Saturday, May 7, 2016
Philosophers who favor a supernatural or dualistic view of mind have contrived an argument that they think poses a major obstacle to physicalism. It is the so-called hard problem of consciousness, that claims there is an unbridgable gap between physical substance and mental substance. It is basically the claim that the stuff of conscious experience - the qualia, or qualitative component of consciousness - the texture of our perceptions - cannot be explained in terms of physical substances and phenomena. But this is an unscientific argument. It amounts to an argument from ignorance. It is saying that because we don't yet know how to fully explain consciousness in terms of physical matter and its properties, then there must be something immaterial about it. This fallacy gives courage to those (especially theists) who choose to ignore the track record of naturalistic science, and instead posit the existence of things like the immaterial soul as the answer to the problem.
I say this argument is contrived because it hinges largely on a matter of perspective. Our experience of the world by means of sensations is first-person, or subjective. It is necessarily true that we have our own experience of sensations, but we don't share those experiences with another person. The subjective perceptions of qualia occur within our own mind, not someone else's, because they are uniquely our own experiences. Even if we wired another person's sense organs to our brain, we would still have our own subjective experience of his sensations. There's no way we could say that one person's subjective experience of qualia is the same as the other person's. If I see redness, is it the same as the redness another person sees, or could it be that he sees something that I would call blue? We can't describe redness in an objective manner. The best we can do is to compare it to other things that are similar. But we can't give a fundamental description of redness that would be comprehensible to another person, such that he understands it independent of any reference to something in his own experience.
This is the basis of Thomas Nagel's argument. His discussion of what it's like to be a bat focuses on subjective experience, and our inability to make an objective description of it. There are facts about the bat's experience that are unknown to the rest of us, he says. And without an objective description, the phenomenon of conscious experience eludes science, he claims. But that is simply the reality of subjective experience. There's no reason to suppose, based on the inability to objectively describe what is inherently subjective, that science could never explain the existence of these experiences as physical phenomena.
David Chalmers makes an argument for the immaterial aspect of mind based on the conceivability philosophical zombies. A zombie is said to be physically identical to a human, but without the conscious experience of qualia. The zombie can see and hear, and respond to conversation in a way that is indistinguishable from an ordinary person, but without the qualitative feeling of sensations that humans experience as the substance normal consciousness. According to Chalmers, there is no physical difference, but the zombie lacks something else that is supposed to be the immaterial substance of mind.
Chalmers maintains that the experience of qualia is non-functional, and plays no role in physical causation. So the zombie can have sensations and react to them without ever having conscious awareness of their quality. But the zombie that can't experience qualia couldn't possibly behave the way conscious people do, because our behavior is intimately related to the qualitative feel of things. We are attracted to the pleasant taste of sugar, and repulsed by the rotten smell of garbage. We recoil from the unpleasant feeling of pain. If a zombie didn't experience these things, he wouldn't behave the way we do. Imagine a zombie holding his hand in a fire and saying "I can feel the sensation of pain, but there's nothing unpleasant about it."
Chalmers' thought experiment postulates something that sounds logically possible, but is actually incoherent. A zombie couldn't possibly behave in a way that is indistinguishable from a conscious person. First, the zombie must be able to sense things the way we do, or he wouldn't know anything about his surroundings. He wouldn't be able to converse, or to see what is in front of him. Second, the zombie must be able to distinguish the difference between different colors, sounds, smells, etc. If you place a red block and a blue block in front of him, and ask him to pick up the red one, he will correctly discern which one is red. But that ability do discern one color from another can only exist if there is something qualitatively different between them. That's precisely what we call qualia.
The bottom line is that we have every reason to think that the experience of sensations, that we call qualia, is very much a physical phenomenon, and that it plays a vital role in our ability to survive. The simple fact that we can't make an objective description of subjective experience is no reason to conclude that mind must be immaterial. The "hard problem of consciousness" only provides a weak excuse for dualists to hang on to their belief in the existence of something else for which there is no real evidence.