Determinism from the Perspective of the Simulation Argument

It’s been almost two years since I last wrote about Free Will vs Determinism. The argument is the standard one, that since everything in the universe is governed by physical laws, it is completely deterministic. However, because it is not possible to to simulate the entire universe, it is at the same time unpredictable, so we should act as if there is free will.

However, one obstacle stood in the way of that argument: Quantum randomness.

With true randomness, we cannot say that the universe is deterministic. But with the basis that everything is governed by natural laws, it makes equally no sense to assert the existence of free will. Because, if all the same random events occurred the same way, another “run” of the universe would have the exact same result.

Even when you are thinking in your head at this very moment that you have free will, what is really most likely happening is that chemical processes in your brain have led your conscience to make that decision. If the entire universe “restarted” with the exact same sequence of random events, you would make the exact same decision again.

The Simulation Argument.

This is where the argument gets interesting. There is a very scary paper written by philosopher Nick Bostrom called, “Are You Living in a Computer Simulation?” It is scary because the implication, given a couple of premises, is that we are almost certainly living in a computer simulation. Not only that, but the argument posits that our simulators are themselves extremely likely to be in a simulation, and those simulators are likely too to be in a simulation, etc.

With the near certainty that we are in a simulation, determinism can only become stronger. You have probably heard of things called random number generators. A lot of these work by taking a seed number, and then running it through a specialized function over and over again, resulting in what is known as pseudorandom. These generating sequences that seem random but are completely deterministic, if you know where it started, i.e., the seed number and the algorithm.

This means that, providing our simulation ancestors, the beings who simulated our universe, are using similar ideas of random number generation, all the “random” quantum events we measure in our universe could actually be a completely determined sequence, perhaps by an algorithm so complex that it would be physically impossible to calculate from within this universe.

Of course, this is provided two premises:

  1. We are in a simulation.
  2. Our simulation could use pseudorandom number generation.

Premise 1 is actually very likely, from sheer numbers in the argument. It is Step 2 that is undecidable and for us to choose. If we accept it, this would imply our entire universe, including quantum events, is completely determined. And if we reject it, it would not rule out the possibility of total determinism either.


Given some invented definitions, here are the levels for free will vs determinism in the simulation framework:

  1. Total Free Will: Consciousness is special, i.e. not bound by physical laws. Free will comes from a higher source. (Question: What if this higher source is bound by physical laws in its universe?)
  2. Weak (Random) Free Will: Consciousness is not special, i.e. it is bound by physical laws. However, there are events in the universe that exhibit true randomness, so it is not fully deterministic.
  3. Weak (Random) Determinism: True randomness exists. However, given a specific set of outcomes of random events, the universe runs the same way.
  4. Total Determinism: True randomness does not exist, only pseudorandom exists. Thus, our universe will always run the same way under the same starting conditions.

Free Will: How We Do and Do Not Have It

Today’s topic of free will was chosen by Virginia W at Westwood High School. But was the topic freely chosen or was it already determined?

The answer has to do with the way our universe works. According to modern scientific theory, the universe can be broken down into a number of rules which govern how things interact. These rules are often presented to us as a series of confounding mathematical equations.

That, for example, is a formula of general relativity. Which would explain things including black holes:

[Both images courtesy of Wikipedia. For the rest of the images in this searches, thank Google search.]

Now, if you would agree at least that the movement of galaxies and stars are determined by rules, the laws of physics, the question is how far down does this go? Rather, a more interesting way is to look the opposite way, starting from the tiniest things we know: subatomic particles:

We can’t actually see them. But we know they are there. And we know about their properties through the laws of physics nonetheless.

How far up does this go? Combine subatomic particles together in certain ways and you get atoms. Put atoms together and you’ve got molecules, but wait, aren’t we now in the realm of chemistry?

These things are governed by formulas nonetheless. And when we put a bunch of these molecules together, we get a cell. Have the right kind of cell, and it’s a neuron. Your brain is a vast collection of interacting neurons:

Wouldn’t it follow that these also obey some rules? Even though we haven’t found these rules yet, all the neuron’s building blocks follow physical laws that are never violated. I remember Stumbling Upon this picture a couple of years ago, and it is still shocking. It shows the uncanny similarity between the structure of neuron clusters and the structure of galaxy clusters:

Point is, everything, including your brain, is governed by a set of rules. (You might hear in the news every so often that some law is broken, but that is only because the theory about the rule was incorrect, not the rule itself.)

Here is the tricky part. Suppose we knew all the rules, knew what the universe started from, and had a sufficiently powerful enough computer to run our universe as a simulation. (All 3 of these are far beyond are reach at the moment, especially the third, which is impossible, but is here for sake of thought experiment.) Because of the rules, the simulation would start running and emulating our universe exactly.

Sometime in the simulation a star would form, and there would be eight planets around it. On the third closest one, life forms would appear, eventually ones intelligent enough to question their own existence. They would ask, “Do we have free will?” And I’ll say, “No, but…

The answer is no, because if everything is governed by rules, then there is not any “intelligence” inside the simulation that is not part of something programmed into the simulation beforehand. What happens in the simulation only depends on what rules we decided upon and in what condition we started it, both choices having been made before the simulation ever began. There is no actual “free will” inside the simulation.

But there is always a “but.” Even supposing we figured out all the laws of our universe and its initial state, it would be physically impossible to create a simulation that could run our universe in at least real time.

Suppose in some simulation you have some number of particles. Further supposing that your computer has perfect, 100% efficiency, in that one particle in the computer could match one particle in the simulation, you would not be able to ever run the simulation, because you need as many particles in your computer as your entire universe contains! So you could run a partial simulation or a less detailed one, but this wouldn’t match your universe. Or you could slow it down, so you simulate only a fraction of the universe at a time (but still you would need storage).

The point here is, we physically cannot simulate our universe. We would need more particles than our universe contains. Even if we could tap into the resources of another universe, we would run into the problem that eventually in the simulation, the resources of another simulated universe would be tapped, thus requiring even more resources in the original universe. And so on.

So even though the universe might be determined, we can treat life as if we have free will anyways because we can never know what will come next. For all practical purposes, we do indeed possess free will. But theoretically, we don’t.

Edit: Here is a post I wrote later on an intriguing simulation aspect of determinism.