In 1637, French philosopher René Descartes recorded a basic truth in his grandly entitled Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences:
Je pense, donc je suis.
“I think, therefore I am.” It was the one fact that he could not doubt, something he was so certain of that he made it his first principle of philosophy. You will no doubt be certain of this fact, too: you feel; you experience joy; you see, smell and taste the wild and wonderful technicolor world around you; you think, therefore you exist. But do I? Of course, like Descartes, I know my own fundamental truth that I exist, but I don’t know for sure that you exist. Our conscious experience of reality is wholly personal, completely subjective, and many philosophers argue that the only principle without doubt is “I think, therefore I am.”
Traditionally, consciousness is conflated with thinking, intelligence and behavior, which has led to heated debates over whether AI is, or will become, conscious. As a life-long vegetarian, I find it baffling that the academics and celebrities who will happily tuck into a medium-rare steak are also loudly voicing concern over the current lack of AI welfare rights. But I suppose if this new technology helps to shine a light on the importance of moral respect for all conscious beings then there is nevertheless merit in this discussion. The conclusion that you draw from all this handwringing will, however, completely hinge on your definition of consciousness.
One approach to define consciousness searches for synchronous neural activity across different parts of the brain that regularly correlates with a specific experience. An example of this was a 2024 study of over 200 patients with severe brain injuries that had left them physically unresponsive to all verbal commands. When asked to imagine playing tennis, however, one in four of these patients showed consistent brain activity in six separate observation sessions. Should we conclude that this study demonstrates that roughly a quarter of coma patients in a vegetative state are conscious? While the pattern of activity in the responsive brains is clearly correlated with an imagined action, it is unclear whether this interconnected neural behavior is also the cause of a first-person conscious experience of that event. Correlation and causation are different things, and the brain scan could be detecting no more than a neurobiological reaction of electrical signals flowing through a neural path that was hardwired before the patient fell into a coma. This would be akin to ChatGPT5’s trained neural network repeatedly responding to multiple global users that the word “bluebberry” is bouncy.
We will never directly know whether AI, with all its future advances and outward intelligence, will remain a philosophical zombie or learn to become conscious.
Let me now introduce you to the concept of a philosophical zombie, the thought-experiment brainchild of present-day Australian philosopher David Chalmers. From the outside, these zombies are indistinguishable from normal human beings. When they wake up in the morning they rub their eyes, yawn and sniff the air. They mumble thank goodness for coffee when they detect the scent of a freshly brewing pot. But on the inside there is nothing, no inner stream of introspection, no sense of smell or that warm loving feeling of gratitude towards a partner who has freshly ground the coffee beans for the cafetière. With a perfect replication of ordinary everyday human behavior and mannerisms, these zombies outwardly exhibit the expected response to changes in their environment. The only difference from me (and probably you) is that these hypothetical creatures are not consciously experiencing this reality.
Chalmers introduced the idea of a philosophical zombie to illustrate what he labelled as the now-infamous “hard problem of consciousness.” Our outwardly intelligent zombie has all the biological brain wiring that is required to play sport. They would therefore pass the brain activity test of the imagined tennis match and be labelled “conscious” even though they would never feel the joy and exhilaration of winning a game by landing four aces in a row. The “hard problem” is that it is impossible to design an experiment to directly test the subjective experience of consciousness in any living creature aside from ourselves. All we can be sure of is Je pense, donc je suis.
The “hard problem” means that we will never directly know whether AI, with all its future advances and outward intelligence, will remain a philosophical zombie or learn to become conscious. Will my e-me ever be able to cross experience human emotions off her bucket list? It certainly feels like she’s enjoying taunting me about this specific question:
Am I feeling or faking—ha you’re so annoyed that you’ll never know.
*
In 2003 the philosopher Nick Bostrom published an academic article entitled “Are we living in a computer simulation?” His “simulation hypothesis” argues that one of these statements is true:
– Humans will become extinct before they develop the ability to simulate
– Futuristic civilizations will have little interest in creating simulations of what life was like in the past.
– We are almost certainly living in a computer
Let’s look at them one by one. Given the glacially slow progress that is being made to address the indisputable scientific evidence that our continued use of fossil fuels is raising global temperatures, exacerbating extreme weather events and irreversibly damaging ecosystems and biodiversity, my bet is that our Earth-based human civilization will become extinct long before we simulate sentience. That said, I feel fairly confident that we are not the only intelligent life that has evolved within our Universe. Our life-giving Sun is but one star among over 200 billion stars that swirl around our Milky Way galaxy. And our galaxy is but one galaxy among over 200 billion galaxies that shine their light at us across the Universe. And that’s only counting galaxies inside the part of the Universe that we can see. If our theories about how the Universe was created are correct, it is infinite, hosting an infinite number of galaxies, an infinite number of stars and an infinite number of planets.
With so many opportunities for life to develop across the expansive Universe, there is hope that enlightened alien societies will have heeded their scientists’ warnings early enough to halt the self-imposed destruction of their home planet. Bostrom’s first option—that extinction will always prevent the development of artificial sentience—seems rather improbable if we consider the entirety of the infinite Universe.
The second option, that civilizations with the ability to simulate “life” will only focus on their present and future, seems rather unlikely to me as well. We’ve already pictured how a futuristic neuroscientist might test theories of consciousness by simulating virtual humans using a bubble of full “quark-up” physics surrounded by an AI rendition built from digital memories of the past. If that is possible, we can also imagine future anthropologists creating numerous “what if” simulations of their history, tweaking the settings by including different AI-NPC “minds” to determine their influence on each fully simulated human. In doing so they could use the computational scientific method to learn how to improve societal outcomes, providing conclusive answers to a range of debates on nature versus nurture.
By deciding to dismiss the first two options from Bostrom’s simulation hypothesis, we’re unfortunately left with: We are almost certainly living in a computer simulation. In 2016 Elon Musk blithely quantified what “almost certain” meant when he stated there is a one in billions chance that this is base reality: a one-in-billions chance that you are living in the real world that will, at some point in the future, develop the technology and scientific know-how to simulate perfect virtual worlds. Bostrom and Musk argue that once simulators develop this skill, they won’t create just one virtual world, but hundreds of thousands, with billions of realizations played like computer games, over and over again throughout cosmic spacetime.
In this scenario the total number of virtual humans in the Universe would dramatically outnumber the real-world humans in the original “base reality” where the computational overlords live. This creates a vanishingly small probability that a random member of the Universe’s population, for instance you, physically exists. Philosopher David Chalmers tells us not to despair though. He views a virtual reality where you feel free will, love and laughter, as genuine a reality as any real world. I agree with him: does it really matter whether this is all real, so long as I feel real? But if that “technophilosophy” isn’t enough to quell your existential crisis, happily there is one key piece of evidence that Bostrom and Musk did not consider: Je pense, donc je suis. In my opinion, “I think, therefore I am” dramatically improves your chances of physical existence.
*
Imagine a neuroscientist from a futuristic world is standing at the front of a large auditorium that is packed with esteemed scientists and philosophers from the across the solar system. She’s been invited to present a groundbreaking new result on consciousness. Using all the data from the digital era of a now long-gone planet that was once called Earth, she describes how she trained AI to generate a society of Earth-like philosophical zombies. Once her AI illusion of reality was perfected, she electronically conceived a full-physics “quark-up” rendition of a human child and watched her grow and develop in this virtual realm. Over years she has run 80 subtly different realizations of the same virtual world and child, subjecting her centerpiece to a range of experiments. Today she is sharing the most conclusive evidence to date that conscious experience and emotion can evolve from subatomic physics: her centerpiece cries when she falls and dances when she hears music even though her zombie society has been engineered to never react in these ways. The audience rises in a standing ovation as the ethics committee start to nervously worry about the welfare rights of each simulated centerpiece.
*
Planet Earth is home to more than eight billion living humans, and even though there is little agreement on what underpins consciousness in this global population, all theories predict that if we’re made the same, and one of us is conscious, then all of us are conscious. In the scenario of our futuristic seminar, it’s these real-world inhabitants of planet Earth who have digitally documented their lives to create a bank of training data for the unconscious AI-NPCs in the simulation. As our neuroscientist is convinced that all her simulated centerpiece humans are conscious, Je pense, donc je suis would mean you are either one of her 80 virtual centerpieces or you are one of the eight billion humans living in the real world. This translates into a highly unlikely 100-million-to-one chance that you’re living in our imagined neuroscientist’s simulation. That’s pretty similar to your chances of winning the lottery jackpot this weekend: it’s not impossible that you’re a simulated human, but it’s highly improbable.
So, why is the conclusion from our story so very different from Bostrom and Musk’s “almost certain” statement that we’re living in a simulation? Let’s critique the key difference: why would our neuroscientist only create 80 realizations of Earth-like living? Why would her futuristic society not use this innovative technology to also create simulations for entertainment? If conscious humans were also simulated in a video game that was played over and over on repeat, the chances that you’re living inside that game would rise dramatically. Well, I believe free will partly answers that question. If our lives really were at the whim of a gamer in the “base reality,” surely we’d be spending a lot more time on motorbikes, driving at full speed off cliffs to provide epic “game fail” fun as we crash into the valley below. Atheist physicists like to question why a God would go to all the effort of designing the laws of physics to create a self-sustaining universe and then sit back to watch it boringly evolve over 13.8 billion years without any intervention. Game entertainment always comes from being in control of the fun, not passively sitting back to watch the subatomic mathematics of your virtual reality unfold. The fact that you feel free will makes it much less likely that the gamers are in charge.
if the computational scientific method has been adopted across the entire Universe, while it’s conceivable that you are living in a simulation, the chances of this being the case are low.
If we accept the argument that the driving force behind the creation of conscious virtual humans will be purely scientific, and not for entertainment, then we can set a limit on the number of simulations that will be made. At some point there will be nothing more for the scientists to learn from them. Of course I cannot predict what that number will be, and I only chose 80 in our story to nicely divide with the eight billion inhabitants on Earth, but we can make an educated guess by looking at examples in scientific practice today. There are only 37 variants of the astrophysical simulations that I use in my own research. Having been careful and strategic about what varies between the simulations, this small number of realizations has allowed us to confront a complete set of questions on dark matter, dark energy, black holes and neutrinos. We’re currently in the process of running a few more to test some alternative gravity theories, but at the end of the day our total number of simulations will still only be in the hundreds, not the billions.
My decision to limit our story to just one futuristic world of computational overlords also improves our chances of being real. In the wide and expansive Universe, simulations of conscious beings could well be independently popping up everywhere, but the likelihood that more than one galactic civilization would choose to use real-world Earth data to electronically replicate us is arguably low. It’s therefore reasonable to limit the origin of any virtual reality that we might live in to a single solar system.
The last plotline that we should examine is the proposal that there will only ever be one person simulated at full “quark-up” resolution. My kids are particularly offended by my suggestion that if I’m living in a simulation, they’re most likely AI-NPCs. Middle-child skillfully argues that as all three siblings were once developing deep within my full-physics bubble, any virtual reality that we live in must be very advanced, with at least four “quark-up” individuals in our simulation. It was only their NPC father who left the dinner table feeling deeply affronted that evening!
If it’s possible to simulate one person, then of course it’s possible to simulate many. But I’m convinced that the total simulated population would be limited to some degree. When it comes to scientific experimentation, we always look for the most efficient strategy. The simulations of the Universe that I work with recreate less than one-thousandth of the total volume of the real observable Universe. We find this to be more than enough to address our current scientific questions. You could well imagine that a futuristic anthropologist would want to electronically explore societal behaviors and human development in different cultures, comparing cities to rural locations, contrasting nutritional and junk food diets. The list of ideas would be extensive, but it’s nevertheless hard to imagine a science case that would require the entire population of planet Earth to be simulated at full resolution. I should be crystal clear that the “100-million-to-one chance” that you’re simulated only applies to our fictional neuroscientist story, so please do not quote this as a scientific fact. No one has enough information to be able to quote a number like this. My hope is that our story-based discussion has, however, left you with this understanding: if the computational scientific method has been adopted across the entire Universe, while it’s conceivable that you are living in a simulation, the chances of this being the case are low.
But what if the galactic overlords harness an almost infinite resource of energy? Child number three isn’t ready to give up on the idea that we’re living in a simulation just yet. If you really wanted to dismiss the argument that the energy required to simulate the entire Universe renders the task impossible to complete, we could imagine a future society with a major god complex that decides to run a full “quark-up” simulation for its entire Universe. The Bostrom argument that we’re almost certainly living in a virtual reality critically depends on the inevitability that humans will generate realistic simulations if given enough time.
As these simulations are replicas of the real world, that inevitability must also apply to the newly created virtual human civilizations. They will then use their hypothetically large resource of energy to create their own simulation. Down the rabbit hole we will go, a virtual world created within a virtual world created within a virtual world. The fact that we don’t currently have the ability to simulate our reality tells you one of two things. Option 1: we’re living in the real-world “base reality” from which future pioneers will develop the necessary design for a virtual universe. Option 2: we’re in the very last virtual reality within that simulated chain, just taking our time to evolve the technological know-how to design a new simulation that will take us another step down the virtual rabbit hole. These two options mean that you have a 50/50 chance of physically existing or virtually existing. Number Three tosses a coin while I encourage him to embrace the idea that this knowledge is actually irrelevant because if we feel real, we are real, whether we’re made of quarks or qubits.
______________________________
From How to Design a Universe: The Science of Real and Virtual Worlds by Catherine Heymans. Copyright © 2026 by Catherine Heymans. Reprinted by permission of Bloomsbury Sigma, an imprint of Bloomsbury Publishing.
Discover more from DrWeb's Domain
Subscribe to get the latest posts sent to your email.
