In the centuries since Galileo proved heliocentrism, science has gradually come to understand more and more of our universe’s natural phenomena: gravity, quantum mechanics, even ripples in space-time. But the final frontier of science isn’t out there, says cosmologist and MIT professor Max Tegmark, it’s the world inside our heads: consciousness. It’s a highly divisive issue—some scientists think it’s unimportant or a question for philosophers, while others like Tegmark think that the human experience and the meaning and purpose of life would disappear if the lights of our consciousness were to go out. Ultimately, Tegmark thinks we can understand consciousness scientifically by finding the pattern of matter from which consciousness springs. What is the difference between your brain and the food you feed it? It’s all quarks, says Tegmark, the difference is the pattern they’re arranged into. So how can we develop a theory of consciousness? Can we build a consciousness detector? And can we really understand what we are without unlocking humanity’s greatest mystery? Tegmark muses on all of this above. Max’s latest book is Life 3.0: Being Human in the Age of Artificial Intelligence

Max Tegmark: Of all the words I know there’s no word that makes many of my colleagues more emotional and prone to foam at the mouth than the one I’m just about to say: consciousness. A lot of scientists dismiss this as complete BS and as totally irrelevant and a lot of others think this is the central thing—you have to worry about machines getting conscious and so on. What do I think? I think consciousness is both irrelevant and incredibly important. Let me explain why.

First of all, if you are chased by a heat-seeking missile it’s completely irrelevant to you whether this heat-seeking missile is conscious, whether it’s having a subjective experience, whether it feels like anything to be that heat-seeking missile, because all you care about is what the heat-seeking missile does, not how it feels. That shows that it’s a complete red herring to think that you’re safe from future AI if it’s not conscious. It’s its behavior you want to make sure is aligned with your goals.

On the other hand there is a way in which consciousness is incredibly important, I feel, and there’s also a way in which it’s absolutely fascinating. If we rewind 400 years or so, Galileo, he could’ve told you that if you throw an apple and a hazelnut they’re going to move exactly in this shape of a parabola and he can give you all the math for it, but he would have no clue why the apple was red and the hazelnut was brown or why the apple was soft and the hazelnut was hard. That seemed to him beyond science, and science back 400 years ago could only really say sensible things about this very limited domain of phenomenon to do with motion. Then came Maxwell's equations which told us all about light and colors and that became within the realm of science. Then we got to quantum mechanics, which told us why the apple is softer than the hazelnut and all the other properties of matter, and science has gradually conquered more and more of the natural phenomenon. And if you ask now what science can do it’s actually a lot faster to describe what little it is that science cannot talk about sensibly. And I think the final frontier actually is consciousness. People mean a lot of different things by that word, I simply mean subjective experience, the experience of colors, sounds, emotions and so on, that it feels like something to be me, which is quite separate from my behavior, which I could have even if I were a zombie and didn’t experience anything at all, potentially.

So why should you care about that? I care about it first of all because fundamentally that’s the basic thing we know about the world: my experiences, and I would love to understand scientifically why that is and not just leave it to philosophers. And second, it’s incredibly important also in terms of purpose and meaning. In the laws of physics there is nothing about meaning, there’s no equation for it and I feel that we shouldn’t look for our universe to give meaning to us because it’s us who give meaning to our universe because we are conscious and experiencing things. Our universe didn’t used to be conscious, it used to be just a bunch of stuff moving around and gradually these incredibly complicated patterns got arranged into our brains and we woke up and now our universe is aware of itself. We have galaxies out there that are incredibly beautiful. Why are they beautiful? Because we are consciously aware of them. We see them in our telescopes. If in the future we screw up with technology and all life goes extinct, then our universe will go back to being meaningless and just a giant waste of space, as far as I’m concerned. And when a colleague tells me they think consciousness is BS, I challenge them to tell me what is wrong with rape and torture, and I ask them to explain that to me without using the word consciousness or the word experience. Because if they can’t talk about that, it’s just the whole thing they are saying is so bad is just a bunch of electrons and quarks moving around in some particular way rather than some other particular way, and what’s so bad about that?

I feel the only way we can actually have any logical, scientific foundation of ethics, morality, purpose and meaning is precisely in terms of experience, in terms of consciousness. And this makes it really important, as we prepare for our future, to understand what this is. And I for one think that this is actually something that we can also ultimately understand scientifically. I don’t think that the difference between a living bug and a dead bug is that the living bug has some sort of secret life source in it; I think of the bugs as mechanisms and the dead bug is just a broken mechanism. Similarly I think what makes my brain conscious, but the food I ate, which got rearranged into my brain, wasn’t conscious, isn’t because they’re made of different kind of stuff; it’s the same quarks, rearranged, right? It’s the pattern into which they’re arranged. And I think it’s a scientific question: what properties does this pattern of information processing have to have for there to be a subjective experience there? You could imagine building a brain scanner—actually we have a pretty good ones at MIT where I work—and having some software in it which tests out whatever theory you have for consciousness and makes predictions for what you experience. And if I’m sitting in this machine and the computer screen tells me, okay right now I see information processing in your brain indicating that you are consciously aware of the thought of an apple. I’m like, yeah that’s right, correct. And then it says, I see information about your heartbeat in your brain and you’re aware of this. And I’m like, no I was not conscious of that. Now I’ve ruled out the theory that was implemented in the software, so it’s falsifiable, that means it was a scientific theory.

If we can one day find a theory like this, and there are some candidates on the market like Giulio Tononi’s Integrated Information Theory, for example, if we ever find any theory that keeps passing tests like that and we start taking it seriously and we can use it to build a consciousness detector, that's first of all going to be really useful. Physicians in the emergency room would love it if they get an unresponsive patient coming in, put them in the consciousness scanner and figure out whether they have locked-in syndrome and just can’t communicate but they're conscious, or whether there’s nobody home. And this will also let us understand whether future AI systems we build are conscious and whether we should feel guilty or not about switching them off. Some people might prefer that their future home-helper robot is an unconscious zombie so they don't have to feel guilty about giving it boring chores or powering it down. Some people might prefer that it’s conscious so that it can be a positive experience in there and so that they don’t feel creeped out by this machine just faking it and pretending to be conscious even though it’s a zombie. And most importantly, in the longer-term future, if far from now we have life that spreads out from Earth to other galaxies and the whole cosmos is alive and doing amazing things, if this life becomes the descendants of humanity, wouldn’t it suck if it turns out that this is all just zombies with no consciousness and the whole thing that we felt so good about before we passed away was just a play for empty benches? I feel that we should really, really tackle this final frontier of scientific ignorance, the problem of consciousness, and get this stuff figured out so we can shape a future which is truly awesome—not just from the outside that cool stuff seems to be happening, but that there’s actually someone home to experience all this.