The Scientific Method part 5: Illusions, Delusions, and Dreams

(This is the fifth in a series on the scientific method. )

Daniel Dennett died last week.  He was a shining light of rationality and clarity in a world that is often a dark and murky place.  He was also the author of, among many other works, Consciousness Explained, which I think is one of the most important books ever written because it gives a plausible answer to what seems like an intractable question: what is consciousness?  And the answer is, to the extent that it is possible to condense a 450-page-long scholarly work down to a single sentence: consciousness is an illusion.

I don't know if Dennett would have agreed with my précis, and I don't expect you to believe it just because I've proclaimed it, or even because Dennett very ably (IMHO) defends it.  I might be wrong.  Dennett might be wrong.  You can read the book and judge for yourself, or you can wait for me to get around to it (and I plan to).  But for now I just want to talk about what illusions actually are and why they matter for someone trying to apply the scientific method.  In so doing I hope to persuade you only that the hypothesis that consciousness is an illusion might not be as absurd as it seems when you first encounter it.  I am not hoping to convince that it's true here -- that is much too big a task for one blog post -- only that the hypothesis is worthy of consideration and further study.

You are almost certainly reading this on a computer with a screen.  I probably don't have to convince you that that screen is a real thing.  But why do I not have to convince you of that?  Why can I take it for granted that you believe that your computer screen is a solid tangible object that actually exists?

The answer can't be merely that you can see it.  In fact, if you are reading this, you probably actually can't see most of your computer screen!  What you are seeing instead is an image on your computer screen, and that image is not a real thing.  Here, for example, is something that looks like a leopard:

but it is not a leopard, it is a picture of a leopard, and a picture of a leopard is not a leopard.  The latter is dangerous, the former not so much.  But the point is that, when a computer screen is in use, most of it does not look like a computer screen, it looks like something else.  The whole point of a computer screen is to look like other things.  Computer screens are the ultimate chameleons.

As I write this, it is still pretty easy to distinguish between real and image-inary leopards (and even imaginary leopards), but that may not be the case much longer.  Virtual reality headsets are becoming quite good.  I recently had an opportunity to try an Apple Vision Pro and it was a transformative experience.  While I was using it, I genuinely thought I was looking through a transparent pane of glass out onto the real world.  It was not until later that I realized that this was impossible, and what I was seeing was an image projected into two very small screens.  God only knows where this technology will be in another few decades.

Now take a look at this image, which is called "Rotating Snakes":

 

If you are like most people, you will see the circles moving.  (If you don't see it, try looking at the full-size image.)  Since you are almost certainly viewing this on a computer screen, a plausible explanation is that the image actually is moving, i.e. that it is not a static image like the leopard photo but a video or an animated gif, like this

 

But that turns out not to be the case.  The Rotating Snakes image is static.  There are a couple of ways to convince yourself of this.  One is to focus on very small parts of the image rather than the whole thing at once, maybe even use a sheet of paper with a hole cut in it to block out most of the image.  Another is to print the image on a sheet of paper and look at it there.

The motion you see (again, if you are typical) in Rotating Snakes is an example of an illusion.  An illusion is a perception that does not correspond to actual reality.  Somehow this image tricks your brain into seeing motion where there is none.  The feeling of looking out at the world through a pane of transparent glass in a Vision Pro is also an illusion.  And in fact the motion you see in the animated gif above is also an illusion.  That image is changing, but it's not actually moving.  And even if we put that technicality aside, you probably see a rotating circle, but the white dots that make up that circle are actually all moving in straight lines.

The Rotating Snakes image is far from unique.  Designing illusions is an entire field of endeavor in its own right.  Illusions exist for all sensory modalities.  There are auditory illusions, tactile illusions, even olfactory illusions.  The first impression of your senses is not a reliable guide to what is really out there.

There are two other kinds of perceptions besides illusions that don't correspond to reality: dreams and delusions.  You are surely already familiar with dreams.  They are a universal human experience, and they happen only while you are asleep.  But one of the characteristics of dreams is that you are generally unaware that you are asleep while you are dreaming.  Dreams can feel real at the time.  It is possibly to become aware that you are dreaming while you are dreaming.  These are called "lucid dreams".  They are rare, but not unheard of, and some people claim that you can improve your odds of experiencing one with practice.  I've had a few of them in my life, and they can be a lot of fun.  For a little while I feel like I am living in a world where real magic exists, and I can do things like fly simply by thinking about it.

But then, of course, I always wake up.

This is the thing that distinguishes dreams from illusions and delusions: dreams only happen when you are asleep.  Illusions and delusions happen when you are awake.  The difference between illusions and delusions is that delusions, like dreams, are private.  They are only experienced by one person at a time, and they are not dependent on any external sensory stimulus.

The word "delusion" is sometimes understood to be pejorative, but it need not be.  Delusions are a common part of the human experience.  Tinnitus and psychosomatic pain are delusions but the people who suffer from them are not mentally ill or "deluded".  Even schizophrenics are not necessarily "deluded" -- many schizophrenics know that (for example) the voices they hear are not real, just as people with tinnitus (I am one of them) know that the high-pitched squeal they experience is not real.  What drives them (us?) crazy is that they (we?) can't turn these sounds off.

Delusions don't even have to be unpleasant.  They can be induced by psychoactive chemicals like LSD, and (I am told -- I have not tried LSD) those experiences can be quite pleasant, sometimes even euphoric.

Illusions, on the other hand, are only experienced in response to real sensory stimulus, and for the most part in predictable ways that are the same across nearly all humans and even some animal species.  Illusions can be shared experiences.  Two people looking at the Rotating Snake illusion will experience the same illusory motion.

So how do we know that illusions are not actually faithful reflections of an underlying reality?  After all, the main reason to believe in reality at all is that it's a shared experience.  Everyone agrees that they can see cars and trees and other people, and the best explanation for that is that there really are cars and trees and people in point of actual physical (maybe even metaphysical) fact.  So why do we not draw the same conclusion when everyone sees movement when looking at Rotating Snakes?

I have already pointed out that you can print the Moving Snakes image on a sheet of paper and it will still appear to move when you look at it.  That is powerful evidence that the motion is an illusion, but it's not proof.  How can we be sure that there aren't certain patterns that, when printed on paper, actually move by some unknown mechanism?  Maybe the Moving Snakes image actually causes ink to move around on a sheet of paper somehow.  It's not a completely outrageous suggestion.  After all, we know that printing very specific patterns on a silicon chip can make it behave in very complicated ways.  How can you be sure that paper doesn't have the same ability?

The full argument that Moving Snakes is an illusion is actually quite complicated when you expand it out in full detail.  You have to get deep into the weeds of why silicon can be made to do things that ink and wood pulp can't.  But the bottom line is that we have a pretty good idea of how silicon works, and we have a pretty good idea of how paper and ink work, and if it turns out that paper can ink could be made to do anything even remotely like what silicon can do it would be Big News, and since there hasn't been any Big News about this, the best explanation of the perceived motion is that it's an illusion.

Things are very different when it comes to consciousness.  Consciousness is also a universal human perception, just like the motion in Moving Snakes, but the suggestion that it might be an illusion and not an actual reflection of reality is obviously far less of a slam-dunk than the idea that Moving Snakes is an illusion.  In fact, most people when first presented with the idea dismiss it as absurd and unworthy of further consideration.  For starters, we have a good understanding of silicon and paper, but we don't have a good understanding (yet) of human brains (Dennett's book notwithstanding).  We are nowhere near being able to definitively being able to rule out definitively the possibility that our perception of consciousness is a faithful reflection of some underlying reality that we just don't understand yet.

Another argument against consciousness being an illusion is that it is private.  All humans, and possibly some animals, experience it, but each of us only has direct experience of our own consciousness.  We cannot directly experience anyone else's.

There is also an argument from first principles that consciousness cannot be an illusion in the same way that Rotating Snakes is: optical illusions are false perceptions, but they are still perceptions.  In order to have a perception at all, whether that perception is a faithful reflection of an underlying reality or not, there has to be something real out there to do the perceiving.  Consciousness in some sense is that "thing that does the perceiving", or at least it is a perception of the thing-that-does-the-perceiving (whatever that might be) but in any case the idea that consciousness is an illusion is self-defeating: if our perception of consciousness were not a faithful reflection of some underlying reality, we could not perceive it because there would not be any real thing capable of perceiving (the illusion of) consciousness.  To quote Joe Provenzano: if consciousness is an illusion, who (or what) is being illused?

I will eventually get around to answering these questions, which will consist mainly of my summarizing Dennett's book so if you want a sneak preview you can just go read it.  Fair warning though: it is a scholarly work, and not particularly easy to follow, so you might just want to wait.  But if you're feeling ambitious, or merely curious, by all means go tot he source.

In the meantime, rest in peace, Daniel Dennett.  Your words had a profound impact on me.  I hope that mine may some day do the same for a younger generation.