This is the 50th post in my Theories of Knowledge and Reality series. The last post looked at the interaction problem, which is raised against the standard form of substance dualism known as interactionism. This post moves to a different form of dualism, property dualism or epiphenomenalism.
According to this view, the physical does cause the mental, but no mental event causes any physical event. The physical world gives rise to mental activity, but there's nothing going the other way. It's sort of like a free rider. Whenever brains are constructed in the right way, thoughts happen. Brains have mental properties, and there's nothing physical about these properties. This view doesn't assume any soul-like mind as a substance. There doesn't have to be any thing that's non-physical. Because of this, the view is often called property dualism (as opposed to substance dualism). This view avoids the problems of interaction (at least the problem with the conservation laws) and the problem of simpler views being more likely, since the mental things don't exist according to property dualism. This view agrees with materialism about which things really exist. The strangest thing about the view is that it's got one feature in common with parallelism - the mental stuff doesn't do anything. Nothing in the world is caused by it. So your thoughts don't affect anything. It's worth thinking about which objections to parallelism also apply here.
The Mutant and Zombie cases to illustrate this view (I believe David Lewis first used the term 'mutant' this way, and David Chalmers seems to be the one who coined the philosophical use of 'zombie' in this way). Mutants are just like normal people physically but have different qualitative experiences. Some of them have their colors reversed. When a color mutant sees what we see as red, she says it's red but sees it the way we see blue. When she sees what we see as yellow, she says it's yellow but sees it the way we see orange. Is there any way we could know that such a thing was going on? Maybe it does occur. There's no way to rule it out. The same sort of thing could go on with the sense of taste (sweet and sour reversed, salty and bitter reversed), sound (high and low pitches reversed), or even touch (soft and hard, rough and smooth). Maybe even pain and pleasure could be reversed, with someone experiencing what we feel as pain but calling it pleasure and smiling, etc. This seems really weird, but if their physical makeup is just as ours, then they would smile and say it's good when they have the same brain state as we do when we experience pleasurable things. Yet maybe their internal feel is totally different. How would we know?
The zombie is someone who just has no internal feel whatsoever. The zombie experiences nothing, but we could never know. How do we know if anyone else even feels anything? They act the way we do when we experience things. They say things. They cry out in pain. They act overjoyed when things go really well for them. They talk about how great certain foods taste. But couldn't it be possible that they are just following a sort of programming? When their brain received certain input, it makes changes within the brain, and some of these affect what the body does as a response. Couldn't that occur without any actual sensation or experience?
Frank Jackson and Thomas Nagel believe both
zombies and mutants are possible (though probably not actual). They hold this
property dualist view. Their reasoning is that some things about our experience
can't be explained in physical terms, so there must be some non-physical properties.
They take this from Nagel's case of the impossibility of imagining a bat's
One problem with the materialist views is that they seem to leave out an important aspect of mentality - the inner feel of conscious experience. Nagel focuses on the question of what it is like to be a bat - to experience life with such different perceptual input from what we've got. It's something we can never know. Similar, men can never know what it's like for a woman to give birth or to experience the social and biological influences that affect how women think about the possibility of being raped. A white man can never know what it's like to grow up as black in the United States. Someone who has never experienced an orgasm cannot imagine what such an experience is like. Someone who has never been drunk or high doesn't know what that is like. Try imagining seeing a color besides the ones we've experienced. If there is a God and some people have genuine relationships with God, nonbelievers don't know what that experience is like. We can't even imagine going beyond our experience. These are facts about our inner mental life that we simply can't capture in terms that we can communicate to someone else. Facts about the first-person perspective seem to be left out of all the materialist views. Nagel suggests that dualism can capture what's missing.
Jackson gave a formal argument for exactly that thesis. I'll discuss that argument in the next post.