“Hey, heads up, guys. Here comes Substance Dualism”
If contemporary philosophy were a high school and theories were students, Substance Dualism would be the kid who has a reputation for bad breath, horrible fashion sense, a shady family history, and for saying gauche and tactless things on a regular basis. The cool kids wouldn’t be caught dead talking to him, and others would avoid him assiduously. If any were unfortunate enough to come in contact with him, they’d dismiss him with a patronizing smile. “See that kid over there? That’s S.D. He’s mostly harmless, but, man, he has some crazy ideas. Everyone knows who he is, but no one pays him much regard.”
In the cafeteria of Philosophy High School, Substance Dualism eats alone.
Substance dualism, for those who aren’t familiar, is the view that humans are composed of two distinct substances—an immaterial mind (or soul) and a physical body. This view, or something like it, is the “common sense” belief held by the vast majority of people, both throughout history and across the world today. But, as anyone who’s taken an introductory course in the philosophy of mind knows, substance dualism is, as Jaegwon Kim puts it, “not a live option” for most contemporary philosophers. The majority view is materialism, alternatively known as physicalism, which holds that humans are composed solely of matter, and that the mind is either strictly physical or strictly supervenient (dependent) on the physical brain. We are, in the words of Marvin Minsky, “computers made of meat.”
Thankfully, philosophy is not a high school, and theories are not judged by popularity contests…or, at least, they shouldn’t be. Substance dualism’s unpopularity is irrelevant to whether it is true or false. Our concern should be with the reasons to accept or reject it, and we should do our best to eschew argumentum ad (un)populam.
So, what are the reasons that most contemporary philosophers reject substance dualism in favour of materialism? Surely there are very strong reasons against it (beyond its horrible fashion sense)?
As I see it, there are three main reasons philosophers reject substance dualism: First, discoveries in neuroscience have ostensibly removed the need to posit an immaterial mind. Brain researchers have established links between what we think, dream, and experience, and the immensely complex whir of processing in our brain. Our mental activity appears to be strictly correlated with neuronal activity.
Second, dualism is a more metaphysically complex theory than materialism. Ockham’s razor dictates that we choose the metaphysically simpler theory (materialism) over the more complex (dualism), provided the simpler theory explains the phenomena in question equally well.
Lastly—and this is the whopper—the interaction between the mind and brain is seemingly inexplicable if the mind is not physical. How does the immaterial mind interact with the physical brain? If the mind has no mass, charge, or extension in space, how can it cause neurons in the brain to fire? And how could neurons in the brain cause changes in the immaterial mind? This last consideration, known as the “interaction problem,” is the most cited reason for rejecting substance dualism.
In a series of three posts, I will evaluate each of these three main objections in turn. I will argue that they are, all things considered, not the decisive reasons to reject substance dualism that so many take them to be—especially in comparison with the problems facing materialism.
So, what do you think? Is this a fair list of the major objections against substance dualism? Are there other objections that I should address?