The gist of the debate is that Lee sees computation as an invention of the universe, for example by way of biological life that created brains and minds which created digital computing machines. Joscha proposes that the universe may, itself, be a computer, for example in the way that John Conway’s Game of Life cellular automaton turns out to be a Turing Complete computer and on top of which can be built other computing machines including the Game of Life itself. This is part of a larger question: Is reality a simulation or the result of some type of vast computing machine?
Let’s tackle this question in parts.
Systems in our universe are composed of layered substrates
Life as we know it is composed of layered substrates in which a “new world” forms on top of each substrate layer that underlies it. The world of atoms is the basis of molecules and chemistry. Molecules are the basis of the dynamic machine that is the biological cell. Colonies of cells form the substrate of the human body including the dynamic behaving brain. The neural activity networks of the brain then act as a substrate to support the mind, cognition, and consciousness.
At each layer, there is a mystery, which is what came before that layer’s creation? Biological cells split off to form new cells, but the birth of the first cell is mysterious, and the cell’s dissolution renders its prior life history irrelevant. Consciousness is the same way. We emerge from babies into becoming self-aware, but there is a paradoxical mystery from our point of view: why are we here and not somewhere else? Where did we come from? What happens when we die? Each system makes sense within its own universe, but its meaning before its own beginning or after its own end is ambiguous and paradoxical within its own frame of reference.
What happens if we take the substrate view and explore in the other, outward, direction? Below our consciousness is the brain, and then biological cells, and ultimately the chemistry and quantum particles that form the standard model of physics. But what is below that? Astrophysics can play time backwards to imagine the beginning of our universe at Big Bang, but what came before the beginning?
The famous book Flatland, written in 1884, explored a similar reality-frame layering paradox. The book proposes a 2D world called “Flatland” and imagines 3D objects passing through this 2D universe and asks: What would it be like if a 4D object were to pass through our 3D reality?
The challenge with existence on a substrate. The world outside (or below) the higher-order world is paradoxical and possibly unknowable within the reality frame of world on the substrate.
A computer may not be the best model for an underlying reality substrate
This brings us to our known universe. Is there a substrate underneath? And if so, is it continuous or discrete? And if discrete, could it be a computer, where a computer is an abstract discrete stepping transactional system? And if so, does that mean we are living inside a simulation?
It seems unlikely that the universe is contained inside a “computer,” primarily because the universe does not appear to be very computable in the traditional sense. The Schrödinger equations are unsolvable outside of simple cases like the hydrogen atom. And while the Schrödinger equations suggest a deterministic universe, that is only on paper. In practice, the state of even a tiny piece of the universe such is inaccessible to us due to Heisenberg’s uncertainty principle and the impossibility of non-disruptive measurement.
While there might be a larger frame of which we are a part, viewing this frame as computation runs into three problems:
- There does not seem to be any evidence to justify restricting this larger frame to the transactional state abstraction of a computer
- A computer does not seem like the most natural fit given the spatially continuous nature of matter and particles; the universe does not appear composed of spatial “cells” or other possible units of computable simulation.
- Simulations generally suffer from a problem of resolution in which an abstract model is approximated with associated rounding errors. In the virtual world of a video game, there are flaws in the simulation. These are kept hidden because the simulation will increase the resolution as we zoom in, but this is because the game is optimizing for individual single conscious observers with perceptual limitations. The game couldn’t run in “full resolution” everywhere because the resolution, no matter how fine, is still a finite estimation.
We have limited access to information about any underlying substrate
If a larger reality frame is out there — a substrate below the currently known reality of the universe — it may be unknowable to us because we are “trapped” on the inside, with limited or possibly zero ability to interact with the substrate below that would allow us to collect evidence one way or the other.
The reason we are able to see outside the reality frame of our own consciousness is because the underlying machinery reveals itself to us in the form of sensory illusions and the discoveries of science. Experimental anomalies give us clues into how the underlying substrate works, and from there we are able to form predictive theories that give us confidence that we have correctly understood the underlying substrate, at least to a reasonable approximation. This process of evidence-led examination reveals to us that what is actually going on is different from how it appears. For example we now know that there is no actual color “red” in the universe and that this is rather how certain electromagnetic radiation wavelengths appear to our perceptual machinery in certain contexts.
Advanced scientific instruments, such as microscopes and particle accelerators, have allowed us to see beyond the illusions in which we live and peer into the mechanics of the substrate below. We occasionally find cracks in our presumed natural world that reveal how the underlying world works, such as the discovery looking downward of cells, molecules, the atom, or the particles of quantum physics. But we have not yet found measurements that “don’t add up” at the level of physics which would hint at a larger “computational” frame preceding the Big Bang.
Occam’s razor suggest the underlying substrate is not a Turing machine
If the history of science is any guide, then a larger reality frame is likely out there to be found. While the quantized nature of particles may invite a model of a computational nature, it is not clear that this adds anything to the standard model, and it may even subtract. The standard model of physics seems to do a better job of describing how the universe works than a more restricted “Turing Machine” type model. If there is a larger model to the universe, it seems likely to be even more alien than quantum physics rather than something as fully understood as the transactional abstraction of Turning Machines.
Until there is some evidence to support the idea that a larger reality is best understood as a computer, Occam’s Razor requires to reject the Turing Machine assumption.
We may be living in a simulation after all — a neural simulation
It may be that we are living in a machine-simulation after all.
A widely discussed view in neuroscience is that the consciousness is a dynamic construction of the brain made possible by neural activity. In a sense, the brain is operating a virtual machine that generates the theater of consciousness along with beliefs about the world that include ourselves at the center of it. When we emerge from dreamless sleep, the brain stem fires up our conscious world, with alpha and beta waves at 10 to 24 Hz providing the synchronizing rhythm that drives the organization of thought and experience. The perceptual experiences in this world are informed by input from our senses, but what we experience are not our senses directly but what amounts to a simplified hallucination that enables us to interact effectively with our environment.
In this sense, we are living in a simulation. What we don’t know is whether the world that we perceive inside our neural simulation is, itself, also a simulation, and if so, what type of machine it might be running on. While a Turing Machine does not seem to be the most likely candidate due to being too limited and sequentially transactional, the universe might be a different sort of machine.
- Is the human brain analog or digital? — Is the substrate of the brain and our consciousness analog, digital, or something else?
- Are we Living in a Computer Simulation? (2016, Scientific American) — Reports on a debate between Neil DeGrasse Tyson, David Chalmers, Max Tegmark, and others as part of the annual Isaac Asimov Memorial Debate.