James Stanley

Consciousness is computable

Mon 20 June 2022
Tagged: philosophy

At first I thought it was quite surprising that consciousness can exist in the first place. It doesn't seem to be the same sort of thing as anything else that exists. But there's an enormous selection bias here: every possible universe in which consciousness can not exist does not contain anybody wondering why it doesn't exist. The only time you can even ask the question is when it already exists. So in that sense it's not at all surprising that consciousness exists, it is in fact guaranteed!

And Matt pointed out that the universe actually contains many surprising things. Electricity, magnetism, gravity, fire, light, planets, trees, boats, computers, and so on. These are all very strange and surprising things that you probably couldn't imagine if you didn't already know about them, and yet they exist in our universe with no trouble at all. Why should consciousness be any different? And yet consciousness does feel different. All of the other things happen, apparently, completely mechanically, even if the mechanisms are complicated. But consciousness has a mind of its own.

What do I mean by consciousness?

By "consciousness" I don't mean other related things like emotions, feelings, intelligence, or decision-making. I think those things can be explained without any "observer".

I struggle to put into words exactly what I do mean, but I think it should be obvious to anyone who is actually conscious. I am aware that I exist. I think therefore I am. I have an internal experience, in which I am the subject of things that happen to me.

Sometimes when I talk to people about consciousness they try to argue that it is an illusion, and that we're all tricked into thinking we're conscious when we're actually not. I find this position self-contradictory. Consciousness isn't the illusion, consciousness is the audience. Anyone who has ever been conscious knows that being conscious is different to not being conscious.

Arguing that there's no such thing as consciousness is like arguing that there's no such thing as hunger. "Oh, people just say they're hungry when they haven't eaten lately, but nobody actually feels hungry". But if you've ever felt hungry in your life then you know that this is false. The same with consciousness: the only way you could seriously believe that consciousness is an illusion is if you have never experienced it.

And that is a distinct possibility! A p-zombie is a hypothetical person who looks and acts and seems just like an ordinary person, except they have no consciousness. There is no internal experience. There is no awareness. A p-zombie takes the same sorts of inputs as a conscious human, and produces the same sorts of outputs, and for all intents and purposes appears conscious, but is actually not, and there is no way to tell from the outside.

It is entirely possible that some (or many, or most!) of the people in the world are p-zombies. Solipsism holds that everyone in the world is a p-zombie, apart from me.

It might sound egotistical to imagine that I may be the only truly conscious being ever to exist, but I don't think it's that far outside the realms of possibility. After all, I can hear my thoughts and I can't hear yours.

Personally I prefer to live in a world in which other people are real than one in which they are not, so I discount Solipsism out of hand. Even if I am the only truly conscious being in the universe, I think I get more out of it by pretending the NPCs are real.

What do I mean by computable?

I thought this was a pretty settled question, with an answer something like "able to be calculated by a Turing machine", but it turns out there is a field of hypercomputation which studies computational models stronger than that of a Turing machine.

But by "computable", I mean "able to be calculated by a Turing machine". For consciousness to be computable, I mean that it is possible for a Turing machine to create consciousness.

I don't merely mean that it is possible to create a convincing simulation of a consciousness that gives plausible outputs for any given inputs. That would be a p-zombie. Anyone who is conscious knows there is more to consciousness than just saying you're conscious.


Premise 1: Everything in the universe is explained by the laws of physics.

By "laws of physics", I mean the complete set of laws that govern the universe. This premise seems almost tautological.

I think the only way it might be disputed would be if you argue that there is no set of laws governing the universe, and literally everything can happen, and does happen, and no laws apply. That the only reason we seem to have laws on a macro scale is some sort of constructive interference between all the different ways the universe can do everything all at once.

Premise 2: Physics is computable.

I'm not sure how to argue this one. Classical physics is computable. Relativity is computable. Quantum mechanics is computable (even without quantum computing) for whatever finite degree of precision you want. What would non-computable physical laws even look like?

Premise 3: Consciousness exists within the universe.

The best arguments I know of in favour of this premise are:

Alternatively, it could be that the universe is more like the world in a video game, except the player of the game has their senses hooked up directly to the game at birth, so that they have no way to receive sensory input from anything outside the game universe. As far as such a player would be concerned, the video game is all that exists. They would be just as baffled as we are about how consciousness can arise in such a primitive world.

You could even imagine that anaesthetics exist within the game, except whenever the player in the game receives anaesthetic, the "real life" player is also injected with anaesthetic (by a robot or diligent minder), such that it appears to the player that the anaesthetic within the game is fully functional. Arguably it is.

The "video game universe" idea doesn't even require you to assume that everyone else is a p-zombie. Multiplayer games exist.

Conclusion: Consciousness is computable.

If you accept all 3 premises, then I think you have to accept the conclusion. However, the conclusion is obviously absurd. It seems obvious to me that no amount of computing can create the sensation of existing as a mind.

So I think this suggests that one of the premises is false, which also seems surprising, but maybe not quite so much? At least there are 3 times as many places for the surprising part to be hiding.

Either minds have something that computers don't, or they don't. Neither possibility seems correct.

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