate returning home. What you don’t have to speculate about, however, is what the noise sounded like to you. This is something you grasped simply by hearing it. More strongly and more controversially, some philosophers have suggested that we can never make errors of judgment about our qualia. If I say something feels painful to me, for example, then it is nonsensical to suggest I might be in error.
Qualia and the Mind-Body Problem
One reason qualia have so fascinated philosophers is that they are arguably hard to explain in standard scientific terms. Many of us have probably heard neuroscientists talking about things like synapses, neurons, and different regions of the brain. It is perhaps not too difficult to see how this kind of scientific approach might explain various aspects of our behavior. We might understand perception, for example, in terms of the transmission of information from the sense organs through various processing areas of the brain, or unusual aggression in terms of the release of some hormone or neurotransmitter. It is much harder to see, however, how these kinds of scientific descriptions could ever give us a satisfying explanation of why red looks the specific way that it does, or why cinnamon tastes like this and vanilla like that.
The challenge here is not merely to explain the neuroscience of how vision works or how our tongue relates flavour information to the brain. Important progress is being made every day in understanding questions like these, although the science still has a long way to go. Instead, the real difficulty is that while science tells us about how the brain works, it seems unable to tell us what experiences are actually like. To get an idea of the problem, imagine a person who has been completely deaf since birth who wants to know what Beethoven sounds like. Even if we had perfect brain-scanners and could show them exactly what happens to someone’s neurons when they listen to music, it does not seem like this could ever properly convey to them the subjective experience of hearing the opening bars of the Choral Symphony.
This creates an apparent challenge for a scientific worldview. If science cannot fully explain qualia, then does it follow that science can only offer us a partial understanding of the universe? More strongly, one might wonder whether the seeming inexplicability of qualia in scientific terms shows that the universe we inhabit does not consist solely of things like atoms, molecules, forces, and other objects from the domain of science, but also contains distinctive, irreducibly mental phenomena.
The challenge is well illustrated by a famous thought experiment called “Mary’s Room” developed by philosopher Frank Jackson (1982).1 Imagine a woman called Mary who is a brilliant scientist. Specifically, we are told that she knows all the physical facts about color perception: she knows all about the physics of light, the biology of the eye, and the neuroscience of color processing in the brain.
- Mary’s Room is also discussed in Chapter 4.