Causally Close Minded
The causal closure argument against interactionism is straightforwardly question-begging
“Now that everyone’s gotten their memorized preprepared slogans out of the way, we can actually have a real discussion.”
—Vivek Ramaswamy
Imagine someone made the following argument against theism:
There are no disembodied minds.
If God existed, he’d be a disembodied mind.
Therefore, God doesn’t exist.
This would be a terrible argument. Premise 1 is flagrantly question-begging—it amounts to “no beings like God exist,” which obviously a theist would reject. No person has any reason to accept the first premise unless they accept the conclusion. Of course, there might be arguments for why disembodied minds are impossible in principle, which could have some force, but if the claim is merely that disembodied minds are possible but nonactual, well, that’s obviously unconvincing.
And yet people make an argument against interactionist dualism that is equally unpersuasive and question-begging. For those who have been sleeping under a rock—by which I mean not up to date on very specific views about philosophy of mind—interactionist dualism claims that consciousness is nonphysical—meaning it’s not purely explainable in terms of the movement of atoms—and that it is causally efficacious, meaning that it causes things. Thus, the interactionist thinks that your thought that you want your arm to go upwards causes your arm to go upwards but is not reducible to the movement of atoms.
Perhaps the most popular response to interactionism involves claiming that it violates causal closure of the physical. The causal closure principle says that every physical effect has a physical cause. So it claims that nothing nonphysical causes anything.
But this is straightforwardly question-begging. One would only accept that non-physical things don’t cause things if they don’t think the mind is non-physical and causally efficacious. The view amounts to little more than stating that you don’t think interactionist dualism is true. No interactionist dualist has any reason to accept it!
It would be one thing if there was some in-principle impossibility involved in nonphysical things having causal effects. But any argument for that conclusion would be an argument against interactionist dualism. You don’t need to appeal to causal closure—you can just make the argument for why nonphysical causes are impossible (of course, I don’t think any such argument succeeds).
Of course, there’s nothing wrong with including causal closure in an argument against interactionist dualism. Sometimes, to make an argument valid, it has to have one premise that almost begs the question. But to think of causal closure as an argument rather than a statement of the conclusion is absurd!
In fact, one can create a parody argument for interactionist dualism called the argument from causal openness.
Everything nonphysical that exists in time is causally efficacious.
Consciousness is nonphysical and exists in time.
Therefore, consciousness is causally efficacious and nonphysical.
Therefore, interactionist dualism is true.
This is a terrible argument. Epiphenomenalists would reject 1 and physicalists would reject 2. It amounts to little more than stating that every other position is wrong. So why in the world is its twin considered the go-to argument against interactionist dualism?
When defending the causal closure premise, people often appeal to induction from other domains. They note that we’ve never observed any nonphysical cause. But the interactionist disputes this—they say we have observed a nonphysical cause. It’s called consciousness.
In order to avoid question-begging, the physicalist could claim that we’ve never observed any other nonphysical cause. But the interactionist dualist agrees with this. They think that consciousness is the only nonphysical thing that is concrete and exists in time, so it’s no surprise that there aren’t other nonphysical causes. Consciousness is the strangest and most unique phenomenon in the universe, according to the dualist, so it’s no surprise that generalizations about it from numbers and angels and modal facts would produce incorrect results.
So why is this argument convincing to many people? I do not know, but if anyone does, help me fill in. Some hypotheses:
Violating causal closure has unscientific vibes. It just sort of sounds mystical to think that nonphysical things move around atoms.
Violating causal closure it jarring in that it sounds like one is disagreeing with physicists. After all, they are denying that physics works the same way in the brain as it does out of the brain. Saying to a physicist “I think your core theory breaks down in the brain,” sounds sort of arrogant—oh, so you’ve deduced from purely philosophical argument that someone’s physics is wrong.
But I don’t think these worries are legitimate. The reason I don’t believe in ghosts or fairies or psychic powers is not that they’re impossible in principle, but instead that there aren’t good reasons to believe in them. In contrast, there are good reasons to believe in consciousness—it’s the most certain thing in the universe—and that it can’t be physical. Once we accept that consciousness isn’t physical, then there are certain advantages to positing that it’s causally efficacious—it might help explain, for instance, our talk about consciousness.
Physicists haven’t verified that the core theory works the same way in the brain. So interactionists are not disagreeing with the experimental results of the physicists—they merely claiming that it doesn’t hold in a case where we have no evidence that it does hold, where there are lots of philosophical reasons to think it doesn’t. I’m not decided between interactionism and epiphenomenalism, but I think interactionism is at least on the table.
Maybe the worry is more broadly with using philosophical arguments to make empirical predictions. One might think that interactionism is reminiscent of the ancients, who claimed they could deduce a priori that the world was made of air or water.
But clearly, we can use philosophical arguments to make some empirical predictions. On account of purely philosophical argument, I am very confident that we will never find a square circle anywhere in the universe. This is not because of empirical investigation, but instead because I think things can’t have contradictory properties. Similarly, I think we will never find the laws of mathematics breaking down or agony that is noninstrumentally good.
This charge is especially puzzling when raised by epiphenomenalists. Epiphenomenalists think that we can a priori know that consciousness is nonphysical. But once we’ve posited nonphysical consciousness, it can clearly feature in the best explanation of various physical phenomena! Once you’ve posited something not entailed by physics, it’s perfectly kosher to think it does something!
Ultimately, the causal closure “argument” amounts to little more than a question-begging talking point. Interactionists have nothing to fear from denying it!
I like the 'evidential' version of the argument suggested by Both Sides Brigade's comment. It just seems incredible (given our current scientific knowledge) to think that physical causes are insufficient to explain the functioning of our brains and bodies, or that non-physical stuff intervenes in the domain of physics. I can't take that seriously. So that's why I find interactionist dualism non-credible.
Is it "question begging"? I guess it depends whether some people may be initially drawn to interactionism without attending to these theoretical costs. They're pretty blatant, it's true, but people do sometimes overlook obvious things, so it still seems worth highlighting.
Compare the argument against cultural relativism from the objective wrongness of genocide. It's "question begging" in the same way -- it would seem so to a sophisticated defender of the view. But it still (rightly!) persuades many students who were initially drawn to relativism, because they just hadn't thought about this obvious problem with their view.
I think causal closure arguments are popular primarily because so many people have the general notion that we shouldn't carve out exceptions to an extremely well-confirmed theory with tremendous explanatory power merely because we encounter a specific case in which a poorly understood phenomenon fails, at first glance, to adhere to it. I'm sure dualists are sick of this comparison, but it's a lot like the debate over vitalism in the 19th century - in that case, "All matter is governed entirely by physical and chemical laws" was begging the question against vitalists, but the persuasive power of that premise nonetheless animated many of the most powerful arguments against vitalism and we all now look back and realize the vitalists were rash in dismissing it. I don't think these nominally question-begging arguments are really meant to be convincing on their own. They're more meant to foreground the high cost of the competing theory. Maybe it would be better to think of an Evidential Argument From Causal Closure that goes something like :
1) All well-understood phenomena adheres to causal closure.
2) Consciousness is a poorly understood phenomenon.
3) If all phenomena adheres to a particular principle, with the exception of a single poorly understood phenomenon that appears not to, then it is more likely that we are misunderstanding the single poorly understood phenomenon than that the particular principle is false.
4) It is more likely that we are misunderstanding consciousness than that causal closure is false.
5) We are justified in believing that causal closure is true.
6) We are justified in believing interactionist dualism is false.
Of course, a dualist can just insist that their introspective awareness of consciousness is such that they simply cannot be mistaken and they are therefore justified in dismissing the general principle no matter how solid it seems elsewhere - much like a Christian could insist that their introspective awareness of Jesus' love is such that they simply cannot be mistaken and they are therefore justified in dismissing the idea that no one comes back to life after being dead for three days. But I definitely find that baffling, both because the introspective awareness of consciousness I do have gives me many reasons to believe it is illusory in many important respects and because my other views about evolution and human psychology give me no reason to believe introspection would reveal the true nature of my consciousness anyway. But of course that's a broader debate!