Mind-Body Physicalism (Part Four): Absent and Inverted Qualia

(Part One, Part Two, Part Three)

Right now I am looking at my laptop. To me it appears to be grey and black. Or at least, “grey” and “black” are the names I’ve come to associate with the colour experiences that I have when I look at it. Convention being what it is, you would probably associate the same names with your colour experiences of my laptop, but would our colour experiences really be the same? How do I know that your “black”-experience is not similar to my “green”-experiences?

These questions point us toward the problem of absent or inverted qualia. This problem forms the basis of an objection to mind-body physicalism that will be front and centre in today’s post. The post is part of a series on mind-body physicalism. And the series follows the material in William Jaworski’s Philosophy of Mind: a Comprehensive Introduction .


1. The Argument from Absent or Inverted Qualia
In the previous post, we discussed Frank Jackson’s famous knowledge argument against physicalism. This argument appealed to the private facts of experience (qualia), and their apparent separation from the subject matter of the physical sciences, in an effort to undermine physicalism. The argument from absent or inverted qualia does something similar. The argument itself looks like this:

• (1) If absent or inverted qualia are possible, then physicalism is false.

• (2) Absent or inverted qualia are possible.

• (3) Therefore, physicalism is false.

On the face of it, this is very simple stuff. But, of course, the devil is in the detail. We need to know exactly what absent or inverted qualia are and why they imply that physicalism is false; and we also need to know why absent or inverted qualia are possible. Let’s look at each of these issues in turn.

Inverted qualia are easily explained since they were alluded to in the intro. Qualia can be said to be inverted if different people have different qualitative experiences associated with the sensation of the same objects or states of affairs. As in your “black”-experience is equivalent to my “green”-experience. Absent qualia are slightly different. They can be explained by reference to the (infamous) philosophical concept of zombies. These are beings who are externally identical to us - i.e. they walk the same walk, and talk the same talk - but who completely lack the qualitative experiences we associate with activities such as walking and talking (note: there’s nothing special about these activities; I chose them for illustrative purposes only).

Why would either of these phenomena pose of problem for physicalism? Well, if physicalism is true, then qualia would have to be either (i) physical states of some sort or (ii) non-existent. Since we all appear (from our own perspective) to be having qualitative experiences, (ii) would seem like a non-starter. So qualia must be physical states. But if they are physical states, then their presence should be determinable by identifying physical states such as patterns of brain activation. This is where absent or inverted qualia become important. If such things are possible, then the same physical states can either (a) be associated with different qualitative experiences or (b) be associated with no qualitative experiences at all. But this can’t be right if qualia are identical to physical states. So the possibility of inverted or absent qualia would indeed imply the falsity of physicalism. Let’s phrase this in the form of an argument:

• (4) If physicalism is true, then qualitative states (qualia) must identical to specific physical states.

• (5) If absent or inverted qualia are possible, then the same physical state can be associated with completely different qualitative states.

• (3) Therefore, if absent or inverted qualia are possible, physicalism is false.

Finally, let’s move on to consider why absent or inverted qualia are possible. Again, if you’ve been following this series closely, it should come as no surprise to learn that a conceivability-possibility principle is doing all the work here. Proponents of the argument will say that since zombies and inverted qualia are conceivable (you just conceived of them as you were reading this, right?), they are also metaphysically possible. Hence, premise (2) of the argument is justified.


2. Responding to the Argument
In Chapter 4, Jaworski doesn’t go into the various responses to this argument in any great depth. This is mainly because he addresses them elsewhere in the book. His discussion of this argument is among the first stops on a very long trek through all the different physicalist theories. Still, a few words can be said about possible responses.

First, the argument relies on the dubious conceivability-possibility principle. We discussed the problems with this when looking at substance dualism. I advise the interested reader to read back over that discussion. In any event, even if the principle is sound, it is open to the physicalist to object to the true conceivability of absent or inverted qualia. They could say that the relevantly similar physical states must, necessarily, be associated with the same qualitative states. In doing so, they can challenge the proponent of the argument to come up with a clear and distinct conception of both phenomena.

Second, physicalists can reject the reality of qualia. As counterintuitive as it seems, several have taken this route. Daniel Dennett is probably the most well-known exponent of this view, but Wittgenstein’s private language argument has similar implications. Jaworski discusses both in chapter 8. To make this series somewhat self-contained, I’ll present Dennett’s argument now (I won’t evaluate it though).

Qualia are typically defined as properties that are (a) intrinsic/non-relational and (b) directly knowable. They are non-relational in that they do not play a part in the kinds of causal relations analysed by physicalists; and they are directly knowable in the sense that they are known non-inferentially from the first-person perspective. Dennett denies that qualia can be both of these things at the same time. His argument starts by assuming that proponents of qualia think that qualia play some role in our behaviour and then deduces from this the fact that qualia cannot exist. It looks like this:

• (6) Exponents of qualia must claim either (i) that qualia influence behaviour in conjunction with our beliefs, desires and other propositional attitudes; or (ii) that qualia influence behaviour independently of propositional attitudes.

• (7) If qualia affect behaviour independently of our propositional attitudes, then qualia cannot be non-relational.

• (8) If qualia affect our behaviour in conjunction with our propositional attitudes, then qualia cannot be directly knowable.

• (9) Therefore, qualia cannot be both non-relational and only directly knowable.

Premise (6) might seem a little odd, but it makes sense. Speech acts such as verbal reports are a kind of behaviour. So if speech acts like “I see a blue ball” or “I see a red ball” are linked with qualitative experiences — as proponents of qualia would have us believe — then those experiences must exert some influence on our behaviour.

Premise (7) is supported by the idea that if qualia directly influence behaviour, then they must do so by playing a direct causal role in behaviour, i.e. < Red quale → “I see red” >. So they would have to be defined in relational, as opposed to non-relational terms.

Premise (8) is a little trickier. The idea is that if qualia only influence behaviour when they are conjoined to other beliefs and desires, then one cannot know one’s qualia without knowing those other beliefs and desires. In other words, qualia can only be known when the surrounding circumstances are known. Dennett supports this idea with a few thought experiments. Here’s one:

• (10) Mad Scientist : A mad scientist has manipulated your brain while you were asleep. When you wake up, you declare that your sensory experiences are qualitatively different from the way they were before. But how can you know this? It could be that the mad scientist succeeded in altering your qualitative experiences, or it could be that he altered your memories. Either is possible if it is “qualia + beliefs” that influence behaviour. One can only tell the difference by knowing something about one’s memories and/or the brain states manipulated by the mad scientist.

This probably seems a little strange. It does to me, at any rate. But Dennett argue that denying the existence of qualia need not be as counterintuitive as it first appears. He reckons that a third-person conception of mental phenomena can accommodate most of the facts cited in support of qualia. He does so partly on the grounds that many phenomena that are thought to be non-relational turn out, on closer inspection, to be relational.

Like I said, I won’t evaluate this here but one obvious objection should be noted. The first premise of Dennett’s argument (premise 6 above) assumes that qualia influence behaviour. There is at least one school of thought — epiphenomenalism — that would deny this.

Okay, well that’s it for this series. As I said at the outset, unlike Jaworski’s book, this has been far from a comprehensive assessment of the arguments for and against physicalism. It was only intended to introduce some of the evidence cited in support of physicalism (argument from past explanatory success) and some of the classic objections to the physicalist worldview (Hempel’s dilemma, The Knowledge Argument, and the problem of absent or inverted qualia).

Mind-Body Physicalism (Part Three): The Knowledge Argument

(Part One, Part Two)

The travails of Mary, the brilliant vision scientist confined to work in a black and white lab, have been a staple in the philosophy of mind ever since they were first-described in a thought experiment by Frank Jackson. They’ll be featuring heavily in today’s post as well, which is part of my ongoing series on mind-body physicalism. As noted in previous entries, the series follows the discussion in William Jaworski’s Philosophy of Mind: a Comprehensive Introduction .

Jackson’s thought experiment is used to set-up something called the knowledge argument. The purpose of this argument is to illustrate the explanatory incompleteness of physicalism. If the argument is successful, there are grounds for dismissing physicalism; if it is not, then physicalism can live to fight another day. Thus, the defender of physicalism would be wise to address the argument.

In this post, we'll discuss the thought experiment, the argument, and the various responses. And we'll do so in that order.


1. What Mary doesn’t Know
Let’s get better acquainted with our fictional Mary first. She’s a brilliant vision scientist. If you have any questions about the nature of human vision, you should talk to her. She knows every physical thing there is to know about human vision: she knows about the anatomy of the brain; she knows about the electrical and chemical responses associated with vision; she knows about the electromagnetic properties of different objects; and she knows which electromagnetic properties are associated with which physiological responses in the brain.

But here’s the thing. For some reason, Mary has spent her whole life in a black-and-white environment. The walls of her lab are painted black; all her lab equipment is white; her clothes are black; she wears black and white gloves; and her skin is painted white. As a result, she’s never actually had the experience of colours such as red or yellow. So although she could tell you all about the electromagnetic properties of red objects, and the brain states associated with the sight of red objects, she hasn’t seen any red objects for herself.

Now suppose that one day she manages to break free from her black-and-white lab, and go on a trip to the local market. While there, one of the vendors tries to sell her a tomato. She looks at this strange object for the first time, contemplating what she sees.

Question: does Mary acquire any new knowledge by looking at the red object?

2. The Knowledge Argument
To most people, the answer to that question is “yes”. By seeing a red tomato for the first time, Mary learns that the colour red is associated with a unique qualitative experience, one that she has not had before. Thus, although she knows everything about the physical nature of vision, she knows something more now: she knows what it is like to experience the colour red.

This intuitively appealing answer creates a problem for the physicalist. The problem can be expressed in the form of the following argument:

• (1) If physicalism is true, then all facts are physical facts.
• (2) If it is possible for someone to know all the physical facts without knowing all the facts, then not all the facts are physical facts.
• (3) If it is conceivable that someone can know all the physical facts without knowing all the facts, then it is possible for someone to know all the physical facts without knowing all the facts.
• (4) It is conceivable that someone can know all the physical facts without knowing all the facts.
• (5) Therefore, it is possible for someone to know all the physical facts without knowing all the facts (from 3 and 4).
• (6) Therefore, not all the facts are physical facts (from 2 and 5).
• (7) Therefore, physicalism is false (from 1 and 6).

Let’s talk about the support for this argument first. Premise (1) seems to be an accurate statement of the physicalist thesis. Premise (2) depends on the following train of thought: if one knows all the physical facts but does not know all the facts, then there must be a fact (call it “q”) that one does not know. If q were a physical fact, then one would know it. So q must be a non-physical fact. But in that case it follows that if it is possible to know all the physical facts and not know q, then not all facts are physical facts. Phew! Read through that again if you need to.

Moving on, premise (3) incorporates a conceivability-possibility principle. This allows us to say that the conceivable is possible. We discussed such a principle before in relation to substance dualism. Now would be a good time to check back over that discussion. Finally, premise (4) is supported by the Mary thought experiment. The thought experiment has three key elements to it:

• (8) The Mary Thought Experiment The following scenario is conceivable: (i) Mary knows all the physical facts; (ii) Mary has never experienced colour; and (iii) Mary learns a new fact upon experiencing colour for the first time. Since no one can learn something that they already know, it would seem to follow that (4) is true.

3. Responding to the Argument
How then can the physicalist respond? Well, premises (1) and (2) would seem rather unobjectionable. Premise (3) is definitely objectionable, but the possible objections were already covered when looking at substance dualism. That leaves premise (8) (which supports (4)). Jaworski says that the physicalist can object to the conceivability of either one of the three elements of the thought experiment, or some conjunction of the three elements. Let’s look at how this might play out in practice.

One could argue that it is impossible to have complete knowledge of the physical facts (contrary to (i) above). This could be due to some inherent limitation of the human sciences. Thus, although science progresses in incremental steps, and improves with most of those steps, it never quite obtains perfect knowledge. Instead, the knowledge curve is asymptotic. This model of scientific knowledge is compatible with Popper’s fallibilism.

Alternatively, one could argue that the conjunction of (i) and (ii) is inconceivable. In other words, one could argue that someone cannot know certain physical facts unless one has had experiences of colour. I’m not exactly sure how that argument would run but it has some prima facie plausibility.

The conjunction of (i) and (iii) can be challenged in a variety of ways. Some critics challenge the idea that one learns a new physical fact when one has colour experiences. They say that, instead, one learns how to see the same set of physical facts under a different description or representation. To be precise, they say that one shifts to a first-person representation from a third-person one. So the facts remain the same, all that changes is how they are represented. That’s a little esoteric, so another way to challenge (i) and (iii) is to argue that physical facts logically entail facts about conscious experience. Thus, anyone who knew all the physical facts would be able to deduce facts about conscious experience. It’s been a long time since I read it, but I seem to recall Daniel Dennett offering this up as a possibility in Consciousness Explained (of course, he objects to the standard understanding of qualia as well).

There is a third way in which to challenge (i) and (iii). It is to adopt the ability hypothesis. According to this hypothesis, there is a distinction to be drawn between two types of knowing: (a) knowing-how and (b) knowing-that. The former involves knowledge of abilities and skills; the latter involves knowledge of facts. Applied here, the distinction allows us to say that when Mary experiences the colour red for the first time, she does not learn a new fact; instead, she learns a new skill.

Here’s a list of all these objections to premise (8):

• (9) It is inconceivable that anyone could have complete knowledge of all the physical facts.
• (10) It is inconceivable that one could know all the physical facts without having had conscious experiences of colour.
• (11) Mary does not learn any new facts when she has a conscious experience, instead she represents the same facts in a different way.
• (12) Anyone who knew all the physical facts would be able to deduce facts about conscious experience from them.
• (13) Mary does not learn a new fact when she has a conscious experience, instead she learns a new skill.

Do any of these responses work? Very hard to say. As Jaworski notes, both the knowledge argument and the responses to it remain highly controversial.

Mind-Body Physicalism (Part Two): Hempel's Dilemma

(Part one)

This post is the second in a brief series on the basic arguments for and against mind-body physicalism. The series follows the discussion in William Jaworski’s book Philosophy of Mind: a Comprehensive Introduction . This post is subject to all the caveats and qualifications mentioned in the first post.

To recap a little, the mind-body physicalist is, at the most abstract level, committed to the view that mental reality is ultimately identical to, supervenient upon, or realized by the entities posited in fundamental physics. As we saw the last day, one argument for this thesis is the argument from past explanatory success: physicalist explanations have been successful in the past so they are likely to be successful in the future. In today’s post we’re going to consider a classic objection to physicalism: Hempel’s dilemma. This is, in fact, a specific instance of a broader problem in the philosophy of science and so has ramifications that extend beyond the mind-body problem.

Let’s see what all the fuss is about.


1. Hempel’s Dilemma
For the purposes of this presentation, I am going to reach beyond the confines of Jaworski’s book and look instead to (part of) the discussion of Hempel’s dilemma in Andrew Melnyk’s book A Physicalist Manifesto . I do so because - solid and all as Jaworski’s presentation is - Melnyk is slightly clearer about both the constraints facing the physicalist that give rise to the dilemma, as well as the subsequent implications of the dilemma. Indeed, Melnyk has a gift for clarity, rigour (and, indeed, humility) that is on display throughout his book. This gift makes his probably the best overall defence of physicalism on the market.

Anyway, Melnyk notes at the outset of his book that a physicalist need not perform any sort of conceptual analysis on the term “physical”. This is because the physicalist’s goal is not necessarily to closely track ordinary language or meaning, but instead to provide content to a thesis. Thus, it is open to the physicalist to provide an entirely stipulative definition of the “physical” and work from there. Still, even that stipulative definition will be subject to some constraints. He lists three:

(i) It cannot be obviously false : This seems like a straightforward constraint. Anyone who commits themselves to a thesis cannot also be committed to its falsity, can they?

(ii) It cannot be analytic or trivial : This seems legitimate. For example, if physicalism were simply defined as the thesis that “whatever exists is physical” it would be trivially true. It would have no possibility of being false and would say nothing interesting about the fundamental nature of reality (including mental reality).

(iii) It must have some content that is determinable now by us: This, also, seems legitimate. We cannot, it would seem, accept a theory that is devoid of currently determinable content because such a theory would have two unwelcome implications. First, it would not automatically exclude many things that we now take to be non-physical. And second, it would prevent us from taking currently available scientific evidence as evidence for or against physicalism.

Although each of these constraints is plausible, they create a bit of a problem for the physicalist. The problem is that it is impossible for an adequate definition of physicalism to satisfy both (i) and (iii) at the same time. This can be expressed in the form of an argument, as follows:

• (1) If “physicalism” is to be an adequate theory, it’s definition must satisfy three conditions: (i) it must not be false; (ii) it must not be trivial and (iii) it must have content that is determinable now by us.

• (2) “Physicalism” can either be defined by reference to the current content of physical theories or to the content of some future ideal physical theory.

• (3) If “physicalism” is defined by reference to current physical theories, then conditions (ii) and (iii) are met but (i) is not.

• (4) If “physicalism” is defined by reference to a future ideal physics, then conditions (i) and (ii) are met but (iii) is not.

• (5) Therefore, physicalism is not an adequate theory.

Now you may be wondering: what reason do we have to accept (3) and (4)? The answer is the following. We have reason to accept (3) because past experience suggests that physical theories are constantly being refined, replaced and superseded by better physical theories. So if past experience is any guide - and who are we to assume otherwise? - the content of current physical theories is almost certainly false. We have reason to accept (4) on the grounds that a future ideal physics must, necessarily, have content that is not now determinable by us, otherwise we would already be in possession of the ideal theory.

The argument contains within in it a dilemma, usually attributed to Carl Hempel: either the physicalist accepts a theory that is almost certainly false; or he accepts a theory that has no content; he can’t do both.



2. Responding to the Dilemma
I’ll switch back to Jaworski’s book now. He notes that, as with all dilemmas of this sort, there are various strategies open to the physicalist in response. They can grasp one or other of the horns and say that the implications are not as dire as they first appear; or they can deny one of the premises that gives rise to the dilemma, thereby slipping between its horns. Jaworski notes that the second strategy is - perhaps surprisingly - not all that popular (although Melnyk could actually be interpreted as opting for that approach). Instead, most defenders of physicalism have grasped one of the horns.

For instance, there are those who say that accepting a theory, even though it is likely to be proved false in the future, is not that big a deal (again, Melnyk could be interpreted as taking this approach). They take their inspiration from the fact that this is simply par for the course in physics. One defends whatever theory seems most likely to be true at a particular moment in time. This is how we progress toward better theories. There’s no real problem here.

• (6) There is no real problem associated with accepting a theory that is probably false: this follows best scientific practice.

Alternatively, there are those who accept that physicalism must be defined relative to an ideal physics. They tend to deny that a commitment to physicalism in the here and now lacks content. They’ll say current physics provides some clue as to the content of future physics. They justify this claim by pointing out that although physical theories have been refined and replaced over the past 400 years or so, the older theories are rarely deemed to be completely false. Some of the content from those theories carries over. Thus, even if physics hasn’t bottomed-out at the fundamental level of reality yet, we know enough now to say that mental entities will not exist at that fundamental level. They will, instead, be made up of components from that level.

• (7) Defining physicalism relative to an ideal future theory does not render it devoid of content.

As I see it, both (6) and (7) function as denials of (1). That is, they supply reason for thinking that a theory which fails to meet those three conditions can still be adequate. This is reflected in the diagram below.

Okay that’s it for now. In the next post we’ll consider the famous knowledge argument against physicalism.

Mind-Body Physicalism (Part One): The Argument from Past Explanatory Success

Since I did a whole series on the basic arguments for and against substance dualism, I thought it might be nice to do a symmetrical series on the basic arguments for and against mind-body physicalism. I’m sure some of my readers will like this too - they suggested as much in the comments section. As with my series on substance dualism, William Jaworski’s book Philosophy of Mind: a Comprehensive Introduction will be the source material.

It’s only right that I warn you at the outset: Although the motivation for this series is to serve the interests of symmetry, there are differences between the treatment of the two positions that will make this series on physicalism far less satisfactory than the one on substance dualism. Primarily, this is due to the fact that there has been a lot more theoretical refinement of physicalism over recent years. Indeed, such is the volume of theoretical refinements that Jaworski spends four whole chapters going over them.

I don’t wish to follow each and every refinement here - there’s no sense in producing the book as a whole - so instead I’ll just cover one basic argument for physicalism (the argument from past scientific success) and three objections to physicalism (Hempel’s dilemma, the knowledge argument, and the problem of inverted qualia). These three objections provide the springboard for the further refinements mentioned above. Some of these are impressive and the arguments in their favour can be quite compelling, but if you’re interested in these then I recommend getting a hold of Jaworski’s book (this is the last recommendation for a while - I don’t want to end up as Jaworski’s personal promoter).


1. The Argument from Past Explanatory Success
Physicalists come in many flavours, but they usually share one basic commitment: the commitment to the fundamentality of the physical sciences. That is to say, they all tend to believe that whatever reality ultimately consists in will only be properly described using the language of physics. Furthermore, that which is properly described using the language of physics is called “physical”. So since the mind is part of reality, it would seem to follow that mind must ultimately be physical.

Clearly this commitment to physics is in want of justification. This is where the argument from past explanatory success comes into play. Before discussing that argument it’s worth making something clear: there are other arguments in favour of physicalism in general and also in favour of particular forms of physicalism. Indeed, we encountered one such argument - the argument from the problem of interaction - when looking at substance dualism. But even that argument would seem to trace its authority back to the explanatory success of physics. Anyway, the argument itself takes the following form:

• (1) If explanations of type A have, in the past, been superior to explanations of type B (with respect to a broad range of subject matters), then explanations of type A are likely to be superior to explanations of type B with respect to other subject matters.

• (2) Physical explanations have, in the past, been superior to non-physical explanations with respect to a broad range of subject matters.

• (3) Mind-body relations are a subject matter in want of an explanation.

• (4) Therefore, physical explanations are likely to be superior to non-physical explanations with respect to mind-body relations.

Now this might look a little bit strange. For one thing, it doesn’t appear in this form in Jaworski’s text. He presents the argument as a straightforward {“Physical explanations have been superior to non-physical explanations in the past” → “Therefore, physical explanations are likely to best with respect to mind-body relations”} inference. His version makes the inductive gap between the premise and the conclusion transparent. I’ve tried to plug this gap by introducing an explicit inductive principle in the shape of premise (1). But this does not change the overall strength of the argument.

And this is the critical point. Inductive arguments of this sort cannot provide decisive reasons in favour of a particular conclusion. They can only provide probabilistic reasons for supporting a conclusion. The probabilities in question might be very high, but they are probabilistic nonetheless. Does this make things easier for the critic of physicalism? Not necessarily. We each of us rely on inductive principles, so the proponent of an alternative theory should be reluctant to dismiss the argument solely because it is inductive in nature. Instead, they should prefer to provide some good reason for thinking induction is unwarranted in this particular instance. Which brings us to….


2. Supporting the Argument
The key to the argument from past explanatory success is the support given to premise (2). If many impressive examples of successful physical explanations can be given, then dualists will have their work cut out. To block the induction from these case studies, they will need to show that mind-body relations are completely disanalogous to them. That’s certainly not impossible but it must be done nonetheless.

So what examples can be adduced in support of premise (2)? Jaworski offers four. Now, I’m not a historian of science so I can’t really vouch for the accuracy of each of them. They sound plausible to me but, for instance, I have no idea if people ever really did explain magnetism by appeal to non-physical spirits. Also, I would presume that the success of physicalistic explanations in each of these domains is determined by following the rules of inference to best explanation or some probabilistic alternative (Bayesian or Likelihoodist). In other words, physicalist explanations win against competitor explanations because they are simpler, afford us greater predictive and manipulative powers, confer a higher probability on the data and so on ( see this series for more ).

Anyway, the four examples are:

• (2.1) Magnetism : At one point in time people tried to explain magnetic by positing the presence of nonphysical spirits in magnetised objects. A physicalistic explanation of magnetism in terms of the electromagnetic force proved far more successful.

• (2.2) Planetary Motion : At one point people thought non-physical intelligences (gods) could account for the orbital movements of the planets. This was replaced by a far more successful physicalistic explanation of those movements by reference (initially) to Newtonian laws of gravity and (eventually) to the warping of spacetime.

• (2.3) Life : People once thought that the only thing capable of explaining the nature and behaviour of living things was by positing the existence, in them, of non-physical vital spirits. This has now been replaced by a far more successful explanation of life in terms of mechanical metabolic and reproductive processes.

• (2.4) Mental Illness Abnormal human behaviour was once explained by reference to possession by non-physical beings. Now many (if not all) such abnormalities can be explained by reference to tissue pathologies or alterations in the electrical and chemical balance of the brain.

We can plug these four examples into the argument and then map it out as follows.

Now as has been stressed already this argument is far from watertight. We’ll consider the various problems with it, and with physicalism as a whole, over the remainder of this series.