We’ve discussed different pictures dualists could have about mental/physical causation.
The most natural, intuitive view is that sometimes physical happenings cause mental happenings (for example, stepping on a nail causes you to feel pain), sometimes mental cause mental (pain causes anger), and sometimes mental cause physical (the anger causes your face to get red and for your body to move and shout towards your roommate). Views that allow for all these possibilities are called interactionist forms of dualism. Descartes held a view of this sort.
There are more exotic, far-out options for the dualist too.
Some views deny that there are any causal interactions in either direction, not from physical to mental nor from mental to physical. Descartes’s follower Malebranche held a very radical form of this, called “occasionalism.” The details of what he said aren’t important for us.
At the end of the Huxley reading we looked at, he defended the view that animals (“brutes”) and maybe humans too are “conscious automata.” What Huxley meant by that is that physical events can cause mental ones, but mental never causes physical. (Huxley doesn’t say whether mental events can cause other mental events.) This is a view that’s nowadays called epiphenomenalism. Huxley doesn’t use that label himself in the paper we’ll be reading. Also I don’t think he’s clearly a dualist in our sense: he doesn’t commit himself to the existence of souls, nor to their nonexistence.
These alternative views ask us to accept: the hurting quality of your pain does not cause you to yell. The itchiness of your back does not cause you to scratch. These claims are hard to believe.
That’s why our discussion is mostly going to focus on whether dualist interactionist views — the most natural view that a dualist could go for — are reasonable. Materialists have argued that these views are problematic.
This is van Inwagen’s 3rd argument against dualism (pp. 260–2); see also Gennaro pp. 36–39.
Suppose Alfred is operating a remote-control airplane, and a bird flies into the plane. This is likely to affect the plane’s performance, and Alfred’s ability to control it, but the crash won’t have any direct effect on Alfred. It won’t knock him unconscious, for instance. Similarly if the airplane flies through a cloud of corrosive gas.
This is the kind of situation we should expect if Alfred was something apart from his body. Why should hitting Alfred on the head cause him to become unconscious? Why shouldn’t it instead produce the following effects: Alfred feels a blow to his head, notices his body falling to the ground and no longer doing what he tells it, then he’s left floating in darkness but still conscious and able to muse about his condition. If Alfred’s body drinks alcohol, why aren’t the effects limited to Alfred’s body and his ability to control it?
The body and the mind don’t interact as we’d expect them to interact if the mind was something apart from the body, “remotely controlling” the body, as it were. The connection between them seems to be more intimate than that. The dualists owe us an explanation of why that should be so, if the soul is the independent substance they claim it to be.
It is difficult for dualists to give a coherent account of how there could be any causal interaction between the mental and the physical. For according to the dualists, this would be a matter of some non-physical thing, a soul, interacting with physical things. It is obscure how things with the peculiar properties souls have could exert any causal influence on our bodies. The soul isn’t extended (it takes up no physical space); it isn’t in contact with any bodies; and in itself it has no physical properties (no mass or momentum or electric charge). By what means could something like that causally interact with our bodies?
We’ll talk about three arguments pressing this kind of challenge.
First, there’s Princess Elisabeth of Bohemia’s challenge to her teacher Descartes. She argued that normally when one thing causes movement in a second thing, it has to push or touch the second thing. But how can a soul push or touch bodies, when it’s outside space?
Descartes thought we had to accept it as a fundamental, unexplained primitive idea that souls could causally affect bodies, at least at one central location. Elisabeth wasn’t satisfied with that.
The second argument under this heading is related to the first. We see this in the following passages from van Inwagen:
Other dualists… have rejected interactionism, generally because of the physical or metaphysical difficulties raised by the thesis that a non-physical thing (a thing having no physical properties like mass or electrical charge) could affect a physical thing. (p. 228)
We briefly mentioned in [the passage just quoted] some difficulties with the idea that a non-physical thing could affect a physical thing. Wouldn’t that require a violation of well-established physical conservation laws like the law of the conservation of energy and the law of the conservation of linear momentum? And isn’t it also far from clear how a physical thing could affect a non-physical thing? (p. 260)
also in these passages from Gennaro:
MARY: Dave, take my example from earlier. I kick you in the leg and you then must acknowledge the physical facts about what happens up through the nervous system and into the brain. But instead of simply admitting that the last neural firing in the causal sequence just is the pain you feel, you think that the last neural firing causes the further pain state in your nonphysical mind.
DAVE: Right. The mental state is not identical with the neural state, but rather is caused by it.
MARY: But how in the world does that happen?
DAVE: I don’t know, but that doesn’t mean it doesn’t happen that way.
STEVE: Doesn’t that bother you, Dave? Why believe that causation could even exist between such radically different substances? (p. 31)
STEVE: …I am still baffled about exactly how any dualist interaction could take place and that’s one reason why I often lean toward materialism.
DAVE: What’s the other reason? You said earlier you had two.
STEVE: Right. The second serious problem has to do with the apparent fact that dualist interactionism is inconsistent with the well-established scientific Conservation of Energy Principle, which says that the total amount of energy in the universe, or any controlled part of it, remains constant. So any loss of energy in a cause must be passed on as a corresponding gain of energy in the effect. The cue ball loses energy when it hits another ball, but the energy doesn’t magically disappear and go out of existence; it’s passed on to the other ball. In general, then, energy is neither created nor destroyed.
DAVE: So where’s the inconsistency?
STEVE: Interactionism claims that there is causation between the physical world and the nonphysical mental realm.
DAVE: Yes.
STEVE: But since minds wouldn’t be part of the physical world, there would then be sudden gains and losses in the amount of total energy whenever mental events caused physical events, or vice versa. That is, when a physical event caused a mental event, energy would literally go out of the physical world, since causation involves a transfer of energy from cause to effect. Conversely, when a mental event caused a physical event, there would have to be a gain of energy in the physical world.
MARY: Yes. This seems like a serious problem for you, Dave…
…
DAVE: Well, maybe the Conservation of Energy Principle isn’t true or is only true concerning purely physical objects without minds.
MARY: Are you serious? The principle is true everywhere in the entire universe, including among all other animals, but then does not apply only when humans are involved? Incredible! (pp. 33–34)
Gennaro suggests some different ways the dualist might respond, including:
DAVE: You mentioned the “transfer of energy from cause to effect,” and you have simply assumed it in your argument.
STEVE: Of course; that’s the way it works.
DAVE: No, that’s the way it works as far as we know in the physical world. Maybe it doesn’t always work that way. Or maybe causation between the physical and the nonphysical doesn’t involve a transfer of energy in the same way. After all, you’d expect it to be a bit different; wouldn’t you? So even if the level of energy does remain constant, as the Conservation Principle says, that may not really contradict interactionism. You must remember that it’s a principle of physics, which means that it may apply only in the physical world. Things may work quite differently with mental-physical interaction. (p. 34–35)
In class we may discuss some other challenges to the transfer-of-energy principle, even just restricted to the physical world, like this: Didn’t my alarm clock failing to go off cause me to be late for work? Yet it didn’t transfer any energy to me — that was the whole problem. Can the physicalists explain the difference between these cases, that seem ordinary and acceptable, from the kinds of cases the dualist wants, that the physicalist thinks are problematic?
The third argument under the heading of how the dualist can make sense of the mental/physical interface is presented only briefly in our readings. We see it in these few sentences from van Inwagen:
Here is another sort of “interaction” difficulty. The World, the dualist says, contains both non-physical persons and physical organisms. But how do a particular person and a particular organism become “associated”? What brings it about that Jane Tyler interacts with this human organism (the one we label ‘Jane Tyler’s body’ precisely because it is the one she interacts with)? (p. 260)
We’ll spell the reasoning here out more fully. It’s discussed at greater length in other texts, and sometimes is referred to as the Pairing Problem.
Consider that two guns A and B fire, and two people X and Y are killed. What could make it the case that the firing of gun A caused the death of X rather than the death of Y? The question may be a bit harder if gun A and gun B are physically the same as each other. (The same model guns.)
Note that we’re not asking how a detective could figure out or prove which gun killed which person. That’s an epistemological question. We’re asking something different. We’re asking, how can we make sense of there being an answer, even if no one ever knows what it is. Is there anything in reality that could make us be in the situation where it was gun A that killed person X and B that killed Y, rather than the other way around?
For guns, it’s natural to think that yes of course there’s an answer. There was a bullet that came out of gun A’s muzzle and then traveled through space until it hit X’s body. There wasn’t anything similar going on in the space between gun A and Y’s body.
And we’d expect a similar story to be available (that is, to have been out there in reality, even if no one is in a position to detect it anymore) whenever we have physical causation. The story about how one physical event causes another, and why it had this effect (death of person X) rather than this other effect (death of person Y) will have something to do with how the cause and the effect are related in space and time, and what happens in between them.
But now consider a case where we’ve got mental happenings in souls allegedly having effects on the physical world. Suppose we have soul A and soul B. It may make the case harder if they are mentally the same as each other. (Duplicate souls.) And we have one physical effect, that body C moves a certain way. Now again we ask: what could make it the case that it was what happened in soul A that caused body C to move, rather than what happened in soul B? (You can also add other bodies to the story if you want. But the main problem is already now on the table, with souls A and B and body C.)
Here the dualist can’t give the same kind of story we gave in the gun case. They can’t say “That’s explained by what happens in the spatiotemporal regions in between the happenings in soul A and body C.” They can’t say this because souls are supposed to be outside of space.
If we allowed the dualist to say that soul A affected some one part of the physical world, like Descartes’s pineal glands, then they could talk about what happens in space downstream from there. But how does that first instance of mental-to-physical causation work? Why was it what happened in soul A that affected body C’s pineal gland, rather than what happened in soul B?
Perhaps the dualist can come up with answers to these questions. But they do seem to be difficult challenges.
Epiphenomenalists avoid the questions as we’ve posed them because they deny that mental events ever cause physical ones. But dualists who take that strategy would have analogous trouble explaining why some physical events rather than others caused an effect in a particular soul.
This is summarizing material that we didn’t get to discuss yet in lecture, but will take up on Monday.
Our last argument has to do with the notion of too many causes, often expressed as “causal overdetermination”. It comes up only briefly in our readings, on pp. 32–33 of Gennaro. But many materialists believe this to be the most decisive objection or challenge to interactionist dualism.
Suppose these dualists are able to overcome the previous difficulties somehow. They find some way of explaining how it would be possible for there to be causal connections between the mental and the physical
Another problem for these dualists comes from the fact that we have good empirical evidence that nothing happens in or to a person’s body except what conforms to physical and chemical laws. The physical world seems to be causally closed: that is, for everything that happens in the physical world, there seems to be a wholly physical cause. There is no real scientific evidence that, in order to find a causal explanation of why your body moved in such-and-such ways, we have to appeal to “miracles” or any supernatural causes.
Maybe we have to make an exception for what happened at the start of time; but let’s ignore that.
As we’ll discuss later this semester, there are debates in the foundations of physics about whether our world is “deterministic”, that is, whether how it is at one moment leaves open only a single physical possibility about how it will be the next moment. Arguably the notion of “causal closure” can be understood in a way that leaves open that our world isn’t deterministic. The philosopher who thinks the physical world is “causally closed” can say, well there has to be a physical explanation of why it was 90% probable that our world evolved in one way rather than another.
Now it may make it sound like we’re begging the question against the dualist here. If the physical world is “causally closed,” doesn’t that already say that there can’t be non-physical causes of what happens in the physical world?
No, we’re not yet assuming that. The label “causal closure” for this thesis can be misleading. All that we’re saying is that if something physical happened, then there is a wholly physical causal explanation of it. That leaves open the possibility, at least for the sake of argument, that there may be other explanations too.
All we’re saying is that if the dualists want to say that the mental has causal effects on the physical, then they’re going to have to say that there are non-physical facts about us that play a role in causing our bodies to move in the ways they do, and also there are wholly physical causes for our bodies moving those ways too. That is, they’re going to have to say that our bodies’ movements are overcaused. Our bodies’ movements have two separate causes, each of which is sufficient to make those movements occur or at least explain why they had the probability of occurring that they did. This would be like a case where two assassins simultaneously shoot someone, and each bullet was sufficient to cause the victim’s death. In such a case, his death would be overcaused.
If interactionism is true, though, then every time the mental facts about you play a role in causing your body’s movements, those movements would be overcaused. This would be overcausation on a systematic and wide-scale basis. The second step in the materialist’s argument against the interactionist is that it’s hard to believe that there is so much overcausation going on.
What pre-ordained harmony keeps the mental causes and the physical causes aligned or “in synch” with each other? What would happen if the mental causes and the physical causes got out of alignment? How would our bodies move then?
Some observations:
Imagine that your friend Harry announces that he’s got telekinesis, or the power to move things without touching them, just by concentrating his mind in a special way (or using his wand, or whatever). Now in the real world, perhaps we’d already find that announcement incredible (unbelievable). But let’s make things easier for Harry and suppose that, in this scenario, we think some people actually are or might be telekinetic. But you never thought before that Harry was. He sees you have some doubts, and so offers to show his powers off. You say okay, why doesn’t he make the metal ball in this pinball machine roll into the flashing cup in the middle. So he scrunches his forehead, and lo and behold, the metal ball rolls into the flashing cup. Amazing! Except it turns out that this pinball machine also has lots of sensors and video cameras on it (like the black box in an airplane), and you sift through all the recorded information and it turns out that the metal ball was going to roll into the flashing cup anyway, just because of the direction and speed it was going, and how it bounced off the bumper on the left side, and so on. So Harry tries again. He scrunches his forehead and the metal ball goes through a loop-the-loop on the right side of the machine. Except, it turns out, that’s what it was going to do anyway, based on how it was already moving, and how the pinball machine is built, and so on. This keeps happening. Every time Harry tries to show off his telekinetic power, it turns out that the pinball was already on a course to do the same thing anyway, just because of the mechanics of the pinball machine. Harry says, Hey, that doesn’t prove he doesn’t have telekinesis, because maybe it just so happened that everything he made the pinball do, the machine also happened to make the ball do too. Some things have more than one cause. That’s true, you acknowledge, remembering the discussions of multiple assassins from your philosophy class. But probably, you’re going to be pretty doubtful at this point that Harry has the powers he claims to have.
In the same way, the materialist is doubtful that the dualist’s souls (which would be like Harry in the story) have the causal powers that the dualists claim they do, when all the movements of our bodies, our physical speech, and so on, can already be explained in physical terms (this would be like the pinball mechanics in the story with Harry).