One of the big problems I have with substance dualism is “how does the soul work?” With monist theories of mind, there are still plenty of unknowns, but there’s a large tapestry of interacting causes and effects we can trace. When someone gets brain damage in region X, it tends to cause problem Y. When there’s an amount of drug X in the system, the production of neurotransmitter Y is inhibited, reducing brain function Z. It’s a complex system, but from what I can tell, it has pretty good predictive value.
Not so much with the soul. It just does complex consciousness stuff without any explanation. You can call that a “mystery” but it says “brick wall!” to me. It doesn’t help that some people misunderstand and abuse Occam’s Razor to claim that souls should be favored as an explanation because they’re allegedly simple. If that were how Occam’s Razor worked, anything could be said to work through “simple” magic, and we’d get nowhere. It’s also heavily against what I’ve seen of the universe: Simple objects have simple interactions. It’s only when you have complex systems that complex behavior results. If you want to assert something so counter-intuitive, you’ll need something other than special pleading to convince me.
One common argument is an analogy: Brain damage, drugs, and such reduce conscious behavior because the brain is like a radio or television, and the soul is like a transmitter, so damage to the radio messes with the reception. I realize this is just an anecdotal account, but that certainly defies my experiences as a conscious person. When medication makes me sleepy, I’m not a fully awake, conscious person in the ether, trying to control a less responsive body, I get sleepy. I’m a teetotaler, so I’ve got to ask: When you get really drunk, are yelling at your body for making stupid decisions?
One persistent annoyance I have is that the non-physical substance posited by dualism is described in terms of what it’s not. Attempts at analogies comparing physical objects to other physical objects, like matter and energy, only serves to spread confusion while allegedly sounding profound. What’s the deal? Opposite that, I’ve seen a lot of assertions that “material” things like brains can’t have consciousness, with no explanation given. Why not? What identifiable properties or circumstances are preventing it?