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.

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.