Dualism may sound like some irrelevant philosophical position, but most people (who grew up in the western world, at least) have a pretty intuitive concept of it. Basically, it is the idea that there are two “worlds” that exist in the universe, one physical, and the other one non-physical. The idea of this other world is where we get such concepts as the soul, free will, private phenomenon, consciousness, (absolute) morality, etc. There isn’t really a single name for this world, so I’m going to refer to it as the non-physical world to emphasize its mutual exclusivity from the physical world. (If they aren’t mutually exclusive what I have to say doesn’t apply; more on that later.)
The problem I see with this picture is how these two worlds interact. (Dualism assumes they do; if they didn’t, it would be indistinguishable from monism.) The physical world is presumably different than it would be if the non-physical world didn’t exist. Since the physical world includes everything that follows the laws of physics, this means that some physical entity is in a different state than it would have been had the non-physical world not existed. The only way for a physical entity to change its state from what it would have been to its present state is to interact with another physical entity; i.e. if something can change the state of a physical entity it must be physical itself. But this other entity we’re talking about is the non-physical world, which by definition isn’t physical! :eek:
To put this a little more concretely, suppose that scientists, in a previously undiscovered part of the brain, find a “black box” that is found to control consciousness and free will. There are three possibilities as to the status of this object: it is either non-physical, some combination of physical and non-physical and physical, or purely physical. We know it has to be at least part physical though, because the only way it would be able to control free will and consciousness is by communication to neurons through electrical signals, so we can eliminate the first option. If it were part physical and part non-physical, the second alternative, then all we would need to care about is the part of it that interacts with the physical world. We wouldn’t even be able to talk or think about the non-physical part, since talking and thinking are physical processes, so for all practical purposes we can disregard the non-physical part. That leaves us with the “black box” being either entirely physical, or else physically indistinguishable from being entirely physical, which is of course the same thing.
Let me give a couple of disclaimers about this line of argument. First of all, if the non-physical and the physical worlds don’t interact, or if information can only go from the physical world to the non-physical world but not the other way, this argument doesn’t apply. Of course since either way there is no possible difference in the physical world between the existence and non-existence of the non-physical world, we can just say it doesn’t exist to make things simpler. In addition, while I’ve worked this, and will continue to think about it, from the non-physical world to the physical, it also works the other way. I’ve been assuming that the physical world exists just because that’s the way I’m used to thinking about it, but it could be only the non-physical world that exists - as long as it isn’t dualism it doesn’t really matter.
Also, note that to be considered full-fledged dualism, something must be unexplainable in purely physical terms. Many more scientifically based philosophies explain concepts such as the soul and free will without going into dualism. What is important to realize is that our minds, always looking for patterns in things, invented those concepts, and while they are often convenient as shorthand for more complicated physical processes (many of which still don’t have scientific explanations), they didn’t exist before we put them there.
That might sound like a lot of exemptions, but there are many patterns of thought don’t fall into any of these categories. The one I’m thinking of specifically is this Judeo-Christian concept of absolute morality and good and evil. There is no way to represent these concepts in any kind of physical system. There are also of course lots of other branches of thought that involve dualism, including I think several other religions and in general anyone else who doesn’t think that all observable phenomenon have scientific explanations.
This line of argument has been pretty intuitively obvious to me for a long time, and a good portion of thinkers from the age of Enlightenment on have agreed with me, but I’m curious to hear from any dissenters.
(I hope this is clear enough for people to understand)
