consciousness

Mary the Qualia-Blind Neuroscientist

Nick Alonso

A famous philosophical thought experiment imagines Mary, a neuroscientist, who knows all the physical, biological, and functional facts about the human color vision system. Crucially, Mary has never had a conscious experience of color until some point after she acquires all of this neuroscientific knowledge. This raises a question: when Mary consciously experiences color for the first time, does she learn something new about color experience? The thought experiment is meant to support Dualism, the view that consciousness is non-physical in some way.

The purpose of this blog, however, is not to discuss this well-trod debate about Mary and Dualism. Instead, below, I imagine a variant of the Mary thought experiment that is meant to support Illusionism.

What is Illusionism? ‘Phenomenal realists’ say consciousness has a ‘what-it-is-likeness’, ‘phenomenality’, ‘phenomenal character’, or ‘subjective character’ (henceforth, just phenomenal character). What it is like to experience the color red from the first person point of view, for example, is the phenomenal character of the red experience. Realists say explaining how and why consciousness with phenomenal character arises from the brain is a very hard problem, maybe the hardest in all of science. Illusionists, on the other hand, accept that it surely seems as if this phenomenal character exists but deny it actuality does, and, if there is no phenomenal character, there is no hard problem.

Most find Illusionism to be highly implausible. The argument I present below is meant to make Illusionism more palatable. The argument uses a hypothetical scenario to present a kind of dilemma for phenomenal realists — it seems to force phenomenal realists to accept one of two difficult to defend conclusions. I am still unsure how challenging this dilemma is for Realists, but I am convinced it is non-trivial. In any case, the hypothetical scenario is an interesting one to think through.

I have not found previous work that discusses a scenario exactly like one I describe below, though a few years ago Eric Thomas presented a similar thought experiment. Thomas imagines a non-conscious alien scientist studying cats. His thought experiment begins with phenomenal Realist assumptions and uses the thought experiment to present an argument for Dualism. The thought experiment I present below, on the other hand, imagines a non-conscious scientist studying humans. My argument begins agnostically about the Realist-Illusionist debate and is used to present an argument for Illusionism.

The Non-Conscious Neuroscientist Scenario

Imagine a neuroscientist, Mary, who is non-human. We can, for example, imagine she is an alien or AI. Despite being non-human, Mary is highly intelligent and cognitively similar to humans in most ways except for one: unlike humans, Mary does not have phenomenal experience herself nor does she have any intuition that she has mental states with phenomenal character.

Mary has an intuitive psychology not unlike humans’, which disposes her to represent her own and others’ minds as consisting of states similar to what we call beliefs, desires, perceptions, intentions, etc. However, she understands these states in a way that is independent of any relations to phenomenal character. She may, for example, understand them purely in terms of their functional aspects, i.e, their causal relations to each other and behavior, but Mary has no intuitive sense these mental states have any special phenomenal character.

In addition to an intuitive psychology, Mary has extensively studied her own brain and human brains, so much so that she has a complete knowledge of all the physical-functional facts about her own and human brains. She knows all the facts about their physical-biological properties from the cellular level down to the level of atoms. She knows all of their computational-functional properties, from abstract cognitive levels down to fine-grained neural levels.

This knowledge, of course, includes a complete physical-functional understanding of why humans tend to say they have mental states with a mysterious phenomenal character. (For simplicity, I’ll call verbal reports about one’s own mental states with phenomenal character ‘p-reports‘.) Mary knows all the cognitive-computational mechanisms that dispose humans to make p-reports and she knows how these cognitive processes are implemented in the human brain. Mary has even identified the particular cognitive-computational states and processes that seem to be at the root of the human tendency to generate p-reports, i.e., the main source(s) of human p-reports.

What Should Mary Believe about Consciousness?

The first question to consider is what should Mary believe (emphasis on ‘should’) about the nature of, what people call, phenomenal consciousness? In particular, should she believe people have mental states with phenomenal character or not?

Assume Mary begins agnostically. She initially assigns equal probability to both Realism and Illusionism. She should now only adjust her credences appropriately in response to relevant rational argument and empirical data.

So, what arguments and data might there be for Mary to increase her credence in Realism?

The first point to make is that just because people insist they have experiences with phenomenal character is not evidence that they actually do. People’s p-reports are empirical data that are equally as consistent with Illusionism as they are with Realism. Illusionism, like Realism, predicts people should say they have conscious experience with mysterious phenomenal character and write books about these mysterious properties of consciousness, and so on. In order for p-reports to be evidence against Illusionism, they would have to be more probable under Realism than Illusionism, but they are not.

Consider a related point: Mary has a complete consciousness-neutral, physical-functional description of the causes of p-reports that does not assume anything philosophically mysterious like phenomenal character exists. This description will sufficiently explain why humans tend to generate p-reports in the sense the p-report generating processes it describes will entail that such behaviors should come about, just as any human behavior is entailed by some prior physical-functional state of the brain and body. Therefore, phenomenal character is not needed to provide a sufficient causal explanation of p-reports in this sense, and cannot in this sense provide Mary with reason to believe phenomenal character exists.

The second point to make is that Mary’s knowledge of the human brain does not appear to provide reason for her to increase her credence in Realism. To see this, consider the possibility that the explanatory gap exists. The explanatory gap is the view that physical-functional facts about the brain do not entail anything in particular about phenomenal character. For example, it does not seem that certain physical-functional states of the visual cortex, say, should entail the existence of a color experience with particular phenomenal character rather than some other experience or no experience at all. Many philosophers believe this gap exists.

If we assume this gap exists, from Mary’s point of view, there would be nothing in particular about phenomenal character, including the probability that it exists, that is implied from her complete physical-functional knowledge of the human brain. If the explanatory gap exists, any physical-functional facts about the brain cannot provide Mary with reason to increase her credence in Realism.

Next, consider the case where the explanatory gap does not exist — physical-functional facts about the brain do entail facts about the phenomenal character of experience. In this case, one might think Mary would have reason to favor Realism: if certain physical-functional facts about the brain entail certain conscious states with certain phenomenal character should exist, and Mary understands these entailments, she would realize phenomenal character must exist.

However, it is hard to make sense of this idea. How could Mary even understand/conceptualize phenomenal character in the same way humans do? First, unlike humans, she cannot understand phenomenal character introspectively, since she has no experience herself. Mary, therefore, cannot understand phenomenal character under the common description “what it is like to have some experience from the first-person point of view”. Second, phenomenal character would not be mysterious to her. If certain physical-functional facts entailed that certain conscious states with certain phenomenal character exists, and Mary knows and understands the details of these entailments, she should not get the feeling there is anything mysterious or deeply problematic about phenomenal character. She would not understand phenomenal character as “that aspect of consciousness that is deeply hard to explain in third-person, physical-functional terms” because no aspect of consciousness would be deeply problematic to explain in physical-functional terms from her third-person point of view.

Any concept of consciousness and phenomenal character cognizable by Mary, that she could deduce from her knowledge of the human brain, would seem to be a deflated version of the conception used by human phenomenal realists, in these ways. Instead, Mary’s resulting deflating concept of phenomenal character would seem to perfectly consistent with the concepts of consciousness used by Illusionists, who define consciousness in some physical-functional way without reference to any introspectable, mysterious properties.

Thus, in any case, whether there is or is not an explanatory gap, physical-functional facts about the brain do not seem to provide Mary reason to believe mental states with phenomenal character (in the realist sense) exist.

(Note also there is a third possible scenario, where there is no explanatory gap but Mary does not understand the entailments between physical-functional brain facts and phenomenal character. In this case, Mary would face the same challenge as the case where there is an explanatory gap — she would not know that or how physical-functional facts about the brain entail facts about consciousness with certain phenomenal character and, therefore, these entailments would not provide her with reason to believe any phenomenal character exists.)

So, empirical knowledge about human verbal reports and the physical-functional properties of the human brain do not provide Mary with reason to increase her credence in Realism. If data about human behavior and the brain cannot do so, what can? The remaining possibility is a priori philosophical arguments against Illusionism.

The challenge with this approach is that in order for such arguments to provide reason for Mary to update her beliefs, they cannot assume introspective access to consciousness. For example, unlike people, Mary cannot by swayed by the common argument ‘I know conscious states with a mysterious phenomenal character exists because I observe they exist in my own mind‘ or ‘If I know anything it is that I am having certain experiences right now with certain phenomenal character‘. Mary has no such introspective access to conscious experience with phenomenal character, so such arguments should not persuade Mary. Furthermore, Mary should not be swayed by arguments that appeal to common sense since it is not common sense to Mary (or any other intelligences like Mary) that phenomenal character exists.

What philosophical arguments could phenomenal realists appeal to that do not assume introspective access to phenomenal consciousness? It is unclear at best what these would be. It is far outside the scope of this blog to survey all of the various criticisms of Illusionism here one by one, but I think the main challenge for Realists is that many, if not most, of the prominent criticisms of Illusionism appeal to introspection in some way. If an argument requires an introspective understanding of consciousness, should be ineffective at swaying Mary who has no introspective understanding of phenomenal consciousness.

For example, one approach, taken by Eric Schwitzgebel is to try to define phenomenal consciousness in an “innocent” way that does not explicitly refer to phenomenal character or other mysterious properties. Instead, it just defines consciousness by whatever property is shared by the mental states people call conscious states. By removing the reference to phenomenal character in the definition, Illusionist views that make direct claims about phenomenal character can be avoided.

The issue here is the shared property that Schwitzgebel seems to have in mind is one that is identified upon introspection. Phenomenal consciousness, under his definition, “is the most folk psychologically obvious thing or feature that the positive examples possess and that the negative examples lack”. Such a folk-psychological definition would therefore necessarily not involve knowledge learned by scientifically studying the physical-functional facts about brain. Instead, this folk-psychological definition would rely on feature(s) identified in the intuitive common fashion, i.e., via introspection.

However, under such a definition, Mary cannot understand what humans are referring to by introspecting her own mind, since she does not introspect anything she is disposed to call phenomenal conscious states. Mary’s only way to try to identify what humans are referring to would be to study human judgments/verbal reports about consciousness and develop a scientific theory of what it is they are referring to when introspecting and reporting about phenomenal states. For example, if there is some physical-functional state of the brain (e.g., a source of p-reports) that tracks these judgments well, she could use this to develop a scientific, third-person description of what people are referring to when they claim to be introspecting phenomenal character.

However, Mary’s resulting concept of phenomenal consciousness would seem to be consistent with Illusionism. Whatever physical-functional properties Mary identifies would not be deeply mysterious — they would not resist objective, physical-functional explanation from Mary’s point of view since they are themselves physical-functional properties.

This seems to leave us in the same position as before: whatever Mary can try to identify with what people call phenomenal states would seem to be something that leads to a deflated, non-mysterious concept of consciousness totally consistent with Illusionism. Her understanding of consciousness would not lead her to believe there is a hard problem of consciousness. It would not lead her to think consciousness is any different than any other cognitive process.

While there are other anti-Illusionist arguments, I suspect most will somehow require an introspective understanding of consciousness, through some introspective reference to ‘this’ or ‘that’ aspect of consciousness. Since Mary cannot understand such properties introspectively, she can only try to understand them from the outside by trying to explain the associated human verbal reports by their neural-cognitive causes. She can always develop some physical-functional explanation for the reports, but such an explanation will not describe anything that is mysterious, that resists objective, physical-functional explanation. Whatever understanding/descriptions Mary ends up with will leave her with little reason to believe in human mental states with some mysterious phenomenal character.

Another issue for Realists is that there exists a priori philosophical arguments in favor of Illusionism that do not depend on any introspection at all, such as Chalmers’ evolutionary debunking arguments and simplicity arguments in favor of Illusionism. Debunking arguments argue that there is an evolutionary explanation of why humans tend to make p-reports that does not assume they are true, and thus if they are true there would be some epistemic luck, which is implausible. Therefore, the best conclusion is p-reports are false. Simplicity arguments point out Illusionism is simpler than Realism in that it assumes fewer entities exist than Realism does, and Illusionism does not need to assume anything else exists to causally explain all observable physical-functional facts (due to causal closure of the physical universe). In this sense, Illusionism should be preferred.

Importantly, neither of these arguments make any references to introspection. Chalmers’ debunking arguments only make claims about human behavioral dispositions, evolution, and beliefs. Simplicity arguments only makes a simple point about the number of entities each theory claims exist and the causal closure of physics.

Mary’s cognitive set-up, that of having no phenomenal states, seems to remove the force from many common anti-Illusionist arguments, but it does not seem to remove any force from pro-illusionist arguments. This suggests that a priori philosophical arguments should, at least, not alter Mary’s credences, and possibly even sway Mary’s credences in favor of Illusionism.

Mary’s Dilemma for Realism

Now, we come to the second question: why should we, humans, conclude anything different than Mary?

As far as I can see, Realists have two options:

Option 1: They can disagree with the points made in the last section and argue Mary should not conclude Illusionism is at least as plausible as Realism. Instead, Mary should conclude Realism is more plausible. For the reasons previously mentioned, this argument seems challenging.

Option 2: Realists can argue that while Mary should conclude Illusionism is at least as plausible as Realism, humans should conclude Realism is more plausible than Illusionism. Taking this line of reasoning would accept that Mary’s reasoning is valid, but it would argue Mary lacks certain justification that humans have for believing Realism. A challenging question for those taking this option is the question of what this justification is?

There are a few ways Realists might try to answer this question. A simple answer for the Realist would take a Dualist approach and say Mary lacks knowledge of non-physical properties of consciousness. Mary’s mind has no such properties so she cannot access them introspectively, nor can she gain knowledge of them by studying the physical brain. Human minds to have non-physical properties which they can access upon introspection, and therefore humans have some knowledge/justification for believing phenomenal Realism that Mary lacks. The problem with this Dualist approach, is that just about every scientist and philosopher would want to avoid such views, given all the well-known problems that come with Dualism.

Another possible response from Realists would be to simply stipulate people have some special, certain knowledge of phenomenal character gained through introspection of their conscious states (whether they are physically reducible or not). However, Illusionists, like Dan Dennett and Keith Frankish, have pointed out now for decades that such views lack good explanation. If an individual claims some special introspective knowledge or justification for their belief in phenomenal states, through statements like “I have privileged, certain knowledge of my own experiences and their phenomenal characters”, they have to define and explain the concepts they use, such as what the “I” is, what the “phenomenal character” is, and how the special knowledge relation between the two works.

Some philosophers like Chalmers have tried to make direct responses to challenges like this one from Illusionists. However, they make controversial assumptions. For example, here’s part of Chalmers’ response to related challenge posed by Keith Frankish

“In my view a (non-Russellian) dualist should probably endorse primitive subjects, holding that fundamental phenomenal properties are instantiated by fundamental entities (a kind of entity dualism or substance dualism).” (Chalmers, 2020)

This response falls back on Chalmers’ Dualist assumptions, which most researchers would find highly unpalatable.

What is needed for the Realist is some explanation of introspection that does not use the word “I” and does not assume controversial views like Dualism. One option of this sort would appeal to a mental state with a special relation to consciousness. For example, philosophers often appeal to the idea of ‘phenomenal concepts‘, which are special concepts that are used during introspection to represent and think about consciousness and its phenomenal character. These concepts, the idea goes, have some special direct relation to the consciousness, but the way these concepts work can be explained in physical-functional terms. Phenomenal concepts are typically used to counter dualism by providing an explanation for how an explanatory gap could exist without there being an actual metaphysical gap between the physical-function brain and consciousness: phenomenal concepts represent consciousness in a distinct way from descriptive concepts that represent the physical-functional properties. This creates a psychological gap between two kinds of mental representations of consciousness that leads to the explanatory gap. Thus, there is a physicalist (non-dualist) explanation for how an explanatory gap exists.

In the present context, the proponents of the phenomenal concept strategy could use the idea of phenomenal concepts to say something like Mary lacks consciousness and phenomenal concepts. Phenomenal concepts are usually described as having some direct relation to consciousness, so there would likely be some story here about how this direct relation provides people with justification for believing Realism is more plausible than Illusionism, which Mary, not having phenomenal concepts, would lack.

There are several issues with this approach. First, a challenge for phenomenal concept-like strategies is that it is not enough to argue that it is possible for such phenomenal concepts (with special relations to consciousness that justify Realism) to exist. One would have to argue it is more probable than not that they do exist. Remember, we are asking why humans should assign more credence to Realism than Illusionism, rather than just assigning 50/50. To do this, it is not enough to say there is possibly some special phenomenal concepts that provide humans with justification for assigning more credence to Realism, since the mere possibility of such concepts is consistent with a 50/50 assignment of credences.

As far as I can tell, however, the best that proponents of the phenomenal concept strategy have done is show it is only possible phenomenal concepts exist. There isn’t exactly an empirical research program around these ideas that have provided empirical evidence for their existence along with their special epistemic relations to consciousness.

Second, a key component of the phenomenal concept strategy is that such concepts can be explained in completely physical-functional terms. However, if such concepts are fully understandable in physical-functional terms, then Mary will understand everything about them since she knows all the physical-functional facts about the brain (!), including how and in what way they provide humans with justification for believing Realism. But now there is a contradiction. Remember, we are considering how Realists could defend position 2 — the view the Mary should be pro-Illusionist, but humans should be pro-Realist. However, if Mary has knowledge of the same facts that justify Realism for humans, then she will have access to such justification too. Thus, this phenomenal concept approach does not seem compatible with option 2.

Nor does this strategy seem able to defend option 1, the view Mary should place more credence on Realism. Let’s say Mary learns of the special epistemic properties phenomenal concepts provide humans for believing in Realism. What are these? It is just hard to imagine what this special epistemic properties could be, even if phenomenal concepts exist. Maybe something like phenomenal concepts exists that explains why people tend to have dualist intuitions and intuitions there is an explanatory gap. But, this is distinct from the claim these concepts also provide some special knowledge of phenomenal character. What is needed is reason to believe these concepts have something more that involves special epistemic justification for Realism. But, why think these concepts have some special properties that would justify believing in the hard problem and mysterious things like phenomenal character? It is not obvious. The only way I could see a Realist defending this view would be to beg the question, by assuming the existence of phenomenal character, then proceeding to explain some epistemic relation it has to phenomenal concepts.

Let’s consider one final possible response from Realists. Some Realists might argue it is simply obviously true that human’s have knowledge of phenomenal character and it is so obvious stipulation is sufficient to justify this position. The burden is instead on Illusionists to explain why it is insufficient, just as one might be required to explain why something we take to be basic data or a widely held axiom should not, in fact, be considered so.

But, the Mary scenario does seem to reverse this burden. Remember, option 2 for Realists argues Mary should conclude Illusionism is at least as plausible as Realism, but humans should conclude Realism is more plausible. Does this position not cry out for an explanation? What knowledge/justification do humans have to believe in phenomenal character that Mary lacks and how do humans get it? How can it be that Mary knows so much (she knows all the physical-functional facts about the brain, remember) and reasons in a valid manner, yet she is somehow incorrect in her conclusions, while humans are correct? This requires a coherent explanation from Realists.

Conclusions

In summary, this thought experiment presents a kind of dilemma for Realists. It seems Realists must choose between one of two challenging positions:

Position 1: Mary should favor Realism over Illusionism. The difficulty here is 1) any behavior data Mary can observe is equally consistent with Realism as it is with Illusionism, 2) any brain data Mary can observe provides her with no clear reason to believe phenomenal character exists, and 3) the fact Mary does not introspect phenomenal experience seems to, at best, complicate anti-Illusionist philosophical arguments and, at worst, remove most of their force.
Position 2: Mary is correct in concluding Illusionism is at least as plausible as Realism, but humans should favor Realism due to some special knowledge/justification they have that Mary lacks. The challenge here is in explaining how people acquire this special knowledge/justification that Mary lacks. The claim Mary can both be reasoning correctly yet be wrong begs for an explanation beyond just simple stipulation that people know something she doesn’t, but Realists have yet to develop any consensus around an argument as to why we should believe that humans have some special introspective knowledge/justification for believing in phenomenal character.

If Realists cannot meet these challenges, then it seems we must agree with Mary and accept Illusionism is at least as plausible as Realism. In other words, we must take Illusionism seriously.

If there is some counter-argument, criticism, or anything else you think I have missed, I would love to hear it! Please post in the comments.

Why are Consciousness Researchers So Resistant to Illusionism?

Introduction

Most consciousness researchers are “realists”. They believe consciousness has special “subjective character”, “what-it-is-likeness”, “phenomenal qualities”, etc. and explaining these qualities, i.e., why and how they arise from the neural processing, poses a very hard problem, maybe the hardest in all of science.

Illusionists, on the other hand, do not believe there exists any “subjective character”, “phenomenality”, etc., that needs to be explained, and, as a consequence, there is no hard problem of consciousness. Illusionism has received increased attention by philosophers and scientists over the last decade, but illusionists are still in the minority. Most consciousness researchers do not find illusionism plausible, and many even find it to be absurd.

Why aren’t more consciousness researchers sympathetic to illusionism? This is a question some illusionists are asking themselves. I ask myself the same question, since I, over the last few years, have become increasingly confident illusionists are right. Though I am not a consciousness researcher, I did closely study the philosophy and science of consciousness as an undergraduate and master’s student, and wrote a master’s thesis on the subject.

Those of us confident in the illusionist view must ask ourselves, is the majority opinion of consciousness experts a good truth-tracking statistic, in which case illusionists, like myself, are likely wrong? Or might there be some other reason(s) for the field’s resistance to illusionism, that is independent of illusionism’s plausibility?

Illusionists have argued previously that people naturally have anti-illusionist intuitions (e.g., see this from Francois Kammerer). It is very common for people to find illusionism to be, not only implausible, but absurd, suggesting there is a natural psychological anti-illusionist intuition. Philosophers like Keith Frankish have suggested this may be why illusionists are still a minority among consciousness researchers.

I believe this is at least part of the explanation. However, I think illusionists need more than this. One can still ask the question, even if people do have natural, anti-illusionist intuitions, why are consciousness researchers failing to override these intuitions with reason (i.e., with philosophical argumentation in support of illusionism)? Presumably scientists and philosophers are precisely the one’s who are best trained to follow reason (i.e., rational argument and the scientific method) wherever it goes, even if it leads to unintuitive or surprising conclusions. So why should we really think scientists and philosophers are so influenced by such naive intuitions?

I want to suggest the following hypothesis: if people have anti-illusionist intuitions, then these intuitions are likely to be unusually strong among consciousness researchers relative to other researchers. This may help form an explanation for why it is consciousness researchers are so influenced by their pre-philosophical intuitions. It also motivates more empirical analysis of our natural intuitions among researchers who do not specialize in consciousness research.

The Meta-Problem of Consciousness

Before explaining this view, we need to discuss some terms. The meta-problem is the problem of providing cognitive-neural explanations of why people tend to think there is a hard problem. More specifically, it is the problem of explaining problem intuitions. Problem intuitions are people’s tendencies to judge consciousness has certain mysterious/problematic properties. For example, explanatory intuitions are tendencies to judge there exists an explanatory gap between consciousness and physical-functional descriptions of the brain. Metaphysical intuitions are tendencies to judge consciousness has non-physical properties. Knowledge intuitions are tendencies to judge we have some special first-person knowledge of our own experiences and their subjective character. And so on.

Anti-Illusionist Intuitions: A Psychological Explanation

Several Illusionists (e.g., here) have previously argued that a problem intuition that needs explaining is the common intuition that illusionism is false. It is quite natural for most studying the philosophy and science of consciousness to find illusionism unpalatable, at best, and outright absurd at worst. And this intuition is present prior to hearing any of the philosophical arguments for or against illusionism, i.e., it is a naive, pre-philosophical intuition present upon hearing a description of the illusionist view. This does not mean it is wrong, just that it is not a result of considering philosophical arguments against illusionism. People just naturally feel the view is implausible, even prior to philosophical analysis. Philosophers like Frankish have suggested this intuition may be the reason consciousness researchers are, like most people, so resistant to illusionism: consciousness researchers, like most, will have this intuition and this biases their views and research against illusionism.

The Sampling Bias Hypothesis

I find the idea that people have natural, anti-illusionist intuitions plausible.

However, I believe there is additional a kind of selection bias in the population of consciousness researchers, i.e., consciousness researchers tend to have unusually strong anti-illusionist intuitions.

Here’s the basic argument:

People naturally have anti-illusionist intuitions, which are independent of illusionism’s philosophical merits (i.e., they are pre-philosophical, naive intuitions).
How much these anti-illusionist intuitions actually bias a researcher’s beliefs depends on the strength of the intuition: stronger the intuition the more probable and significant its effects.
Consciousness researchers have unusually strong anti-illusionist intuitions relative to the general population of researchers.
Consciousness researchers have an unusually strong bias against illusionism and this bias is independent of illusionism’s philosophical merit.

Proposition 4 follows from premises 1-3. I think premises 1-3 are quite plausible. Let’s consider each in turn.

Premise 1: People naturally have anti-illusionist intuitions, which are independent of illusionism’s philosophical merits (i.e., they are pre-philosophical, naive intuitions). This should not be controversial. First off, by ‘pre-philosophical’ anti-illusionist intuitions I just mean intuitions that exist prior to hearing the arguments against illusionism. I think it is fairly uncontroversial such intuitions exist given that is quite common for scientists and philosophers to immediately find illusionism absurd. Common arguments against illusionism often just begin with its general description and conclude it is just obvious such a view cannot be right, often on the basis of the common epistemic belief that “if we know anything it is that we are conscious”.

Premise 2: How much these anti-illusionist intuitions actually bias a researcher’s beliefs depends on the strength of the intuition: stronger the intuition the more probable and significant its effects. This premise is essentially true by definition. If we have a tendency to believe idea X is false, then by definition there is significant probability we will form the belief that X is false. A strong intuition that X is false essentially just means a strong probability one forms the belief X is false.

Premise 3: Consciousness researchers have unusually strong anti-illusionist intuitions relative to the general population of researchers. This premise is less obvious and more complex. Why should we believe consciousness researchers have unusually strong anti-illusionist intuitions relative to the general population of researchers?

This is an empirical claim and my evidence is admittedly anecdotal, but I think many others in the field will have had a similar experience. As a student, I seriously considered pursuing a career as a consciousness researcher. I quickly found there are not many jobs for consciousness researchers, to say the least, in both philosophy (whose job market is already abysmal) and science. Further, there is still some stigma (though not a strong as it once was) around researching consciousness, especially in the sciences, which could limit one’s career prospects even if one is lucky enough to find a job where they can investigate consciousness.

Given this situation, why would anyone try to become a consciousness researcher? When it comes to practical concerns, there are basically no reasons to pursue a career as a consciousness researcher and many reasons not to. Thus, there must be some other factor(s) motivating such people to do so.

As a student, I studied in multiple philosophy departments with other students and philosophers working on consciousness, and in UC Irvine’s cognitive science department, which is known to have an unusually large community of consciousness researchers. My experience talking to such researchers strongly suggests to me that these researchers are motivated by an unusual fascination with consciousness, so significant that their fascination outweighs the practical concerns that come with pursuing such a career. This makes sense. If one was not totally taken and fascinated with consciousness there would be little reason to pursue a career as a consciousness researcher.

Where does this unusually strong fascination originate? Why is consciousness so interesting to these people? Consciousness is interesting for multiple reasons. It, for example, is closely tied to moral theory, i.e., an agent’s ability to experience conscious states like pain are important for judging their moral status. Consciousness is also tied to ideas related to meaning: what, after all, is the point of life without first-person experience?

However, what makes consciousness unique relative to every other natural phenomena is its difficulty to explain: the hard problem of consciousness is often said to be the hardest problem in all of science. This sense of mystery is what got me so obsessed with consciousness, and my sense talking to other consciousness researchers was that it too was what made them obsessed. It is the deep mystery around consciousness that makes consciousness unique. It is what fills people like myself with a sense of wonder when thinking about consciousness. It is the reason people like myself get hooked on the subject and make risky career decisions to study it.

Notice, there is another way to describe this natural fascination with the deep mystery of consciousness: having a strong intuition/feeling that explaining consciousness is unusually difficult, and this is equivalent to having strong problem intuitions. Problems intuitions are those tendencies related to judging there is a hard problem of consciousness (see Chalmers original paper). Thus, having strong problem intuitions, put simply, just means having a strong sense there is a hard problem of consciousness. And thus, another way to say what I have just argued is that having strong problem intuitions is what drove many consciousness researchers to be fascinated with consciousness and to decide to go into consciousness research.

Now, if one has strong problem intuitions, this would also entail one has strong anti-illusionist intuitions. For example, having strong knowledge intuitions means have a strong sense that one has special knowledge of their own conscious experience, including its subjective character, etc. This entails premise 3: typically, one does not become a consciousness researcher unless one has unusually strong problem intuitions in the first place. Having strong problem intuitions, like knowledge intuitions, also means having strong anti-illusionist intuitions. Thus, consciousness researchers should be expected to have unusually strong anti-illusionist intuitions relative to the general population of researchers.

The result is that consciousness researchers will be much more influenced by their intuitions than the rest of the population of researchers, and they will be influenced in the direction of believing conscious is deeply mysterious and that views that contradict this, like illusionism, are false.

Now this argument does not necessarily mean realists are wrong, but it does raise the question of whether the popularity of realism is actually based on its philosophical plausibility rather than some naive and unusual intuitions held among consciousness researchers.

Conclusion

Much of this argument for proposition 3 is based on anecdotal data, i.e., my experience talking to graduate students, philosophers, and scientists working on consciousness. I think this anecdotal data is significant enough to justify proposing the hypothesis, but, of course, more empirical testing , possibly through surveys, will of course need to be done to determine how plausible it really is. I would love to see such testing.

An interesting implication of my argument, is that researchers who focus their research on topics other than consciousness, should naturally have less strong anti-illusionist intuitions than consciousness researchers. In my experience, there is plausibility to this implication as well. I find that neuroscientists and AI researchers, that do not work on consciousness, in particular, are much more likely to view the mind through an objective, mechanistic lens than a subjective, experience based one. The objective, mechanistic lens is much more conducive to the illusionist view: according to the illusionists, once we have a nice mechanistic explanation of why we think there is a hard problem we are done. No hard problem exists, so we only need to explain why we think one exists. One key example of an illusionist sympathizer in this community is Turing award winner and Nobel Laureate Geoffrey Hinton, who has explicitly stated his sympathies with illusionist thinking.

Whatever the case, I believe the arguments presented here and those previously by illusionists suggest that consciousness researchers should do a bit of honest self-study. Why do they find illusionism so unpalatable? Is it really due to good philosophical argument against the illusionist position? Or is it due largely naive, pre-philosophical, anti-illusionist intuitions that are unusually strong among consciousness researchers?

The Meta-Problem Test for AI Consciousness

by Nick Alonso

Artificial intelligence (AI) is rapidly improving and its progress shows no signs of slowing. Our understanding of consciousness, on the other hand, is limited and is progressing at a snails pace. This situation raises an obvious question: how should we judge whether advanced AI are conscious, given our understanding of consciousness is, and will likely continue to be, so limited?

Recent work has proposed two ways to approach this question: 1) use our best scientific theories of consciousness as a basis to make such judgments, or 2) devise and use a behavioral test to make such judgments. Both approaches, as I note below, face challenges.

In this post, I develop the beginnings of an alternative test for AI consciousness based on the ‘Meta-Problem’ of consciousness that does not fit cleanly in either of these categories. The meta-problem is the problem of explaining why people think they are conscious. For reasons I outline below, I believe this novel approach has interesting advantages over the other main approaches. I sketch the foundational ideas here in the hopes it could serve as a basis for further development.

Preliminaries

Before diving in, I need to define terms. The word ‘consciousness’ is ambiguous in the sense that people use it to refer to several different mental phenomena. ‘Self-consciousness’ refers, roughly, to the ability to mentally represent one’s own body and internal workings and to distinguish one’s self from the environment. A mental state or information in the brain is ‘access conscious’ if it is made widely available to a variety of cognitive systems. These two common definitions of consciousness are not what I will be discussing here. These are not especially mysterious or deeply difficult to identify in AI.

The sort of consciousness I will be discussing is what philosophers call ‘phenomenal consciousness’ or ‘subjective experience’. Examples of subjective experiences include first person experiences of color, pain/pleasure, sounds, tastes, smells, and emotions. For reasons I will not be getting into here, this is the mysterious sort of consciousness that has and continues to puzzle philosophers and scientists. The question of whether some AI can be conscious under this definition can be framed as, does the AI have first person experiences of the world? Does it have an inner mental life? Or is it all ‘dark inside’ for the AI, devoid of inner experience?

Most scientists and philosophers who study the subject will agree we are far from an agreed upon theory of the nature of subjective experience and its relation to the brain which creates an obvious challenge when trying to identify consciousness in AI.

This challenge is concerning from a moral point of view since many moral philosophers agree an agent’s moral status (i.e., what moral rights it does or does not have) depends in important ways on what conscious states it is capable of having, especially on its ability to have experiences with a pain/pleasure component. For a good discussion of this concern, I recommend the writings of philosopher Eric Schwitzgebel (e.g., here).

Background

I find it useful to split the problem of identifying consciousness in AI into two problems:

1) Identifying whether AI can be conscious. Following philosopher Susan Schneider, this is the problem of determining whether silicon (or otherwise non-carbon based) AI can support conscious experience, in principle. Some theories of consciousness entail artificial, non-carbon based systems can be conscious. Other theories disagree.

2) Identifying which AI systems are conscious. Even if we assume/discover non-carbon based artificial systems could support consciousness, in principle, there still remains the question of which subset of artificial systems are conscious and to what degree. This problem is analogous to the problem of identifying which subset of animals are conscious and to what degree, given we know biological-carbon based brains can support consciousness.

Philosophers and scientists who study consciousness commonly believe silicon can support consciousness, though agreement certainly is not universal. I suspect support for this belief will only grow in the coming years, and I make this assumption in what follows. Under this assumption, problem 2, the problem of which AI are conscious, becomes the focus.

How might we approach identifying which AI are conscious? Possible approaches are typically categorized into two types.

The theory-driven approach. This approach aims to use our best scientific theories of consciousness as a basis for making judgments about AI consciousness. For example, Butlin, Long, et al. recently showed that a handful of the leading theories of consciousness all seem to agree that certain computational properties are important for consciousness. They argue that these commonalities can be treated as ‘indicators’ of consciousness and used to make judgments about which AI are and are not conscious.

Challenge: The main challenge for theory-driven approaches is a deep lack of a consensus around the scientific methods for studying consciousness, around the requirements for a proper theory of consciousness, and around a theory of consciousness itself. This lack of consensus and shaky foundations suggest we should have limited confidence in, even our leading, theories of consciousness. For example, although Butlin, Long et al. provide a well developed theory-driven test for AI consciousness based on several popular theories, it is unclear how much trust we should put in the indicator properties pulled from these theories.

The theory-neutral approach. Theory-neutral approaches avoid the difficulties of the theory-driven approach by staying largely neutral with respect to scientific and philosophical theories of consciousness. Instead, consciousness-neutral approaches typically devise some sort of behavioral test that could help us determine whether some AI is conscious. One example, proposed by Susan Schneider and Edwin Turner, argues that if we train an AI model such that it is never taught anything about consciousness, yet it still ends up pondering the nature of consciousness, there is sufficient reason to believe it is conscious. Schneider and Turner imagine running this test on something like an advanced chatbot by asking it questions that avoid using the word ‘consciousness’, such as ‘would you survive the deletion of your program?’ The idea is that in order to provide a reasonable response, the AI would require a concept of something like consciousness, and the concept would have to originate from the AI’s inner conscious mental life, since the AI was not explicitly taught the concept during training.

Challenge: Philosophers have challenged theory-neutral approaches like this on the grounds that it seems possible, under a significant variety of views about consciousness, for a non-conscious AI to learn to act as if it is conscious, even when the AI is not explicitly taught to do so. Behavioral tests like those mentioned above would be unable to distinguish between non-conscious AI that learn to talk as if they are conscious from truly conscious AI. The reason theory-neutral approaches have this difficulty seems to be that they are too insensitive to the computational mechanisms causing the verbal reports, leaving open the possibility for non-conscious systems/cognitive mechanisms to generate behaviors that mimic those of conscious systems. To add to this problem, most of these tests rely on verbal reports and thus only apply to AI that can respond verbally.

The Meta-Problem of Consciousness

Below I present an alternative test for AI consciousness which can be interpreted as a middle point between theory-neutral and theory-driven approaches. The rough, first approximation of the test can be summarized as follows: if an AI says it is conscious for the same cognitive-computational reason that humans do, there is sufficient reason to believe the AI is conscious.

In order to develop this initial idea into a more rigorous and philosophically grounded test, we need to unpack a bit more what this statement means. First, what do I mean by “an AI says it is conscious for the same cognitive-computational reason that humans do“?

Humans who reflect on their own minds, tend to conclude they are conscious. We conclude we have a stream of first-person experiences, an inner mental life. We often conclude this stream of first person experience seems distinct from the neural mechanisms that underlie it, and make other related conclusions.

Now, why do people, who reflect on their own minds, tend to think these things? The standard line of thinking goes something like this: we think such things, of course, because we are conscious! We have conscious experiences, and these conscious experiences cause us to think we have conscious experiences.

This is the intuitive explanation, but it is not the only one. Philosophers and cognitive scientists have, in particular, shown that there exist consciousness-neutral explanations of the same behavior. That is, there exist explanations of why we think we are conscious that do not involve the term or concept of phenomenal consciousness.

Here is the basic idea: every behavior, including the behavior of saying you are conscious, is caused by some internal neural process, which implements some more abstract, cognitive-level computations. A description of a behavior’s neural and cognitive causes is what cognitive scientists and neuroscientists count as an explanation of the behavior: if we fully describe the neural and cognitive-computational processes that generate some common behavior X, then we have a (causal/mechanistic) explanation of why we observe X.

This line of thinking applies to any behavior, including common human behaviors associated with consciousness, such as our tendency to say we have a stream of first-person experiences. Put simply, there is some neural process, which implements more abstract cognitive level computations, that causes behaviors associated with consciousness. Thus, we can explain these behaviors in a consciousness-neutral way, in terms of these neural and cognitive mechanisms.

The problem of explaining why we think we have mysterious conscious states, has been given a name and developed into a research program by philosopher David Chalmers, who calls it the meta-problem of consciousness. The meta-problem gets its name from the fact that it is a problem about a problem: it is the problem of explaining why we think we have consciousness states that are problematic to explain.

What is nice about these recent developments on the meta-problem by Chalmers and others, is that they provide ideas which, as I will explain, are useful for setting the foundation for a test for AI consciousness based on our preliminary idea above (i.e., the idea that if an AI claims it is conscious for the same cognitive reason people do, it should be identified as conscious). In particular, I focus on three ideas developed around the meta-problem and use them to develop a test for AI consciousness.

First, is the idea that our tendency to say or judge we have consciousness involves two parts: a lower order mental model, usually some sort of perceptual-like model and a higher-order model, which represents the lower order model (see Chalmers, 2019, pp. 40-45). The higher-order model can be described as the high-level ‘thought’ about the lower order model, and the lower order model can, in this way, be thought of as the mechanistic source of our thoughts about consciousness. To simplify terminology, I will just call this mechanistic source of our judgments about consciousness the c-source.

To make this more concrete, consider an example of a c-source which comes from attention schema theory (AST). AST is one of the most well-developed approaches to the meta-problem. AST claims the brain has a simplified model of attention, an attention schema, which it uses to control attention. This simplified model represents attention as a simple mental relation. So, when our cognition reads out the content from this model, it concludes we have some simple, primitive mental relations between ourselves and features of the world. We call these simple, mental relations ‘awareness’ or ‘experience’ or ‘consciousness’, and conclude they seem different, and non-reducible to the physical stuff in our brain. Now, AST may be incorrect, but it provides a clear illustration of what a c-source could be, i.e., a simplified mental model of attention.

The second idea is the hypothesis our c-source must be very closely related to consciousness. Now this point is not essential to the meta-problem. However, Chalmers argues for this point (see 2019, pp. 49-56), and it makes some sense. Most people assume conscious experience is itself the source of our claims we are conscious. As such, it would be highly surprising if the c-source, which play roughly the same causal role in cognition as consciousness, has no essential relation consciousness. For example, if AST is true, it would be very surprising if we concluded attention schemas had nothing to do with consciousness, since AST seems to entail that a thought like ‘I am have conscious experience X’ is actually referring to an attention schema (and/or their contents)! The c-source is in some sense what we are thinking about what we think about consciousness, and it thus seems that in order to avoid certain philosophical problems (explained in the meta-problem paper but not here), a theory of consciousness must assume there is some essential relation between consciousness and the c-source.

The third idea is a general/high-level description of what the c-source likely is. Now there is no consensus around a solution to the meta-problem. However, dozens of ideas have been developed, in addition to AST, which can be used as a starting point. Similar to the theory-driven approach of Butlin, Long, et al., we can look at promising approaches to the meta-problem and ask whether there are any commonalities between them that can be used as a basis for an AI consciousness test. Fortunately, Chalmers provides an extensive review of proposed solutions to the meta-problem, summarizes some common threads between them, and synthesizes ideas he found promising, which I find promising as well. Here is his summary

We have introspective models deploying introspective concepts of our internal states that are largely independent of our physical concepts. These concepts are introspectively opaque, not revealing any of the underlying physical or computational mechanisms. Our perceptual models perceptually attribute primitive perceptual qualities to the world, and our introspective models attribute primitive mental relations to those qualities. We seem to have immediate knowledge that we stand in these primitive mental relations to primitive qualities, and we have the sense of being acquainted with them .
Chalmers, The Meta-Problem of Consciousness (2018, p.34).

There is a lot to unpack in this passage. Most of it is out of the scope of this post. The part important for understand the c-source, Chalmers suggests, likely involves simplified mental models of features/qualities in the world and simplified models of mental relations. The idea is our brain models certain features in the world (e.g., color) as primitive (irreducible) qualities, and our brain models certain mental relations as primitive (irreducible) relations between us and these qualities. This gives us the sense we have direct first person experiences of qualities like, e.g., color, sound, and tactile sensations. These simplified models are thus our c-sources. This idea may not be completely right, but it is a nice starting point that encompasses the claims of a range of proposed solutions to the meta-problem, including prominent ones like AST.

Summary of the foundational ideas for the MPT:

There is a cognitive source of our tendency to judge we are conscious (what I call the c-source), which can be described in consciousness-neutral terms.
There are a priori (philosophical) reasons to believe the c-source has an essential link to consciousness.
An initial theory that encompasses ideas from a range of hypotheses of the c-source says the c-source is a set of simplified/compressed mental representations of features in the world and our mental relations to the features.

The Meta-Problem Test for AI Consciousness

I will now use these ideas to construct what I will call the meta-problem test (MPT) for AI consciousness. After presenting the MPT here, I discuss its advantages over the other approaches. My proposal for the MPT rests on the following assumption

The Foundational Assumption for the MPT: the presence of the c-source in an AI provides sufficient reason to believe the AI is conscious (under the assumption silicon-based systems can be conscious, in principle). The absence of the c-source is sufficient reason to believe an AI is not conscious.

This assumption does not claim the presence of a c-source is sufficient for consciousness, just sufficient for us to believe consciousness is present. Thus, the claim it is making about consciousness is relatively weak, as it makes no specific claims about the necessary and sufficient conditions for consciousness, what consciousness is, or its metaphysical relation to the brain. It just says the presence of the c-source is evidence enough for consciousness, and its absence is evidence enough for consciousness’ absence.

This assumption is supported by the second idea discussed above, which is that the c-source likely has some essential relation to consciousness. Further philosophical work is needed to determine the plausibility of this point. As noted above, Chalmers provides some arguments as to why we should think there is some direct, essential relation between consciousness and, what I am calling, the c-source, (see pp. 40-45). I will not got into the details of these arguments here but will try to in future posts. For now, I only note that this foundational assumption has prima facie plausibility.

Under this assumption we can lay out the basic steps for implementing the (MPT):

Put cognitive scientists to work on the meta-problem until the field converges to an explanation of what the c-source is in people, using Chalmers’ suggestion, and related theories, as a starting point.
Develop systematic methods for identifying the c-source in AI.
Judge those AI with the c-source to be conscious. Judge those AI without the c-source to be unconscious.

The Advantages of the MPT

How does the MPT compare to more standard theory-driven and theory-neutral approaches? Interestingly, the MPT does not cleanly fit into either category.

Like the theory-driven approach the MPT proposes using a scientific theory of a mental process as a basis for making judgments about AI consciousness. However, unlike the theory-driven approach, the mental process this theory is about is not consciousness itself, but instead a cognitive process that is very closely related to consciousness, the c-source.

Like theory-neutral approaches the MPT remains relatively neutral w.r.t. scientific and philosophical theories of consciousness, with the exception of its foundational assumption. However, unlike typical theory-neutral approaches, the MPT still relies on test for a certain mental process (the c-source) based on scientific theories of what that mental process is. Also, the MPT is a cognitive-based test: it tests whether a certain cognitive process/representation is present and if it is we judge consciousness is present too, whereas theory-neutral approaches tend to be more behavior focused and less sensitive to the cognitive mechanisms generating the behavior in question.

The MPT thus does not fit neatly into either category, yet it shares some properties with both approaches. Interestingly, this middle ground may allow the MPT to avoid the main problems associated with theory-neutral and theory-driven approaches, while keeping some of their advantages.

More specifically, the advantages of the MPA over theory-driven approaches are

The MPT does not rely on any scientific theories of consciousness, and therefore avoids the uncertainty that necessarily comes with these theories and their assumptions. Although the MPT does rely on the assumption that the presence of the c-source is sufficient reason to believe consciousness is present, this assumption is much weaker, and therefore should be more easily defended, than the stronger more specific claims of scientific theories of consciousness.
The theories the MPT does rely on attempt to explain a cognitive process, the c-source, which is not philosophically problematic like consciousness. As such it is much more likely we can make progress on finding widely accepted theories of the c-source in the short-term than we can with theories of consciousness.

The advantages of the MPT over theory-neutral approaches are as follows:

Arguably, the central issue for behavioral-based, theory-neutral tests is that such tests cannot distinguish reliably enough between non-conscious AI that behave as if they are conscious, from genuine conscious AI. This issue is largely a result of the fact these tests are too insensitive to the cognitive processes generating the relevant behaviors. The MPT, alternatively, is a cognitive-based test that only identifies those AI with a certain kind of cognitive process to be conscious. If the foundational assumption of the MPT is correct, the MPT avoid the central issue facing behavioral-based tests, as it will be able to reliably distinguish between non-conscious AI that merely behave as if they are conscious (which are those that behave conscious-like but through a process unrelated to the c-source) from those that actually are conscious (which will be those that behave conscious-like through a process that is rooted in the c-source).
The MPT, unlike many proposed theory-neutral approaches, does not rely solely on language generation. The MPT can also use non-language based tests. For example, if AST turns out to be true, we could test for the presence of attention schemas in an AI by having it perform tasks that require a certain kind of control over its attention, which only an attention schema can provide. Further, we can also perform the MPT using non-behavioral tests which directly probe the AI’s computational mechanisms for the c-source, e.g., directly study an AI’s artificial neural network for the presence of self-representations of attention. This allows us to test for consciousness in a wider variety of AI than linguistic tests allow for and it allows us to evidence our judgments about AI consciousness in a wider variety of ways than linguistic and behavioral tests can alone.

Current Limitations of the MPT

The MPT is not without limitations:

The MPT approach is based on the assumption that the c-source is a very reliable indicator of consciousness. Although there is, in my opinion, good philosophical arguments for this assumption, more discussion is needed to determine whether it can be justified sufficiently to justify the use of the MPT.
The MPT approach requires that cognitive scientists actually make progress on the meta-problem. Very few cognitive scientists and consciousness researchers are currently working on the meta-problem directly. It remains to be seen if consciousness scientists will shift focus in the near-term.

Conclusions

The MPT offers a kind of middle point between typical theory-driven and theory-neutral approaches for AI consciousness tests.
As such, the MPT seems to retain the best aspects of both, while avoiding the problems associated with each. This suggests the MPT is a promising avenue for further development.
The success of the MPT depends heavily on the foundational assumption, that the c-source has some essential tie to consciousness. This assumption has prima facie plausibility but further analysis of it is needed.
The success of the MPT also depends on cognitive scientists converging toward a consensus on the c-source. This will only happen if significantly more scientists work directly on the meta-problem than there currently are.