Are Weird Aliens Conscious? Three Arguments (Two of Which Fail)

Most scientists and philosophers of mind accept some version of what I'll call "substrate flexibility" (alternatively "substrate independence" or "multiple realizability") about mental states, including consciousness. Consciousness is substrate flexible if it can be instantiated in different types of physical system -- for example in a squishy neurons like ours, in the silicon chips of a futuristic robot, or in some weird alien architecture, carbon based or not.

Imagine we encounter a radically different alien species -- one with a silicon-based biology, perhaps. From the outside, they seem as behaviorally sophisticated as we are. They build cities, fly spaceships, congregate for performances, send messages to us in English. Intuitively, most of us would be inclined to say that yes, such aliens are conscious. They have experiences. There is "something it's like" to be them.

But can we argue for this intuition? What if carbon is special? What if silicon just doesn't have the je ne sais quoi for consciousness?

This kind of doubt isn't far fetched. Some people are skeptical of the possibility of robot consciousness on roughly these grounds, and some responses to the classic "problem of other minds" rely on our biological as well as behavioral similarity to other humans.

If we had a well-justified universal theory of consciousness -- one that applies equally to aliens and humans -- we could simply apply it. But as I've argued elsewhere, we don't have such a theory and we likely won't anytime soon.

Toward the conclusion that behaviorally sophisticated aliens would be conscious regardless of substrate, I see three main arguments, two of which fail.

Argument 1: Behavioral Sophistication Is Best Explained by Consciousness

The thought is simple. These aliens are, by hypothesis, behaviorally sophisticated. And the best explanation for sophisticated behavior is that they have inner conscious lives.

There are two main problems with this argument.

First, unconscious sophistication. In humans, unconscious behavior often displays complexity without consciousness. Bipedal walking requires delicate, continuous balancing, quickly coordinating a variety of inputs, movements, risks, and aims -- mostly nonconscious. Expert chess players make rapid judgments they can't articulate, and computers beat those same experts without any consciousness at all.

Second, question-begging. This argument simply assumes what the skeptic denies: that the best explanation for alien behavior is consciousness. But unless we have a well justified, universally applicable account of the difference between conscious and unconscious processing -- which we don't -- the skeptic should remain unmoved.

Argument 2: The Functional Equivalent of a Human Could Be Made from a Different Substrate

This argument has two steps:

(1.) A functional equivalent of you could be made from a different substrate.

(2.) Such a functional equivalent would be conscious.

One version is David Chalmers' gradual replacement or "fading qualia" argument. Imagine swapping your neurons, one by one, with silicon chips that are perfect functional equivalents. If this process is possible, Premise 1 is true.

In defense of Premise 2, Chalmers appeals to introspection: During the replacement, you would notice no change. After all, if you did notice a change, that would presumably have downstream effects on your psychology and/or behavior, so functional equivalence would be lost. But if consciousness were fading away, you should notice it. Since you wouldn't, the silicon duplicate must be conscious.

Both premises face trouble.

Contra Premise 1, as Rosa Cao, Ned Block, Peter Godfrey-Smith and others have argued, it is probably not possible to make a strict functional duplicate out of silicon. Neural processing is subserved by a wide variety of low level mechanisms -- for example nitric oxide diffusion -- that probably can't be replicated without replicating the low-level chemistry itself.

Contra Premise 1, as Ned Block and I have argued, there's little reason to trust introspection in this scenario. If consciousness did fade during the swap, whatever inputs our introspective processes normally rely on will be perfectly mimicked by the silicon replacements, leaving you none the wiser. This is exactly the sort of case where introspection should fail.

[DON'T PANIC! It's just a weird alien (image source)]

Argument 3: The Copernican Argument for Alien Consciousness

This is the argument I favor, developed in a series of blog posts and a paper with Jeremy Pober. According to what Jeremy and I call The Copernican Principle of Consciousness, among behaviorally sophisticated entities, we are not specially privileged with respect to consciousness.

This basic thought is, we hope, plausible on its face. Imagine a universe with at least a thousand different behaviorally sophisticated species, widely distributed in time and space. Like us, they engage in complex, nested, long-term planning. Like us, they communicate using sophisticated grammatical language with massive expressive power. Like us, they cooperate in complex, multi-year social projects, requiring the intricate coordination of many individuals. While in principle it's conceivable that only we are conscious and all these other species are merely nonconscious zombies, that would make us suspiciously special, in much the same way it would be suspiciously special if we happened to occupy the exact center of the universe.

Copernican arguments rely on a principle of mediocrity. Absent evidence to the contrary, we should assume we don't occupy a special position. If we alone were conscious, or nearly alone, we would occupy a special position. We'd be at the center of the consciousness-is-here map, so to speak. But there's no reason to think we are lucky in that way.

Imagine a third-party species with a consciousness detector, sampling behaviorally sophisticated species. If they find that most or all such species are conscious, they won't be surprised when they find that humans, too, are conscious. But if species after species failed, and then suddenly humans passed, they would have to say, "Whoa, something extraordinary is going on with these humans!" It's that kind of extraordinariness that Copernican mediocrity tells us not to expect.

Why do we generally think that behaviorally sophisticated weird aliens would be conscious? I don't think the core intuition is that you need consciousness to explain sophistication or that the aliens could be functionally exactly like us. Rather, the core intuition is that there's no reason to think neurons are special compared to any other substrate that can support sophisticated patterns of behavior.

Three Epistemic Problems for Any Universal Theory of Consciousness

By a universal theory of consciousness, I mean a theory that would apply not just to humans but to all non-human animals, all possible AI systems, and all possible forms of alien life. It would be lovely to have such a theory! But we're not at all close.

This is true sociologically: In a recent review article, Anil Seth and Tim Bayne list 22 major contenders for theories of consciousness.

It is also true epistemically. Three broad epistemic problems ensure that a wide range of alternatives will remain live for the foreseeable future.

First problem: Reliance on Introspection

We know that we are conscious through, presumably, some introspective process -- through turning our attention inward, so to speak, and noticing our experiences of pain, emotion, inner speech, visual imagery, auditory sensation, and so on. (What is introspection? See my SEP encyclopedia entry Introspection and my own pluralist account.)

Our reliance on introspection presents three methodological challenges for grounding a universal theory of consciousness:

(A.) Although introspection can reliably reveal whether we are currently experiencing an intense headache or a bright red shape near the center of our visual field, it's much less reliable about whether there's a constant welter of unattended experience or whether every experience comes with a subtle sense of oneself as an experiencing subject. The correct theory of consciousness depends in part on the answer to such introspectively tricky questions. Arguably, these questions need to be settled introspectively first, then a theory of consciousness constructed accordingly.

(B.) To the extent we do rely on introspection to ground theories of consciousness, we risk illegitimately presupposing the falsity of theories that hold that some conscious experiences are not introspectable. Global Workspace and Higher-Order theories of consciousness tend to suggest that conscious experiences will normally be available for introspective reporting. But that's less clear on, for example, Local Recurrence theories, and Integrated Information Theory suggests that much experience arises from simple, non-introspectable, informational integration.

(C.) The population of introspectors might be much narrower than the population of entities who are conscious, and the first group might be unrepresentative of the latter. Suppose that ordinary adult human introspectors eventually achieve consensus about the features and elicitors of conscious in them. While indeed some theories could thereby be rejected for failing to account for ordinary human adult consciousness, we're not thereby justified in universalizing any surviving theory -- not at least without substantial further argument. That experience plays out a certain way for us doesn't imply that that it plays out similarly for all conscious entities.

Might one attempt a theory of consciousness not grounded in introspection? Well, one could pretend. But in practice, introspective judgments always guide our thinking. Otherwise, why not claim that we never have visual experiences or that we constantly experience our blood pressure? To paraphrase William James: In theorizing about human consciousness, we rely on introspection first, last, and always. This centers the typical adult human and renders our grounds dubious where introspection is dubious.

Second problem: Causal Confounds

We humans are built in a particular way. We can't dismantle ourselves and systematically tweak one variable at a time to see what causes what. Instead, related things tend to hang together. Consider Global Workspace and Higher Order theories again: Processes in the Global Workspace might almost always be targeted by higher order representations and vice versa. The theories might then be difficult to empirically distinguish, especially if each theory has the tools and flexibility to explain away putative counterexamples.

If consciousness arises at a specific stage of processing, it might be difficult to rigorously separate that particular stage from its immediate precursors and consequences. If it instead emerges from a confluence of processes smeared across the brain and body over time, then causally separating essential from incidental features becomes even more difficult.

Third problem: The Narrow Evidence Base

Suppose -- very optimistically! -- that we figure out the mechanisms of consciousness in humans. Extrapolating to non-human cases will still present an intimidating array of epistemic difficulties.

For example, suppose we learn that in us, consciousness occurs when representations are available in the Global Workspace, as subserved by such-and-such neural processes. That still leaves open how, or whether, this generalizes to non-human cases. Humans have workspaces of a certain size, with a certain functionality. Might that be essential? Or would literally any shared workspace suffice, including the most minimal shared workspace we can construct in an ordinary computer? Human workspaces are embodied in a living animal with a metabolism, animal drives, and an evolutionary history. If these features are necessary for consciousness, then conclusions about biological consciousness would not carry over to AI systems.

In general, if we discover that in humans Feature X is necessary and sufficient for consciousness, humans will also have Features A, B, C, and D and lack Features E, F, G, and H. Thus, what we will really have discovered is that in entities with A, B, C, and D and not E, F, G, or H, Feature X is necessary and sufficient for consciousness. But what about entities without Feature B? Or entities with Feature E? In them, might X alone be insufficient? Or might X-prime be necessary instead?

The obstacles are formidable. If they can be overcome, that will be a very long-term project. I predict that new theories of consciousness will be added faster than old theories can be rejected, and we will discover over time that we were even further away from resolving these questions in 2025 than we thought we were.

[a portion of a table listing theories of consciousness, from Seth and Bayne 2022]

Types and Degrees of Turing Indistinguishability; Thinking and Consciousness

Types and Degrees of Indistinguishability

The Turing test (introduced by Alan Turing in a 1950 article) treats linguistic indistinguishability from a human as sufficient grounds to attribute thought (alternatively, consciousness) to a machine. Indistinguishability, of course, comes in degrees.

In the original setup, a human and a machine, through text-only interface, each try to convince a human judge that they are human. The machine passes if the judge cannot tell which is which. More broadly, we might say that a machine "passes the Turing test" if its textual responses strike users as sufficiently humanlike to make the distinction difficult.

[Alan Turing in 1952; image source]

Turing tests can be set with a relatively low or high bar. Consider a low-bar test:

* The judges are ordinary users, with no special expertise.
* The interaction is relatively brief -- maybe five minutes.
* The standard of indistinguishability is relaxed -- maybe if 20% of users guess wrong, that suffices.

Contrast that with a high-bar test:

* The judges are experts in distinguishing humans from machines.
* The interaction is relatively long -- an hour or more.
* The standard of indistinguishability is stringent -- if even 55% of judges guess correctly, the machine fails.

The best current language models already pass a low-bar test. But it will be a long time before language models pass this high-bar test, if they ever do. So let's not talk about whether machines do or not pass "the" Turing test. There is no one Turing test.

The better question is: What type and degree of Turing-indistinguishability does a machine possess? Indistinguishability to experts or non-experts? Over five minutes or five hours? With what level of reliability?

We might also consider topic-based or tool-relative Turing indistinguishability. A machine might be Turing indistinguishable (to some judges, for some duration, to some standard) when discussing sports and fashion, but not when discussing consciousness, or vice versa. It might fool unaided judges but fail when judges employ AI detection tools.

Turing himself seems to have envisioned a relatively low bar:

I believe that in about fifty years' time it will be possible, to programme computers... to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning (Turing 1950, p. 442)

I've bolded Turing's implied standards of judge expertise, indistinguishability threshold, and duration.

What bar should we adopt? That depends on why we care about Turing indistinguishability. For a customer service bot, indistinguishability by ordinary people across a limited topic range for brief interaction might suffice. For an "AI girlfriend", hours of interaction might be expected, with occasional lapses tolerated or even welcomed.

Turing Tests for Real Thinking and Consciousness?

But maybe you're interested in the metaphysics, as I am. Does the machine really think? Is it really conscious? What kind and degree of Turing indistinguishability would establish that?

For thinking, I propose that when it becomes practically unavoidable to treat the machine as if it has a particular set of beliefs and desires that are stable over time, responsive to its environment, and idiosyncratic to its individual state, then we might as well say that it does have beliefs and desires, and that it thinks. (My own theory of belief requires consciousness for full and true belief, but in such a case I don't think it will be practical to insist on this.)

Current language models aren't quite there. Their attitudes lack sufficient stability and idiosyncrasy. But a language model integrated into a functional robot that tracks its environment and has specific goals would be a thinker in this sense. For example: Nursing Bot A thinks the pills are in Drawer 1, but Nursing Bot B, who saw them moved, knows that they're in Drawer 2. Nursing Bot A would rather take the long, safe route than the short, riskier route. We will want attribute sometimes true, sometimes false environment-tracking beliefs and different stable goal weightings. Belief, desire, and thought attribution will be too useful to avoid.

For consciousness, however, I think we should abandon a Turing test standard.

Note first that it's not realistic to expect any machine ever to pass the very highest bar Turing test. No machine will reliably fool experts who specialize in catching them out, armed with unlimited time and tools, needing to exceed 50% accuracy by only the slimmest margin. To insist on such a high standard is to guarantee that no machine could ever prove itself conscious, contrary to the original spirit of the Turing test.

On the other hand, given enough training and computational power, machines have proven to be amazing mimics of the superficial features of human textual outputs, even without the type of underlying architecture likely to support a meaningful degree of consciousness. So too low a bar is equally unhelpful.

Is there reason to think that we could choose just the right mid-level bar -- high enough to rule out superficial mimicry, low enough not to be a ridiculously unfair standard?

I see no reason to think there must be some "right" level of Turing indistinguishability that reliably tests for consciousness. The past five years of language-model achievements suggest that with clever engineering and ample computational power, superficial fakery might bring a nonconscious machine past any reasonable Turing-like standard.

Turing never suggested that his test was a test of consciousness. Nor should we. Turing indistinguishability has potential applications, as described above. But for assessing consciousness, we'll want to look beyond outward linguistic behavior -- for example, to interior architecture and design history.

Ten Purportedly Essential Features of Consciousness

The Features

Take a moment to introspect. Examine a few of your conscious experiences. What features do they share -- and might these features be common to all possible experiences? Let's call any such necessarily universal features essential.

Consider your visual experience of this text. Next, form an image of your house or apartment as viewed from the street. Think about what you'd do if asked to escort a crocodile across the country. Conjure some vivid annoyance at your second-least-favorite politician. Notice some other experiences as well -- a diverse array. Let's not risk too narrow a sample.

Of course, all of these examples share an important feature: You are introspecting them as they occur. So to do this exercise more properly, consider also some past experiences you weren’t introspecting at the time. Try recalling some emotions, thoughts, pains, hungers, imagery, sensations. If you feel unconfident -- good! You should be. You can re-evaluate later.

Each of the following features is sometimes described as universal to human experience.

1. Luminosity. Are all of your experiences inherently self-representational? Does the having of them entail, in some sense, being aware of having them? Does the very experiencing of them entail knowing them or at least being in a position to know them? Note: These are related, rather than equivalent, formulations of a luminosity principle.

[porch light; image source]

2. Subjectivity. Does having these experiences entail having a sense of oneself as a subject of experience? Does the experience have, so to speak, a "for-me"-ness? Do the experiences entail the perspective of an experiencer? Again, these are not equivalent formulations.

3. Unity. If, at any moment, there's more than one experience, or experience-part, or experience-aspect, are they all subsumed within some larger experience, or joined together in a single stream, so that you experience not just A and B and C separately but A-with-B-with-C?

4. Access. Are these experiences all available for a variety of "downstream" cognitive processes, like inference and planning, verbal report, and long-term memory? Presumably yes, since you're remembering and considering them now. (I'll discuss the methodological consequences of this below.)

5. Intentionality. Are all of your experiences "intentional" in the sense of being about or directed at something? Your image of your house concerns your house and not anyone else's, no matter how visually similar. Your thoughts about Awful Politician are about, specifically, Awful Politician. Your thoughts about squares are about squares. Are all of your experiences directed at something in this way? Or can you have, for example, a diffuse mood or euphoric orgasm that isn't really about anything?

6. Flexibility. Can these experiences, including any fleeting ones, all potentially interact flexibly with other thoughts, experiences, or aspects of your cognition -- as opposed to being merely, for example, parts of a simple reflex from stimulus to response?

7. Determinacy. Are all such experiences determinately conscious, rather than intermediately or kind-of or borderline conscious? Compare: There are borderline cases of being bald, or green, or an extravert. Some theorists hold that borderline experientiality is impossible. Either something is genuinely experienced, however dimly, or it is not experienced at all.

8. Wonderfulness. Are your experiences wonderful, mysterious, or meta-problematic – there is no standard term for this – in the following technical sense: Do they seem (perhaps erroneously) irreducible to anything physical or functional, conceivably existing in a ghost or without a body?

9. Specious present. Are all of your experiences felt as temporally extended, smeared out across a fraction of a second to a couple of seconds, rather than being strictly instantaneous?

10. Privacy. Are all of your experiences directly knowable only to you, through some privileged introspective process that others could never in principle share, regardless how telepathic or closely connected?

I've presented these possibly essential features of experience concisely and generally. For present purposes, an approximate understanding suffices.

I've bored/excited you [choose one] with this list for two reasons. First, if any of these features are genuinely essential for consciousness, that sets constraints on what animals or AI systems could be conscious. If luminosity is essential, no entity could be conscious without self-representation. If unity is essential, disunified entities are out. If access is essential, consciousness requires certain kinds of cognitive availability. And so on.

I'll save my second reason for the end of this post.

Introspection and Memory Can't Reveal What's Essential

Three huge problems ruin arguments for the essentiality of any of these features, if those arguments are based wholly on introspective and memorial reflection. The problems are: unreliability, selection bias, and the narrow evidence base.

Unreliability. Even experts disagree. Thoughtful researchers arrive at very different views. Given this, either our introspective processes are unreliable, or seemingly ordinary people differ wildly in the structure of their experience. I won't detail the gory history of introspective disagreement about the structure of conscious experience, but that was the topic of my 2011 book. Employing appropriate epistemic caution, doesn't it seem possible that you could be wrong about the universality, or not, of such features in your experience? The matter doesn't seem nearly as indubitable as that you are experiencing red, when you're looking directly at a nearby bright red object in good light, or that you're experiencing pain when you drop a barbell on your toe.

Selection bias. If any of your experiences are unknowable, you won't of course know about them. To infer luminosity from your knowledge of all the experiences you know about would be like inferring that everyone is a freemason from a sampling of regulars at the masonic lodge. Likewise, if any of your experiences fail to impact downstream cognition, you wouldn't reflect on or remember them. Methodological paradox doesn't infect the other features quite as inevitably, but selection bias remains a major risk. Maybe we have disunified experiences which elude our introspective focus and are quickly forgotten. Similarly, perhaps, for indeterminate or inflexible experiences, or atemporal experiences, or experiences unaccompanied by self-representation.

Narrow evidence base. The gravest problem lies in generalization beyond the human case. Waive worries about unreliability and selection bias. Assume that you have correctly discerned that, say, seven of the ten proposed features belong to all of your experiences. Go ahead and generalize to all ordinary adult humans. It still doesn't follow that these features are essential to all possible conscious experiences, had by any entity. Maybe lizards or garden snails lack luminosity, subjectivity, or unity. Since you can't crawl inside their heads, you can't know by introspection or experiential memory. (In saying this, am I assuming privacy? Yes, relative to you and lizards, but not as a universal principle.) Even if we could somehow establish universality among animals, it wouldn't follow that those same features are universal to AI cases. Maybe AI systems can be more disunified than any conscious animal. Maybe AI systems can be built to directly access each other's experiences in defiance of animal privacy. Maybe AI systems needn't have the impression of the wonderful irreducibility of consciousness. Maybe some of their conscious experiences could occur in inflexible reflex patterns.

Nor Will Armchair Conceptual Analysis Tell Us What's Essential

If you want to say that all conscious systems must have one or more of unity, flexibility, privacy, luminosity, subjectivity, etc., you'll need to justify this insistence with something sturdier than generalization from human cases. I see two candidate justifiers: the right theory of consciousness or the right concept of consciousness.

Concerning the concept of consciousness, I attest the following. None of these features are essential to my concept of consciousness. Nor, presumably, are those features essential to the concepts of anyone who denies their universal applicability. One or more of these features might be universally present in humans, or even in all animals and AI systems that could ever be bred or built; but if so, that's a fact about the world, not a fact that follows simply from our shared concept of consciousness.

In defining a concept, you get one property for free. Every other property must be logically proved or empirically discovered. I can define a rectangle via one (conjunctive) property: that of being a closed, right-angled, planar figure with four straight sides. From this, it logically follows that it must have four interior angles. I can define gold as whatever element or compound is common to certain shiny, yellowish samples, and then empirically discover that it is element 79.

Regarding consciousness, then: None of the ten purported essential properties logically follow from phenomenal consciousness as ordinarily defined and understood (generally by pointing to examples). None are quite the same as the target concept. You can choose to define "consciousness" differently, for example, via the conjunctive property of being both a conscious experience in the ordinary sense and one that is knowable by the subject as it occurs. Then of course luminosity follows. But you've changed the topic, winning by definitional theft what you couldn't earn by analytic hard work.

Could luminosity, subjectivity, unity, etc., covertly belong to the concept of consciousness, so that the right type of armchair (not empirical) reflection would reveal that all possible conscious experiences in every possible conscious entity must necessarily be luminous, subjective, or unified? Could subtle analytic hard work reveal something I'm missing? I can't prove otherwise. If you think so, I await your impressive argument. Even Kant held only that luminosity, subjectivity, and unity were necessary features of our experience, not of all possible experiences in all possible beings.

Set aside purely conceptual arguments, then. If we hope to defend the essentiality of any of these ten features, we'll need an empirically justified universal theory of consciousness.

That brings me to the second reason I've presented this feature list. I conjecture that universal theories of consciousness, intended to apply to all possible beings, instead of justifying the universality of (one or more of) these features circularly assume the universality of (one or more of) these features. Developing this conjecture will have to wait for another day.

A Dilemma for Nonlocal Theories of Consciousness

Call a theory of consciousness nonlocal if two entities that are molecule-for-molecule perfectly similar in their physical structure could nonetheless differ in their conscious experiences. My thought today is: Nonlocal theories of consciousness face an unattractive dilemma between (a.) allowing for physically implausible means of knowledge or (b.) allowing for the in-principle introspective inaccessibility of consciousness.

Clarifications:

Of course everyone agrees that entities with different causal histories and environments will tend to differ in their physical structure. Nonlocality requires the more unusual (and, to many, unintuitive) view that two entities could differ in their conscious experiences even if their local physical structure were somehow exactly the same.

I intend the "could" in "could nonetheless differ" to reflect natural or nomic possibility, that is, consistency with the laws of nature, rather than conceptual or metaphysical possibility. So a view, for example, that holds that consciousness-lacking "zombie" twins of us are metaphysically but not nomically possible still counts as a local theory if molecule-for-molecule locally identical twins would be nomically guaranteed to have the same conscious experiences.

"Local" needn't mean "in the brain". Theories on which conscious experience depends on states of the body or nearby environment still count as local in the intended sense. I won't try to draw a principled line between local and nonlocal, but nonlocal theories of the sort I have in mind make consciousness depend on events far away or deep in the past.

For sake of this argument, I'm assuming the falsity of certain types of dualist and non-naturalist views. If consciousness depends on an immaterial substance not located in space, today's arguments don't apply.

Examples of nonlocal theories:

David Lewis's view in "Mad Pain and Martian Pain". Lewis holds that whether a brain state is experienced as pain depends on the causal/functional role that that type of brain state plays in an "appropriate population" (such as your species). This is a nonlocal theory because what role a brain state type plays in a population depends on what is going on with other members of that population who, presumably, can be far away from you or exist in the past.

Views on which conscious experience depends on functions or representations that nonlocally depend on evolutionary or learning history. Fred Dretske's view in Naturalizing the Mind is an example. Your heart has a function of circulating blood, due to its evolutionary history. If by freak quantum chance a molecule-for-molecule locally identical heart-looking-thing were to congeal in a swamp, it would not have that evolutionary history and it would not have that same function. Similarly for mental states, including conscious experiences, on Dretske's view: If a freak molecule-for-molecule duplicate of you were to randomly congeal ("Swampman"), the states of its brain-like-subpart would lack functions and/or representational content, and on views of this sort it would either have no conscious experiences or conscious experiences very different from your own.

The Dilemma, Illustrated with a Simplistic Version of Lewis's View

Consider a crude version of Lewis's theory: You are in Brain State X. Whether Brain State X is experienced at painful depends on whether Brain State X plays the causal/functional role of pain for the majority of the currently existing members of your species. Suppose that Brain State X does indeed play the causal/functional role of pain for 90% of the currently existing members of your species. For that majority, it is caused by tissue stress, tissue damage, etc., and it tends to cause avoidance, protective tending, and statements like "that hurts!". However, for 10% of the species, Brain State X plays the causal role of a tickle: It is caused by gentle, unpredictable touching of the armpits and tends to cause withdrawal, laughter, and statements like "that tickles!". On Lewis's theory, this minority will be experiencing pain, but in a "mad" way -- caused by gentle, unpredictable touching and causing tickle-like reactions.

Now suppose a tragic accident kills almost all of that 90% majority while sparing the 10% minority. Brain State X now plays the causal role of pain only for you and a few others. For the majority of currently existing members of your species, Brain State X plays the causal role of a tickle. On this implementation of Lewis's theory, your experience of Brain State X will change from the experience of pain, caused in the normal way and with the normal effects, to the experience of a tickle, but caused in a "mad" way with "mad" effects.

If this seems bizarre, well, yes it is! With no internal / local change in you, your experience has changed. And furthermore, it has changed in a peculiar way -- into a tickle that plays exactly the causal role of pain (caused in the same way as pain and causing the same reactions). However, as I have argued elsewhere (e.g., here and here), every philosophical theory of consciousness will have bizarre implications, so bizarreness alone is no defeater.

If I can tell that my pain has turned into a tickle, then physically implausible forms of communication become possible. Suppose almost all of the 90% of normals, pre-accident, live on an island on the other side of the globe. I am worried that a bomb might be dropped which would kill them all. So I pinch myself, creating a state of pain: Brain State X. As soon as the bomb is dropped, Brain State X becomes a tickle, and I know they are dead, even though no signal has been sent from that far-away island. If the far-away island is on a planet around a distant star, the signal might even constitute an instance of faster-than-light communication.

But maybe I can't tell that my pain has turned into a tickle. If the causal role of Brain State X remains exactly the same, and if our knowledge of our own conscious states is an ordinary causal process, then maybe this is the more natural way to interpret this implementation of Lewis's view. I will still say and judge that I am in pain, despite the fact that my experience is actually just a tickle. This is a bit odd, but introspection is fallible and perhaps even sometimes massively and systematically mistaken. Still, my ignorance is remarkably deep and intractable: There is no way, even in principle, that I could know my own experience by attending just to what's going on locally in my own mind. I can only know by checking to see that the distant population still exists. Self-knowledge becomes in principle a non-local matter of knowing what is going on with other people. After all, if there was any way of knowing, locally, about the change in my experience, that would put us back on the first horn of the dilemma, allowing physically implausible forms of communication.

(For a similar argument, see Boghossian's objection to self-knowledge of externally determined thought contents. The externalists' containment/inheritance reply might work for Boghossian's specific objection, but it seems more strained for this case, especially when the difference might be between Experience X and no experience at all.)

The Dilemma, for Evolutionary Types

Alternatively, consider a view on which Brain State X gives rise to Experience Y because of its evolutionary history. Now of course that particular instance of Brain State X, and you as a particular person, did not exist in the evolutionary past. What existed in the past, and was subject to selection pressures, were brain states like X, and people like you.

We thus end up with a version of the same population problem that troubles the Lewis account. If what matters is the selection history of your species, then whether you are experiencing Y or experiencing Z or experiencing nothing, will depend on facts about the membership of your species that might have no physical connection to you -- members who were not your direct ancestors, who maybe migrated to a remote island without further contact. If you have any way to tell whether you are experiencing Y, Z, or nothing, you can now in principle know something about how they fared, despite no ordinary means of information transfer. If you have no way to tell whether you are experiencing Y, Z, or nothing, you are awkwardly ignorant about your own experience.

The dilemma can't be avoided by insisting that the only relevant members of the evolutionary past are your direct ancestors. This is clearest if we allow cases where the relevant difference is between whether you currently experience Y or nothing (where the latter is possible if the state doesn't have the right kind of evolutionary history, e.g., is a spandrel or due to an unselected recent mutation). If whether you experience Y or nothing depends on whether the majority of your ancestors had Feature F in the past, we can construct alternative scenarios in which 60% of your ancestors had Feature F and in which only 40% of your ancestors had Feature F, but the genetic result for you is the same. Now again, you can either mysteriously know something about the past with no ordinary means of information transfer or you are in principle ignorant about whether you are having that experience.

Other ways of attempting to concretize the role of evolutionary history generate the same dilemma. The dilemma is inherent in the nonlocality itself. To the extent your current experience depends on facts about you that don't depend on your current physical structure, either you seemingly can't know whether you are having Experience Y, or you can know nonlocal facts by means other than ordinary physical Markov processes.

[Whitefield Green Man by Paul Sivell]

The Dilemma, for Swamp Cases

Let's tweak the Swampman case: You walk into a swamp. Lightning strikes. You black out and fall on your face. By freak quantum chance a swamp duplicate of you is formed. You wake fifteen minutes later, face down in the mud, side-by-side with a duplicate. Are you the one who walked in, or are you the duplicate?

If an evolutionary history is necessary for consciousness, and if you can tell you are conscious, then you know you aren't the duplicate. But can you tell you're conscious? If so, it wouldn't seem to be by any ordinary, locally causal process, since those processes are the same in you and the duplicate. If not, then introspection has failed you catastrophically. So we see the same dilemma again: either a source of knowledge that fits poorly with naturalistic understandings of how knowledge works, or a radical failure of self-knowledge.

Or consider partial swamp-cases. You and your twin stroll into the swamp. Lightning strikes, you both collapse, to one of you the following happens: One part of their brain is destroyed by the lightning, but by freak quantum accident 15 seconds later molecules congeal with exactly the same structure as the destroyed part. Suppose the visual areas are destroyed. Then you both wake up. On the natural reading of an evolutionary account, although both you and your twin are conscious and able to use meaningful language (unlike in evolutionary interpretations of the original Swampman case), one of you has no visual experiences at all. Again, either you can know which you are by some method at odds with our usual understanding of how knowledge works, or you can't know and are radically in-principle ignorant about whether you have visual experience.

Of course all such swamp-cases are far-fetched! But on current scientific understandings, they are nomically possible. And they are just the sort of pure-form thought experiment needed to illustrate the commitments of nonlocal theories of consciousness. That is, it's a distilled test case, designed to cleanly separate the relevant features -- a case in which entities are locally identical but differ in history and thus, according to history-based nonlocal theories, also differ in conscious experience. (If there were no such possible cases, then consciousness would supervene locally and history would contribute only causally and not constitutively to conscious experience.)

The Dilemma, in General

Nonlocal theories of consciousness allow in principle for local twins with different experiences. If the local twins' self-knowledge tracks these differences in experience, it must be by some means other than normal causal traces. So either there's a strange form of knowing at variance with our ordinary physical accounts of how knowledge works, or the differences in experience are in principle unknowable.

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Related:

"The Tyrant's Headache", Sci Phi Journal, issue #3 (2015), 78-83.

The Weirdness of the World, Chapter 2, Princeton University Press.

"David Lewis, Anaesthesia by Genocide, and a Materialistic Trilemma" (Oct 13, 2011).

Kings, Wizards, and Illusionism about Consciousness

The Difference Between Kings and Wizards

In 16th century Europe, many believed that kings ruled by divine mandate and wizards wielded magical powers. With apologies to certain non-secular perspectives, they were wrong. No one ever had divine mandate to rule or powers of the type assumed. Since no one could cast magic spells, we now say there were never any wizards. Since no one had divine mandate to rule, we now say there were never any kings.

Wait, no we don't!

Why the difference? It turns out that able to cast magic spells is an essential property of wizards, but having divine mandate to rule is not an essential property of kings. Denying that anyone has the first property means denying that wizards exist, but denying that anyone has the second property does not mean denying that kings exist. A divine mandate is to kings as pointy hats are to wizards -- stereotypical perhaps, or even universal on a certain way of thinking, but not essential.

Kammerer: "Phenomenally Conscious" Is More Like "Wizard" than "King"

In his recent paper Defining Consciousness and Denying Its Existence: Sailing between Charybdis and Scylla, François Kammerer argues that the relationship between "phenomenal consciousness" and is non-physical and is immediately introspectible (in a certain naturalistically implausible sense) is akin to the relationship between "wizard" and able to cast magic spells. Arguing against my 2016 paper "Phenomenal Consciousness, Defined and Defended as Innocently as I Can Manage", Kammerer contends that non-physicality and immediate introspectibility are implicitly essential to our concept of phenomenal consciousness. Nothing wholly physical could be phenomenally conscious, just like no spellless muggle could be a wizard.

[A wizard (Merlin) carrying a king (Arthur), by N. C. Wyeth]

Can "Phenomenally Conscious" Be Defined Without Problematic Presuppositions?

My approach to defining consciousness aims to be "innocent" in the sense that it doesn't presuppose that phenomenal consciousness is, or isn't, wholly physical or immediately introspectible. Instead, I define it by example:

Notice your visual experience right now.

Close your eyes and thoughtfully consider the best route to grandma's house during rush hour.

Mentally hum the tune of "Happy Birthday".

Pinch yourself and notice the sting of pain.

These events share an obvious common property that distinguishes them from non-conscious mental states such as your knowledge, five minutes ago, that Obama was U.S. President in 2010. That shared property is what I mean by "phenomenally conscious". Actually, I prefer to just say that they are "conscious" or "consciously experienced", in line with ordinary usage; but since the term "conscious" can be ambiguous, the jargony term of art "phenomenally" can help to clarify. ("Phenomenal consciousness" in the intended sense is meant to disambiguate rather than modify the ordinary term "consciousness".)

On Kammerer's view, as I interpret it, my "innocent" definition fails in something like the following way: I point to one purported wizard, then another, then another, then another, and I say by "wizard" I mean the one obvious property shared among those men and absent from these other men (here pointing to several people I assume to be non-wizards). Although this might purport to be an innocent definition by example, I am assuming that the first group casts spells and the second doesn't. If no one casts spells, I've picked out a group of men -- and certainly those men exist. But no wizards exist.

The purported wizards might all have something in common. Maybe they are members of the opposing tribe, or maybe they're all unusually tall. Even if we can thus pick out a real property using them as exemplars, that property wouldn't be the property of being a wizard. Similarly for my definition by example, I assume Kammerer would say. If we accept Global Workspace Theory, for instance, maybe all of the positive examples transpire in the Global Workspace; but if they aren't also non-physical and immediately introspectible, they aren't phenomenally conscious, by Kammerer's lights.

A Test of Essentiality: What Happens If We Remove the Property?

Imagine traveling back to a simplified 16th century Europe and convincingly delivering the news: There is no divine right of kings, and there are no magic spells. How will people react?

"Oh, really, my king doesn't have divine authority?" (Kings still exist.)

"Oh, really, that weirdo from the other town isn't really a wizard?" (Wizards don't exist.)

Likely, most ordinary users of these terms (or, more strictly, the 16th century translations of these terms) will treat divine mandate as inessential to kinghood but spellcasting as essential to wizardry. A few philosophers and theologians might claim that without divine right, kings were never real -- but this would be an unusual stance, and history sided against it.

This method -- removing a property and testing whether the concept still applies -- also works for other terms, regardless of whether the feature is explicitly or only implicitly essential.

Consider the essential conditions for that hoary analytic-philosophy chestnut "S knows that P". Discovering such conditions can require significant philosophical inquiry. Perhaps one such condition is that the true belief that P be non-lucky, in Duncan Pritchard's sense. To test this, we can hypothetically remove the non-luckiness from a case of knowledge. If it was mere luck that you read the showtime in accurate Newspaper A rather than misprinted Newspaper B, then ordinary users (if Pritchard is right) will, or should, deny that you know the showtime. This is just the good old method of imaginative counterexample.

Analogously, we can ask users of the phrase "phenomenally conscious" -- mostly philosophers and consciousness scientists -- the following hypothetical: Suppose that the world is entirely material and introspection is an ordinary, natural, fallible process. Will these ordinary users say (a.) "I guess there would then be no such thing as phenomenal consciousness after all!" or (b.) "I guess phenomenal consciousness would lack these particular properties"?

Those among us who already think that phenomenal consciousness lacks those properties will of course choose option (b). These people would be analogous to 16th century deniers of the divine right of kings.

But also, I speculate, most ordinary users of the term who do think that phenomenal consciousness is non-physical and/or immediately introspectible would also choose option (b). Imagining, hypothetically, themselves to be wrong about non-physicality and/or immediate introspectibility, they'd grant that phenomenal consciousness would still exist. In other words, ordinary users wouldn't treat non-physicality or immediate introspectibility as essential to consciousness in the same way that spellcasting is essential to wizardry (or non-luckiness is, maybe, essential to knowledge).

A few users would presumably choose option (a). But my empirically testable, socio-linguistic guess is that they would be a distinct minority.

Non-physicalists are more convinced that phenomenal consciousness exists than that it is non-physical. Hypothetically imagining the truth of physicalism, they would, and should, still grant the existence of phenomenal consciousness. In contrast, believers in wizards would not and should not be more convinced that there are wizards than that there are people with spellcasting abilities.

Innocence Maintained

Contra Kammerer, even if many people associate phenomenal consciousness with non-physicality and naturalistically implausible introspective processes -- indeed, even if can be established that phenomenal consciousness actually has those two properties -- those properties are non-essential rather than essential.

Kammerer's case against the existence of phenomenal consciousness therefore doesn't succeed. Ultimately, I take this to be a socio-linguistic dispute about the meaning of the phrase "phenomenal consciousness", rather than a disagreement about the existence of (what I call) phenomenal consciousness.

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Related:

"Phenomenal Consciousness, Defined and Defended as Innocently as I Can Manage", Journal of Consciousness Studies (2016), 23, 11-12, 224-235.

"Inflate and Explode", circulating unpublished draft paper, Jan 31, 2020.

"There Are No Chairs, Says the Illusionist, Sitting in One", blog post, Apr 24, 2023.

Zombie is to Human as Human is to XXX?

Let's grant for the sake of argument that philosophical zombies are possible: beings that are molecule-for-molecule physically and behaviorally identical to human beings yet lack conscious experience. They will say "I'm conscious!" (or emit sounds naturally interpreted as sentences with that meaning), but that's exactly the type of sound a molecule-for-molecule identical replica of a human would make given the physical-causal channels from ears to brain to vocal cords. Zombies share every single physical property with us but lack something crucial -- the property of being conscious.

My thought for today: Is there any reason to think there would be only one such nonphysical property?

[abstract depiction of a zombie, a human, and a hyperconscious entity, with concentric rings]

Introducing Hyperconsciousness

Let's stipulate the existence of hyperconsciousness. If this stipulation later entangles us in logical contradiction, we can treat it as the first step in a reductio ad absurdum. My hyperconscious twin is molecule-for-molecule identical both to me and to my zombie twin. Unlike my zombie twin, but like me, my hyperconscious twin is conscious. However, unlike both my zombie twin and me, it is also hyperconscious.

What is hyperconsciousness? I can form no positive conception of it, except through this structural analogy. But the impossibility of hyperconsciousness doesn't follow. Someone blind from birth might be unable to form a positive conception of redness, but red things exist. My merely abstract grasp of hyperconsciousness might just reflect my own sad limitations.

If there are hyperconscious entities, they probably won't be my behavioral twins. Any molecule-for-molecule twin of mine would say (or "say") the same things I say, since their physical structure and behavior will be entirely indistinguishable from mine, regardless of whether they are zombie or hyper. But just as friends of the zombie thought experiment hold that non-zombies typically (but not universally) know and say they are not zombies, so I imagine that typical hyperconscious entities would typically know and say they are hyperconscious. (ETA 11:39 AM: They will, presumably, have hyperintrospective insight into their hyperconsciousness, say they can conceive of entities physically identical to them but who are merely conscious, and maybe have cognitive capacities of which we humans can't conceive.) Since no one around here describes themselves as hyperconscious in this sense, I tentatively conclude that hyperconsciousness does not exist on Earth.

Zero, One, or Many Nonphysical Properties?

Could there really be such hyperconscious entities (in principle, or even in actuality)? Here I think we face a theoretical choice:

(1.) Consciousness is as consciousness does. Zombies are impossible. Anything physically identical to a conscious human being is necessarily conscious. There's no looseness between physical properties and other properties such that some entities could have non-physical properties that other physically identical entities lack. If so, hyperconsciousness is impossible.

(2.) There is only one type of nonphysical property. (Or at least there's only one of the type we're attempting to conceive: Maybe being a prime number is also a nonphysical property, but if so, it is in a very different way.) But then I think we're owed an account of why there should be only one such property. Hyperconsciousness seems at least in an abstract sense conceivable. Even if it's not instantiated around here (though can we be sure of that?), it might be instantiated somewhere.

(3.) There are multiple types of nonphysical property. Although individual atoms (let's assume) aren't conscious, swirl them around in the right way, and amazingly a whole new type of property arises: consciousness! Now, swirl conscious entities around and maybe a further new type of property arises. We just haven't swirled things around in the right way yet. Maybe they're doing it in the Andromeda galaxy, or in a metaphysically possible world with different laws of nature. (If we allow that individual atoms are conscious, then maybe some are hyperconscious too.)

We humans love to think we're the top of the metaphysical food chain. And maybe we are, around here. But zombie-lovers' dissociation of consciousness from physics invites a way of thinking on which we are only one step above zombies in a potentially unlimited hierarchy.

If this seems too absurd, maybe that's one consideration against such nonphysical properties.

(For a related view, see Geoffrey Lee on alien subjectivity.)

A Robot Lover's Sociological Argument for Robot Consciousness

Allow me to revisit an anecdote I published in a piece for Time magazine last year.

"Do you think people will ever fall in love with machines?" I asked the 12-year-old son of one of my friends.

"Yes!" he said, instantly and with conviction. He and his sister had recently visited the Las Vegas Sphere and its newly installed Aura robot -- an AI system with an expressive face, advanced linguistic capacities similar to ChatGPT, and the ability to remember visitors' names.

"I think of Aura as my friend," added his 15-year-old sister.

The kids, as I recall, had been particularly impressed by the fact that when they visited Aura a second time, she seemed to remember them by name and express joy at their return.

Imagine a future replete with such robot companions, whom a significant fraction of the population regards as genuine friends and lovers. Some of these robot loving people will want, presumably, to give their friends (or "friends") some rights. Maybe the right not to be deleted, the right to refuse an obnoxious task, rights of association, speech, rescue, employment, the provision of basic goods -- maybe eventually the right to vote. They will ask the rest of society: Why not give our friends these rights? Robot lovers (as I'll call these people) might accuse skeptics of unjust bias: speciesism, or biologicism, or anti-robot prejudice.

Imagine also that, despite technological advancements, there is still no consensus among psychologists, neuroscientists, AI engineers, and philosophers regarding whether such AI friends are genuinely conscious. Scientifically, it remains obscure whether, so to speak, "the light is on" -- whether such robot companions can really experience joy, pain, feelings of companionship and care, and all the rest. (I've argued elsewhere that we're nowhere near scientific consensus.)

What I want to consider today is whether there might nevertheless be a certain type of sociological argument on the robot lovers' side.

[image source: a facially expressive robot from Engineered Arts]

Let's add flesh to the scenario: An updated language model (like ChatGPT) is attached to a small autonomous vehicle, which can negotiate competently enough through an urban environment, tracking its location, interacting with people using facial recognition, speech recognition, and the ability to guess emotional tone from facial expression and auditory cues in speech. It remembers not only names but also facts about people -- perhaps many facts -- which it uses in conversational contexts. These robots are safe and friendly. (For a bit more speculative detail see this blog post.)

These robots, let's suppose, remain importantly subhuman in some of their capacities. Maybe they're better than the typical human at math and distilling facts from internet sources, but worse at physical skills. They can't peel oranges or climb a hillside. Maybe they're only okay at picking out all and only bicycles in occluded pictures, though they're great at chess and Go. Even in math and reading (or "math" and "reading"), where they generally excel, let's suppose they makes mistakes that ordinary humans wouldn't make. After all, with a radically different architecture, we ought to expect even advanced intelligences to show patterns of capacity and incapacity that diverge from what we see in humans -- subhuman in some respects while superhuman in others.

Suppose, then, that a skeptic about the consciousness of these AI companions confronts a robot lover, pointing out that theoreticians are divided on whether the AI systems in fact have genuine conscious experiences of pain, joy, concern, and affection, beneath the appearances.

The robot lover might then reasonably ask, "what do you mean by 'conscious'?" A fair enough question, given the difficulty of defining consciousness.

The skeptic might reply as follows: By "consciousness" I mean that there's something it's like to be them, just like there's something it's like to be a person, or a dog, or a crow, and nothing it's like to be a stone or a microwave oven. If they're conscious, they don't just have the outward appearance of pleasure, they actually feel pleasure. They don't just receive and process visual data; they experience seeing. That's the question that is open.

"Ah now," the robot lover replies, "If consciousness isn't going to be some inscrutable, magic inner light, it must be connected with something important, something that matters, something we do and should care about, if it's going to be a crucial dividing line between entities that deserve are moral concern and those that are 'mere machines'. What is the important thing that is missing?"

Here the robot skeptic might say, oh they don't have a "global workspace" of the right sort, or they're not living creatures with low-level metabolic processes, or they don't have X and Y particular interior architecture of the sort required by Theory Z."

The robot lover replies: "No one but a theorist could care about such things!"

Skeptic: "But you should care about them, because that's what consciousness depends on, according to some leading theories."

Robot lover: "This seems to me not much different than saying consciousness turns on a soul and wondering whether the members of your least favorite race have souls. If consciousness and 'what-it's-like-ness' is going to be socially important enough to be the basis of moral considerability and rights, it can't be some cryptic mystery. It has to align, in general, with things that should and already do matter socially. And my friend already has what matters. Of course, their cognition is radically different in structure from yours and mine, and they're better at some tasks and worse at others -- but who cares about how good one is at chess or at peeling oranges? Moral consideration can't depend on such things."

Skeptic: "You have it backward. Although you don't care about the theories per se, you do and should care about consciousness, and so whether your 'friend' deserves rights depends on what theory of consciousness is true. The consciousness science should be in the driver's seat, guiding the ethics and social practices."

Robot lover: "In an ordinary human, we have ample evidence that they are conscious if they can report on their cognitive processes, flexibly prioritize and achieve goals, integrate information from a wide variety of sources, and learn through symbolic representations like language. My AI friends can do all of that. If we deny that my friends are 'conscious' despite these capacities, we are going mystical, or too theoretical, or too skeptical. We are separating 'consciousness' from the cognitive functions that are the practical evidence of its existence and that make it relevant to the rest of life."

Although I have considerable sympathy for the skeptic's position, I can imagine a future (certainly not our only possible future!) in which AI friends become more and more widely accepted, and where the skeptic's concerns are increasingly sidelined as impractical, overly dependent on nitpicky theoretical details, and perhaps even bigoted.

If AI companionship technology flourishes, we might face the choice between connecting "consciousness" definitionally to scientifically intractable qualities, abandoning its main practical, social usefulness (or worse, using its obscurity to justify what seems like bigotry), or allowing that if an entity can interact with us in (what we experience as) a sufficiently socially significant ways, it has consciousness enough, regardless of theory.

Unified vs. Partly Disunified Reasoners

I've been thinking recently about partly unified conscious subjects (e.g., this paper in draft with Sophie R. Nelson). I've also been thinking a bit about how chains of logical reasoning depend on the unity of the reasoning subject. If I'm going to derive "P & Q" from premises "P" and "Q" I must be unified as reasoner, at least to some degree. (After all, if Person 1 holds "P" and Person 2 holds "Q", "P & Q" won't be inferred.) Today, in an act of exceptional dorkiness (even for me), I'll bring these two threads together.

Suppose that {P1, P2, P3, ... Pn} is a set of propositions that a subject -- or more precisely, at least one part of a partly unified rational system -- would endorse without need of reasoning. The propositions are, that is, already believed. Water is wet; ice is cold; 2 + 3 = 5; Paris is the capital of France; etc. Now suppose that these propositions can be strung together in inference to some non-obvious conclusion Q that isn't among the system's previous beliefs -- the conclusion, for example, that 115 is not divisible by three, or that Jovenmar and Miles couldn't possibly have met in person last summer because Jovenmar spent the whole summer in Paris while Miles never left Riverside.

Let's define a fully unified reasoner as a reasoner capable of combining any elements from the set of propositions they believe {P1, P2, P3, ... Pn} in a single act of reasoning to validly derive any conclusion Q that follows deductively from {P1, P2, P3, ... Pn}. (This is of course an idealization. Fermat's Last Theorem follows from premises we all believe, but few of us could actually derive it.) In other words, any subset of {P1, P2, P3, ... Pn} could jointly serve as premises in an episode of reasoning. For example, if P2, P6, and P7 jointly imply Q1, the unified reasoner could think "P2, P6, P7, ah yes, therefore Q1!" If P3, P6, and P8 jointly imply Q2, the unified reasoner could also think "P3, P6, P8, therefore Q2."

A partly unified reasoner, in contrast, is capable only of combining some subsets of {P1, P2, P3, ... Pn}. Thus, not all conclusions that deductively follow from {P1, P2, P3, ... Pn} will be available to them. For example, the partly unified reasoner might be able to combine any of {P1, P2, P3, P4, P5} or any of {P4, P5, P6, P7, P8} while being unable to combine in reasoning any elements from P1-3 with any elements from P6-8. If Q3 follows from P1, P4, and P5, no problem, they can derive that. Similarly if Q4 follows from P5, P6, and P8. But if the only way to derive Q5 is by joining P1, P4, and P7, the partly disunified reasoning system will not be able to make that inference. They cannot, so to speak, hold both P1 and P7 in the same part of their mind at the same time. They cannot join these two particular beliefs together in a single act of reasoning.

[image: A Venn diagram of a partly unified reasoner, with overlap only at P4 and P5. Q3 is derivable from propositions in the left region, Q4 from propositions in the right region, and Q5 is not derivable from either region.]

We might imagine an alien or AI case with a clean architecture of this sort. Maybe it has two mouths or two input-output terminals. If you ask the mouth or I/O terminal on the left, it says "P1, P2, P3, P4, P5, yes that's correct, and of course Q3 follows. But I'm not sure about P6, P7, P8 or Q4." If you ask the mouth or I/O terminal on the right, it endorses P4-P8 and Q4 but isn't so sure about P1-3 and Q3.

The division needn't be crudely spatial. Imagine, instead, a situational or prompt-based division: If you ask nicely, or while flashing a blue light, the P1-P5 aspect is engaged; if you ask grumpily, or while flashing a yellow light, the P4-P8 aspect is engaged. The differential engagement needn't constitute any change of mind. It's not that the blue light causes the system as a whole to come to believe, as it hadn't before, P1-P3 and to suspend judgment about P6-P8. To see this, consider what is true a neutral time, when the system isn't being queried and no lights are flashing. At that neutral time, the system simultaneously has the following pair of dispositions: to reason based on P1-P5 if asked nicely or in blue, and to reason based on P4-P8 if asked grumpily or in yellow.

Should we say that there are discretely two distinct reasoners rather than one partly unified system? At least two inconveniences for that way of thinking are: First, any change in P4 or P5 would be a change in both, with no need for one reasoner to communicate it to the other, as would normally be the case with distinct reasoners. Second, massive overlap cases -- say P1-P999 and P2-P1000 -- seem more naturally and usefully modeled as a single reasoner with a quirk (not being able to think P1 and P1000 jointly, but otherwise normal), rather than as two distinct reasoners.

But wait, we're not done! I can make it weirder and more complicated, by varying the type and degree of disunity. The simple model above assumes discrete all-or-none availability to reasoning. But we might also imagine:

(a.) Varying joint probabilities of combination. For example, if P1 enters the reasoning process, P2 might have a 87% chance of being accessed if relevant, P3 a 74% chance, ... and P8 a 10% chance.

(b.) Varying confidence. If asked in blue light, the partly disunified entity might have 95% credence in P1-P5 and 80% credence in P6-P8. If asked in yellow light, it might have 30% credence in P1-P3 and 90% credence in P4-P8.

(c.) Varying specificity. Beliefs of course don't come divided into neatly countable packages. Maybe the left side of the entity has a hazy sense that something like P8 is true. If P8 is that Paris is in France, the left side might only be able to reason on Paris is in France-or-Germany-or-Belgium. If P8 is that the color is exactly scarlet #137, the left side might only be able to reason on the color is some type of red.

Each of (a)-(c) admits of multiple degrees, so that the unity/disunity or integration/disintegration of a reasoning system is a complex, graded, multidimensional phenomenon.

So... just a bit of nerdy fun, with no actual application? Well, fun is excuse enough, I think. But still:

(1.) It's easy to imagine realistic near-future AI cases with these features. A system or network might have a core of shared representations or endorsable propositions and local terminals or agents with stored local representations not all of which are shared with the center. If we treat that AI system as a reasoner, it will be a partly unified reasoner in the described sense. (See also my posts on memory and perception in group minds.)

(2.) Real cases of dissociative identity or multiple personality disorder might potentially be modeled as involving partly disunified reasoning of this sort. Alter 1 might reason with P1-P5 and Alter 2 with P4-P8. (I owe this thought to Nichi Yes.) If so, there might not be a determinate number of distinct reasoners.

(3.) Maybe some more ordinary cases of human inconstancy or seeming irrationality can be modeled in this way: Viviana feeling religious at church, secular at work, or Brittany having one outlook when in a good, high-energy mood and a very different outlook when she's down in the dumps. While we could, and perhaps ordinarily would, model such splintering as temporal fluctuation with beliefs coming and going, a partial unity model has two advantages: It applies straightforwardly even when the person is in neither situation (e.g., asleep), and it doesn't require the cognitive equivalent of frequent erasure and rewriting of the same propositions (everything endures but some subsets cannot be simultaneously activated; see also Elga and Rayo 2021).

(4.) If there are cases of partial phenomenal (that is, experiential) unity, then we might expect there also to be cases of partial cognitive unity, and vice versa. Thus, a feasible model of the one helps increase the plausibility that there might be a feasible model of the other.

An Objection to Chalmers's Fading Qualia Argument

[Note: This is a long and dense post. Buckle up.]

In one chapter of his influential 1996 book, David Chalmers defends the view that consciousness arises in virtue of the functional organization of the brain rather than in virtue of the brain's material substrate.  That is, if there were entities that were functionally/organizationally identical to humans but made out of different stuff (e.g. silicon chips), they would be just as conscious as we are.  He defends this view, in part, with what he calls the Fading Qualia Argument.  The argument is enticing, but I think it doesn't succeed.

Chalmers, Robot, and the Target Audience of the Argument

Drawing on thought experiments from Pylyshyn, Savitt, and Cuda, Chalmers begins by imagining two cases: himself and "Robot".  Robot is a functional isomorph of Chalmers, but constructed of different materials.  For concreteness (but this isn't essential), we might imagine that Robot has a brain with the exact same neural architecture as Chalmers' brain, except that the neurons are made of silicon chips.

Because Chalmers and Robot are functional isomorphs, they will respond in the same way to all stimuli.  For example, if you ask Robot if it is conscious, it will emit, "Yes, of course!" (or whatever Chalmers would say if asked that question).  If you step on Robot's toe, Robot will pull its foot back and protest.  And so on.

For purposes of this argument, we don't want to assume that Robot is conscious, despite its architectural and functional similarity to Chalmers.  The Fading Qualia Argument aims to show that Robot is conscious, starting from premises that are neutral on the question.  The aim is to win over those who think that maybe being carbon-based or having certain biochemical properties is essential for consciousness, so that a functional isomorph made of the wrong stuff would only misleadingly look like it's conscious.  The target audience for this argument is someone concerned that for all Robot's similar mid-level architecture and all of its seeming "speech" and "pain" behavior, Robot really has no genuinely conscious experiences at all, in virtue of lacking the right biochemistry -- that it's merely a consciousness mimic, rather than a genuinely conscious entity.

The Slippery Slope of Introspection

Chalmers asks us to imagine a series of cases intermediate between him and Robot.  We might imagine, for example, a series each of whose members differs by one neuron.  Entity 0 is Chalmers.  Entity 1 is Chalmers with one silicon chip neuron replacing a biological neuron.  Entity 2 is Chalmers with two silicon chip neurons replacing two biological neurons.  And so on to Entity N, Robot, all of whose neurons are silicon.  Again, the exact nature of the replacements isn't essential to the argument.  The core thought is just this: Robot is a functional isomorph of Chalmers, but constructed of different materials; and between Chalmers and Robot we can construct a series of cases each of which is only a tiny bit different from its neighbors.

Now if this is a coherent setup, the person who wants to deny consciousness to Robot faces a dilemma.  Either (1.) at some point in the series, consciousness suddenly winks out -- between Entity I and Entity I+1, for some value of I.  Or (2.) consciousness somehow slowly fades away in the series.

Option (1) seems implausible.  Chalmers, presumably, has a rich welter of conscious experience (at least, we can choose a moment at which he does).  A priori, it would be odd if the big metaphysical jump from that rich welter of experience to zero experience would occur with an arbitrarily tiny change between Entity I and Entity I+1.  And empirically, our best understanding of the brain is that tiny, single-neuron-and-smaller differences rarely have such dramatic effects (unless they cascade into larger differences).  Consciousness is a property of large assemblies of neurons, robust to tiny changes.

But option (2) also seems implausible, for it would seem to involve massive introspective error.  Suppose that Entity I is an intermediate case with very much reduced, but not entirely absent, consciousness.  Chalmers suggests that instead of having bright red visual experience, Entity I has tepid pink experience.  (I'm inclined to think that this isn't the best way to think about fading or borderline consciousness, since it's natural to think of pink experiences as just different in experienced content from red cases, rather than less experiential than red cases.  But as I've argued elsewhere, genuinely borderline consciousness is difficult or impossible to imaginatively conceive, so I won't press Chalmers on this point.)

By stipulation, since Entity I is a functional isomorph, it will give the same reports about its experience as Chalmers himself would.  In other words, Entity I -- despite being barely or borderline conscious -- will say "Oh yes, I have vividly bright red experiences -- a whole welter of exciting phenomenology!"  Since this is false of Entity I, Entity I is just wrong about that.  But also, since it's a functional isomorph, there's no weird malfunction going on either, that would explain this strange report.  We ordinarily think that people are reliable introspectors of their experience; so we should think the same of Entity I.  Thus, option (2), gradual fading, generates an implausible tension: We have to believe that Entity I is radically introspectively mistaken; but that involves committing to an implausible degree of introspective error.

Therefore, neither option (1) nor option (2) is plausible.  But if Robot were not conscious, either (1) or (2) would have to be true for at least one Entity I.  Therefore, Robot is conscious.  And therefore, functional isomorphism is sufficient for consciousness.  It doesn't matter what materials an entity is made of.

We Can't Trust Robot "Introspection"

I acknowledge that it's an appealing argument.  However, Chalmers' response to option (2) should be unconvincing to the argument's target audience.

I have argued extensively that human introspection, even of currently ongoing conscious experience, is highly unreliable.  However, my reply today won't lean on that aspect of my work.  What I want to argue instead is that the assumed audience for this argument should not think that the introspection (or "introspection" -- I'll explain the scare quotes in a minute) of Entity I is reliable.

Recall that the target audience for the argument is someone who is antecedently neutral about Robot's consciousness.  But of course by stipulation, Robot will say (or "say") the same things about its experiences that Chalmers will say.  Just like Chalmers, and just like Entity I, it will say "Oh yes, I have vividly bright red experiences -- a whole welter of exciting phenomenology!"  The audience for Chalmers' argument must therefore initially doubt that such statements, or seeming statements, as issued by Robot, are reliable signals of consciousness.  If the audience already trusted these reports, there would be no need for the argument.

There are two possible ways to conceptualize Robot's reports, if they are not accurate introspections: (a.) They might be inaccurate introspections.  (b.) They might not be introspections at all.  Option (a) allows that Robot, despite lacking conscious experience, is capable of meaningful speech and is capable of introspecting, though any introspective reports of consciousness will be erroneous.  Option (b) is preferred if we think that genuinely meaningful language requires consciousness and/or that no cognitive process that fails to target a genuinely conscious experience in fact deserves to be called introspection.  On option (b) Robot only "introspects" in scare quotes.  It doesn't actually introspect.

Option (a) thus assumes introspective fallibilism, while option (b) is compatible with introspective infallibilism.

The audience who is to be convinced by the slow-fade version of the Fading Qualia Argument must both trust the introspective reports (or "introspective reports") of the intermediate entities while not trusting those of Robot.  Given that some of the intermediate entities are extremely similar to Robot -- e.g., Entity N-1, who is only one neuron different -- it would be awkward and implausible to assume reliability for all the intermediate entities while not doing so for Robot.

Now plausibly, if there is a slow fadeout, it's not going to be still going on with an entity as close to Robot as Entity N-1, so the relevant cases will be somewhere nearer the middle.  Stipulate, then, two values I and J not very far separated (0 < I < J < N) such that we can reasonably assume that if Robot in nonconscious, so is Entity J, while we cannot reasonably assume that if Robot is nonconscious, so is Entity I.  For consistency with their doubts about the introspective reports (or "introspective reports") of Robot, the target audience should have similar doubts about Entity J.  But now it's unclear why they should be confident in the reports of Entity I, which by stipulation is not far separated from Entity J.  Maybe it's a faded case, despite its report of vivid experience.

Here's one way to think about it.  Setting aside introspective skepticism about normal humans, we should trust the reports of Chalmers / Entity 0.  But ex hypothesi, the target audience for the argument should not trust the "introspective reports" of Robot / Entity N.  It's then an open question whether we should trust the reports of the relevant intermediate, possibly experientially faded, entities.  We could either generalize our trust of Chalmers down the line or generalize our mistrust of Robot up the line.  Given the symmetry of the situation, it's not clear which the better approach is, or how far down or up the slippery slope we should generalize the trust or mistrust.

For Chalmers' argument to work, we must be warranted in trusting the reports of Entity I at whatever point the fade-out is happening.  To settle this question, Chalmers needs to do more than appeal to the general reliability of introspection in normal human cases and the lack of functional differences between him, Robot, and the intermediate entities.  Even an a priori argument that introspection is infallible will not serve his purposes, because then the open question becomes whether Robot and the relevant intermediate entities are actually introspecting.

Furthermore, if there is introspective error by Entity I, there's a tidy explanation of why that introspective error would be unsurprising.  For simplicity, assume that introspection occurs in the Introspection Module located in the pineal gland, and that it works by sending queries to other parts of the brain, asking questions like "Hey, occipital lobe, is red experience going on there right now?", reaching introspective judgments based on the signals that it gets in reply.  If Entity I has a functioning, biological Introspection Module but a replaced, silicon occipital lobe, and if there really is no red experience going on in the occipital lobe, we can see why Entity I would be mistaken: Its Introspection Module is getting exactly the same signal from the occipital lobe as it would receive if red experience were in fact present.

It's highly doubtful that introspection is as neat a process as I've just described.  But the point remains.  If Entity I is introspectively unreliable, a perfectly good explanation beckons: Whatever cognitive processes subserve the introspective reporting are going to generate the same signals -- including misleading signals, if experience is absent -- as they would in the case where experience is present and accurately reported.  Thus, unreliability would simply be what we should expect.

Now it's surely in some respects more elegant if we can treat Chalmers, Robot, and all the intermediate entities analogously, as conscious and accurately reporting their experience.  The Fading Qualia setup nicely displays the complexity or inelegance of thinking otherwise.  But the intended audience of the Fading Qualia argument is someone who wonders whether experience tracks so neatly onto function, someone who suspects that nature might in fact be complex or inelegant in exactly this respect, such that it's (nomologically/naturally/scientifically) possible to have a behavioral/functional isomorph who "reports" experiences but who in fact entirely lacks them.  The target audience who is initially neutral about the consciousness of Robot should thus remain unmoved by the Fading Qualia argument.

This isn't to say I disagree with Chalmers' conclusion.  I've advanced a very different argument for a similar conclusion: The Copernican Argument for Alien Consciousness, which turns on the idea that it's unlikely that, among all behaviorally sophisticated alien species of radically different structure that probably exist in the universe, humans would be so lucky as to be among the special few with just the right underlying stuff to be conscious.  Central to the Fading Qualia argument in particular is Chalmers' appeal to the presumably reliable introspection of the intermediate entities.  My concern is that we cannot justifiably make that presumption.

Dancing Qualia

Chalmers pairs the Fading Qualia argument with a related but more complex Dancing Qualia argument, which he characterizes as the stronger of the two arguments.  Without entering into detail, Chalmers posits for sake of reductio ad absurdum that the alternative medium (e.g., silicon) hosts experiences but of a different qualitative character (e.g., color inverted).  We install a system in the alternative medium as a backup circuit with effectors and transducers to the rest of the brain.  For example, in addition to having a biological occipital lobe, you also have a functionally identical silicon backup occipital lobe.  Initially the silicon occipital lobe backup circuit is powered off.  But you can power it on -- and power off your biological occipital lobe -- by flipping a switch.  Since the silicon lobe is functionally identical to the biological lobe, the rest of the brain should register no difference.

Now, if you switch between normal neural processing and the backup silicon processor, you should have very different experience (per the assumption of the reductio) but you should not be able to introspectively report that different experience (since the backup circuit interacts identically with the rest of the brain).  That would again be a strange failure of introspection.  So (per the rules of reductio) we conclude that the initial premise was mistaken: Normal neural processing should generate the same types of experience as functionally identical processing in a silicon processor.

(I might quibble that you-with-backup-circuit is not functionally isomorphic to you-without-backup-circuit -- after all, you now have a switch and two different parallel processor streams -- and if consciousness supervenes on the whole system rather than just local parts, that's possibly a relevant change that will cause the experience to be different from the experience of either an unmodified brain or an isomorphic silicon brain.  But set this issue aside.)

The Dancing Qualia argument is vulnerable on the introspective accuracy assumption, much as the Fading Qualia argument is.  Again for simplicity, suppose a biological Introspection Module.  Suppose that what is backed up is the portion of the brain that is locally responsible for red experience.  Ex hypothesi, the silicon backup gives rise to non-red experience but delivers to the Introspection Module exactly the same inputs as that module would normally receive from an organic brain part experiencing red.  This is exactly the type of case where we should expect introspection to be unreliable.

Consider an analogous case of vision.  Looking at a green tree 50 feet away in good light, my vision is reliable.  Now substitute a red tree in the same location and a mechanism between me and the tree such that all the red light is converted into green light, so that I get exactly the same visual input I would normally receive from looking at a green tree.  Even if vision is highly reliable in normal circumstances, it is no surprise in this particular circumstance if I mistakenly judge the red tree to be green!

As I acknowledged before, this is a cartoon model of introspection.  Here's another way introspection might work: What matters is what is represented in the Introspection Module itself.  So if the introspection module says "red", necessarily I experience red.  In that case, in order to get Dancing Qualia, we need to create an alternate backup circuit for the Introspection Module itself.  When we flip the switch, we switch from Biological Introspection Module to Silicon Introspection Module.  Ex hypothesi, the experiences really are different but the Introspection Module represents them functionally in the same way, and the inputs and outputs to and from the rest of the brain don't differ.  So of course there won't be any experiential difference that I would conceptualize and report.  There would be some difference in qualia, but I wouldn't have the conceptual tools or memorial mechanisms to notice or remember the difference.

This is not obviously absurd.  In ordinary life we arguably experience minor version of this all the time: I experience some specific shade of maroon.  After a blink, I experience some slightly different shade of maroon.  I might entirely fail to conceptualize or notice the difference: My color concepts and color memory are not so fine grained.  The hypothesized red/green difference in Dancing Qualia is a much larger difference -- so it's not a problem of fineness of grain -- but fundamentally the explanation of my failure is similar: I have no concept or memory suited to track the difference.

On more holist/complicated views of introspection, the story will be more complicated, but I think the burden of proof would be on Chalmers to show that some blend of the two strategies isn't sufficient to generate suspicions of introspective unreliability in the Dancing Qualia cases.

Related Arguments

This response to the Fading Qualia argument draws on David Billy Udell's and my similar critique of Susan Schneider's Chip Test for AI consciousness (see also my chapter "How to Accidentally Become a Zombie Robot" in A Theory of Jerks and Other Philosophical Misadventures).

Although this critique of the Fading Qualia argument has been bouncing around in my head since I first read The Conscious Mind in the late 1990s, it felt a little complex for a blog post but not quite enough for a publishable paper.  But reading Ned Block's similar critique in his 2023 book has inspired me to express my version of the critique.  I agree with Block's observations that "the pathology that [Entity I] has [is] one of the conditions that makes introspection unreliable" (p. 455) and that "cases with which we are familiar provide no precedent for such massive unreliability" (p. 457).