Epiphenomenalism and epistemic changes wrought by experiences

Epiphenomenalists think that there are non-physical qualia that are causally inert: all causes are physical. The main reason epiphenomenalists have for supposing the existence of non-physical qualia is Jackson’s famous black-and-white Mary thought experiment. Mary is brought up in a black-and-white room, learns all physical truths about the world, and one day is shown a red tomato. It is alleged that before she is shown the red tomato, Mary doesn’t know what it’s like to see red, but of course once she’s been shown it, she knows it, like we all do. Since she didn’t know it before and yet knew all physical truths, it follows that the the fact about what it’s like to see red goes beyond physical reality.

Now, let’s fill out the thought experiment. After she has been shown the tomato, Mary is put back in the black-and-white room, and never again has any experiences of red. It seems clear that at this point, Mary still knows what it’s like to see red, just as we know what it’s like to see red when we are not occurrently experiencing red.

So, what happened to Mary must have changed her in some way: she now knows what it’s like to see red, but didn’t know it before.

But given epiphenomenalism, this change is problematic. For it seems that it isn’t the quale of red that has changed Mary, since qualia are causally inert. It seems that Mary was changed by the physical correlate of the experience of red, rather than by the experience of red itself.

However, if this is right, then imagine Mary’s twin Martha, who has almost exactly the same things happen to her. Martha is brought up in an exactly similar black-and-white room, then shown a red tomato, and then brought back to the room. There is, however, one curious difference. During the short period of time during which Martha is presented the tomato, a supernatural being turns her into a redness-zombie, by preventing her from having any phenomenal experiences of red, without affecting any of her physical states. Since on epiphenomenalism, the experience of red is causally inert, this makes no difference to Martha’s future intrinsic states. In particular, Martha thinks she knows what it’s like to see red, just as Mary does.

But it seems that epiphenomenalist who relies on the Mary thought experiment for the existence of qualia cannot afford to say that Martha knows what it’s like to see red. For Martha is a redness-zombie in the one crucial moment of her life when there is something red for her to see. If Martha can know what it’s like to see red, so can a permanent redness-zombie. And that doesn’t seem to fit with the intuitions of those who find the Mary thought experiment compelling.

The epiphenomenalist will thus say that after the tomato incident, Mary and Martha are exactly alike physically, and both think they know what it’s like to see red, but only Mary knows. Does Martha have a true opinion, but not knowledge? That can’t be right either, since someone who has true opinion but not knowledge can gain knowledge by being told by an epistemic authority that their opinion is true, and surely mere words won’t turn Martha into a knower of what it’s like to see red. The alleged difference between Martha and Mary is very puzzling.

There is a possible story the epiphenomenalist can tell. The epiphenomenalist could say that the physical correlates of her experience of red have caused Mary to have the ability to imagine red and have visual memories of red, and this ability makes Mary into a knower of what it’s like to see red. Since Martha had the same physical correlate, she also has the same imaginative and memory abilities, and hence knows what it’s like to see red. It may initially seem threatening to the epiphenomenalist that Martha has gained the knowledge of what it’s like to see red without an experience of red, but if she has gained this by becoming able to self-induce such experiences, this is perhaps not threatening.

But this story has one serious problem: it doesn’t work if both Mary and Martha are total color aphantasiacs, unable to imagine or visually imagine colors (either at all, or other than black and white). Could the epiphenomenalist say that a color aphantasiac doesn’t know what it’s like to see red when not having an occurrent experience of red? That could be claimed, but it seems implausible. (And it goes against The Shadow’s first-person testimony that they are an aphantasiac and yet know what it’s like to see green.)

Perhaps the epiphenomenalist’s best move would be to say that no one knows what it’s like to see red when not having an occurrent experience of red. But this does not seem intuitive. Moreover, the physicalist could then respond that the epiphenomenalist is confusing knowledge with occurrent experience.

All in all, I think it’s really hard for the epiphenomenalist to explain how Mary’s knowledge changed as a result of the tomato incident.

A weaker epiphenomenalism

A prominent objection to epiphenomenalist theories of qualia, on which qualia have no causal efficacy, is that then we have no way of knowing that we had a quale of red. For a redness-zombie, who has no quale of red, would have the very same “I am having a quale of red” thought as me, since my “I am having a quale of red” thought is not caused by the quale of red.

There is a slight tweak to epiphenomanalism that escapes this objection, and the tweaked theory seems worth some consideration. Instead of saying that qualia have no causal efficacy, on our weaker epiphenomenalism we say that qualia have no physical effects. We can then say that my “I am having a quale of red” thought is composed of two components: one of these components is a physical state ϕ₂ and the other is a quale q₂ constituting the subjective feeling of thinking that I am having a quale of red. After all, conscious thoughts plainly have qualia, just as perceptions do, if there are qualia at all. We can now say that the physical state ϕ₂ is caused by the physical correlate ϕ₁ of the quale of red, while the quale q₂ is wholly or partly caused by the quale q₁ of red.

As a result, my conscious thought “I am having a quale of red” would not have occurred if I lacked the quale of red. All that would have occurred would be the physical part of the conscious thought, ϕ₂, which physical part is what is responsible for further physical effects (such as my saying that I am having a quale of red).

If this is right, then the induced skepticism about qualia will be limited to skepticism with respect to unconscious thoughts about qualia. And that’s not much of a skepticism!

Knowledge of qualia

Suppose epiphenomenalism is true about qualia, so qualia are nonphysical properties that have no causal impact on anything. Let w₀ be the actual world and let w₁ be a world which is exactly like the actual world, except that (a) there are no qualia (so it’s a zombie world) and (b) instead of qualia, there are causally inefficacious nonphysical properties that have a logical structure isomorphic to the qualia of our world, and that occur in the corresponding places in the spatiotemporal and causal nexuses. Call these properties “epis”.

The following seems pretty obvious to me:

1. In w₁, nobody knows about the epis.

But the relationship of our beliefs about qualia to the qualia themselves seems to be exactly like the relationship of the denizens of w₁ to the epis. In particular, neither are any of their beliefs caused by the obtaining of epis, nor are any of our beliefs caused by the obtaining of qualia, since both are epiphenomenal. So, plausibly:

2. If in w₁, nobody knows about the epis, then in w₀, nobody knows about the qualia.

Conclusion:

3. Nobody knows about the qualia.

But of course we do! So epiphenomenalism is false.

The traveling minds interpretation of indeterministic theories

I'm going to start by offering a simple way—likely not original, but even if so, not very widely discussed—of turning an indeterministic physical theory into a deterministic physical theory with an indeterministic dualist metaphysics. While I do not claim, and indeed rather doubt, that the result correctly describes our world, the availability of this theory has some rather interesting implications for the mind-body and free will and determinism debates.

Start with any indeterministic theory that we can diagram as a branching structure. The first diagram illustrates such a theory. The fat red line is how things go. The thin black dotted lines are how things might have gone but didn't. At each node, things might go one way or another, and presumably the theory specifies the transition probabilities—the chances of going into the different branches. The distinction between the selected branches and the unselected branches is that between the actual and the merely possible.

The Everett many-worlds interpretation of Quantum Mechanics then provides us with a way of making an indeterministic theory deterministic. We simply suppose that all the branches are selected. When we get to a node, the world splits, and so do we its observers. All the lines are now fat and red: they are all taken. There are some rather serious probabilistic problems with the Everett interpretation—it works best if the probabilities of each branch coming out of a node are equal, but in general we would not expect this to be true. Also, there are serious ethics problems, since we don't get to affect the overall lot of humankind—no matter which branch we ourselves take, there will be misery on some equally real branches and happiness on others, and we can do nothing about that.

To solve the probabilistic problems, people introduce the many-minds interpretation of the many-worlds interpretation. Each person has infinitely many minds. When we get to a branch point, each mind indeterministically "chooses" (i.e., is selected to) an outgoing branch according to the probabilities in the physics. Since there are infinitely many of these minds, at least in the case where there are finitely many branches coming out of a node we will expect each outgoing branch to get infinitely many of the minds going along it. So we're still splitting, and we still have the ethics problems since we don't get to affect the overall lot of humankind—or even of ourselves (no matter which branch we go on, infinitely many of our minds will be miserable and infinitely many will be happy).

But now I want to offer a traveling minds interpretation of the indeterministic theory. On the physical side, this interpretation is just like the many-worlds interpretation. It is a dualist interpretation like the many-minds one: we each have a non-physical mind. But there is only one mind per person, as per common sense, and minds never split. Moreover our minds are all stuck together: they always travel together. When we come to a branching point, the physical world splits just as on the many-worlds interpretation. But the minds now collectively travel together on one of the outgoing branches, with the probability of the minds taking a branch being given by the indeterministic theory.

In the diagram, the red lines indicate physical reality. So unlike in the original indeterministic theory, and like in the many worlds interpretation, all the branches are physically real. But the thick red lines and the filled-in nodes, indicate the observed branches, the ones with the minds. (Of course, if God exists, he observes all the branches, but here I am only talking of the embodied observers.) On the many-worlds interpretation, all the relevant branches were not only physically real, but also observed. Presumably, many of the unobserved branches have zombies: they have an underlying physical reality that is very much like the physical reality we observe, but there are no minds.

The traveling minds interpretation solves the probability problems. The minds can travel precisely according to the probabilities given by the physics. Traveling minds as generated in the above way will have exactly the same empirical predictions as the original indeterministic theory. (In particular, one can build traveling minds from a Copenhagen-style consciousness-causes-collapse interpretation of Quantum Mechanics, or a GRW-style interpretation.)

Traveling Minds helps a lot with the ethics problem that many-worlds and many-minds faced. For although physical reality is deterministically set, it is not set which part of physical reality is connected with the minds. We cannot affect what physical reality is like, but we can affect which part of physical reality we collectively experience. And that's all we need. Note that "we" here will include all the conscious animals as well: their minds are traveling as well. In fact, as a Thomist, I would be inclined to more generally make this a "traveling forms" theory. Thus the unselected branches not only have zombies, but they have physical arrangements like those of a tree, but it's not a tree but just an arrangement of fields or particles because it lacks metaphysical form. But in the following I won't assume this enhanced version of the theory.

Now while I don't endorse this theory or interpretation—I don't know if it can be made to fit with hylomorphic metaphysics—I do want to note that it opens an area of logical space that I think a lot of people haven't thought about.

Traveling minds is an epiphenomenalist theory (no mind-to-physics causation) with physical determinism, and is as compatible with the causal closure of the physical as any physicalist theory (it may be that physicalist theories themselves require a First Cause; if so, then so will the traveling minds theory). Nonetheless, it is a theory that allows for fairly robust alternate possibilities freedom. While you cannot affect what physical reality is like, you can affect what part of physical reality we collectively inhabit, and that's almost as good. We have a solution to the mind-to-world causation problem for dualism (not that I think it's an important problem metaphysically speaking).

I expect that I and other philosophers have incautiously said many things about things like epiphenomenalism, determinism and causal closure that the traveling minds theory provides a counterexample to. For instance, while traveling minds is a version of epiphenomenalism, it is largely untouched by the standard objections to epiphenomenalism. For instance, one of the major arguments against epiphenomenalism is that if minds make no causal difference, then I have no reason to think you have a mind, since your mind makes no impact on my observations. But this argument fails because it assumes incorrectly that the only way for your mind to make an impact on my observations is by affecting physical reality. But your mind can also make an impact on my observations by leaving physical reality unchanged, and simply affecting which part of physical reality we are all collectively hooked up to.

Epiphenomenalism and causal theories of content

According to causal theories of content, what makes my beliefs be about, say, horses is that the beliefs have the right causal connection with horses. Of course, there are going to be harder cases: I also have beliefs about unicorns, namely that they do no exist, and these beliefs do not have a causal connection with unicorns. But the unicorn beliefs get their intentionality derivatively from other thoughts, like those of animals and horns, from which they are constituted, derived, etc.

Now, beliefs about qualia are not constituted, derived, etc. from thoughts about non-qualia. So by causal theories of content, my beliefs about qualia have to have the right causal connections with qualia. So, causal theories of content are incompatible with epiphenomenalism, since according to epiphenomenalism qualia aren't causes.

Causal theories of content are the materialist's best bet for a theory of content. Qualia are meant to be a very modest addition to the materialist's story. But they aren't a modest addition—they require a revision of the theory of content.

Might I be a zombie?

According to epiphenomenalism, qualia—the raw experiential feels—are causally inert. In particular, it seems that my beliefs about qualia are not caused by the qualia, but by the neural correlates of the qualia. But this would lead to the absurd possibility that I might take myself to have exactly the sensory experience I now do—the visual experience as of a computer screen, the auditory experience as of keys tapping and fans running, the tactile experience as of my left leg tucked under me—while having no sensory experiences whatsoever. Moreover, it seems to open up the way for an odd sceptical hypothesis: maybe I am wrong in thinking I am conscious, but actually I am a total zombie!

Maybe the "I am a total zombie" hypothesis isn't an option. For maybe my occurrent beliefs are essentially conscious. Perhaps an occurrent belief is partly constituted by a content-providing neural state and the right as-of-believing quale. So without the qualia, I wouldn't have the beliefs, and in particular I wouldn't believe that I am conscious. So I couldn't be wrong in thinking occurrently I am conscious. Alright, so while the "I am a total zombie" hypothesis can be ruled out, the hypothesis that I am a partial zombie, that I have no sensory qualia but only the as-of-believing qualia, still around, and seems almost as problematic.

Maybe, though, the occurrent belief that I am having a visual experience as of a computer screen is partly constituted not by, or not just by, an as-of-believing quale, but by the qualia of the visual experience. If so, then I can't have the occurrent belief that I am having a visual experience while being a visual zombie.

If we take the above solution, though, we run the danger of violating the platitude that our beliefs cause our actions. For if my occurrent beliefs are partly constituted by qualia, and qualia are causally inefficacious, then it seems that it is not the beliefs but their causally efficacious neural constituents that cause the actions.

I am not sure how much weight to put on this objection to epiphenomenalism. After all, if my car's headlights blind a driver, then my car blinded the driver, even if only derivatively. There is no problem with overdetermination when one of the overdeterminers is derivative from the other. It is, perhaps, a little troubling that our occurrent beliefs only derivatively cause our actions, but that might in fact be just right. For it could be that an occurrent belief is partly constituted by a non-occurrent belief and something—maybe the as-of-believing quale—that makes it occurrent. And then it could be that the associated non-occurrent belief is what causes the action—after all, non-occurrent beliefs certainly do affect our actions.

So the "Might I be a zombie?" objection has fallen. But there is still an objection in the vicinity. My memory of having had experiences is not caused by these experiences. And that is wrong: a memory of A must be caused by A (at least in the derivative kind of way in which even absences are said to cause—I can, after all, remember an absence).