Evidence against
[edit] Falsifiability
While the simulation argument is a skeptical view of reality, and proposes an interesting question regarding nature and technology, there are several problems if it is proposed as a serious hypothesis. Firstly, the simulation argument is completely
unfalsifiable as it is impossible to devise an experiment to test the hypothesis and potentially prove it to be false. Even if a hypothetical experiment was devised and turned out negative (that the world was not simulated) it would still be insufficient because there is the potential that this is merely what the simulation wants us to think, or we are living inside a simulation inside a simulation. This, according to widely accepted definitions, places it firmly in the field of
pseudoscience. Any serious suggestion that we do live in a simulation (as opposed to discussion of the probabilities, assumptions and the potential technologies involved, which is academically sound) relies purely on
faith and
argument by assertion. This makes the simulation argument, as an explanation of reality, more like a
religion - regardless of the assertions of transhumanists that the maths works out.
[3]
[edit] Occam's razor
Occam's razor can also be used to guide us in working out whether to accept the simulation argument as a real explanation of reality. This suggests that, all other things being equal, the hypothesis with fewest assumptions is most likely correct. Given that the simulation argument rests on numerous assumptions regarding the means and motives of the simulators and the technology that powers them, Occam's razor would suggest that simulation is the far more complex hypothesis compared to non-simulation.
Although a simulated reality is unfalsifiable, an answer can be readily obtained by using Occam's razor, since any explanation of the world around us that involves evil alien overlords having wiped our memories and coercing us into participating in a gigantic
MMORPG for some unknown nefarious purpose is a good deal more complex than just trusting our own senses. The idea is also recursive, as even if you became aware of being simulated, you couldn't tell - in a sufficiently advanced simulation - if this outside world was
also simulated, and that the alien overlords or future humans were also being studied within a simulation and so on.
[edit] Feasibility
Three bodies moving chaotically under gravity, as a solution to their motion cannot be solved analytically. The question is; how does this little problem of physics affect a hypothetical simulation of the universe?
One of the most well-known problems in mathematics and physics is the "three-body problem" or the "
n-body problem", which states that it is impossible to create an closed-form analytical solution to a system with more than two parts interacting with each other. Solving for one body is trivial, solving for two is possible because you effectively "freeze" one of the bodies, thus reducing it to a one-body problem, but for three or more - except in very trivial cases where certain mathematical approximations are perfectly applicable to a real system - is not possible. Such systems display
chaotic behaviour. This, on its own, doesn't necessarily preclude simulation as determining forces in a many-body system and then advancing it by one "frame" is possible, and so only precludes the existence of a deterministic equation to solve anything. However, it does often make simulation and generation of a suitable set of equations (presumably, by any meaningful definition of "simulated reality", the simulation functions on such solvable mathematics) to describe a system.
When attempting to make mathematical models of reality, certain assumptions and approximations are made in order to describe systems. If the universe was being described by an analytical process
anyway, such things would be unlikely to be needed, and so basic two-body approximations should be perfectly analogous to experimental behaviour. However, such things are rarely seen. In the field of quantum computation (computer models of quantum systems such as atoms and molecules) introduction of such approximations to make even the simplest models disagree with reality considerably. In order to compensate for any approximations made in order to make the systems computable, computational cost must increase significantly - in computational chemistry, the cost of a simulation scales by
at least the fourth power of the number of bodies and functions being considered. To make a "perfect" simulation, an infinite number of functions needs to be considered. To accurately model the interaction of just two water molecules (perhaps the simplest chemically interesting system) requires over 500 functions to bring the result within experimental error. This sort of issue extends from
chemistry and into
physics, where the interactions modelled by Feynman diagrams can produce an indefinite number of particle interactions, each contributing to the observed properties of a particle. Many hundreds, if not thousands, of just the smallest of these possible diagrams are required to make reasonably accurate predictions of the energies of sub-atomic particles. To make an "accurate" picture of the particle system requires an infinite number - each and every possible Feynman diagram up to an infinite size. These are very small and isolated systems, an entire universe raises the complexity beyond what can be readily imagined.
Basic mechanics, therefore, makes a simulation of the universe a considerably bigger task than most proponents of a simulated reality seem to grasp. A simulation would have to be "perfect", as otherwise we would begin to observe flaws in real-world mechanics. Yet the number of interactions required to make such a "perfect" simulation are vast, and in some cases require an infinite number of functions operating on each other to describe. Perhaps the only way to solve this would be to assume "simulation" is an analogy for how the universe (operating under the laws of quantum mechanics) acts
like a quantum computer - and therefore it can "calculate" itself. But then, that doesn't really say the same thing as "we exist in someone else's simulation".
[edit] The interference question
Simulations within the bounds of our universe frequently exhibit certain qualities. All of these are bound up in the term's inherit indication of purpose.
- Purposeful recreation of some aspect of the extant universe to understand the driving principles of that component. It is hard to imagine the purpose of simulating so large a universe, when pieces have tiny impact on others. The behaviors under scrutiny would need to be beyond comprehension to justify such a large dataset.
- Interference with the simulation. While not universally true, many computerized simulations performed by humans allow for alterations to the simulation to see their effects. The observable history of the universe shows no sudden or impossible changes.
[edit] Problems with the specific assumptions
The 7 points of the argument above can conceivably be false, the following covers the reasoning as to why they may not be true.
- The ability to simulate: Conceivably computers could simulate human personalities, which is the basis for all research in artificial intelligence. The existence of a non-natural soul would destroy this assumption, but generally this is likely to be a very true point. This property only needs to apply in principle because the simulators do not necessarily have to be our future selves, so if the human race doesn't, in fact, develop artificial intelligence this can't discount the simulation hypothesis.
- How to simulate: Even if a computer of silicon chips couldn't simulate a mind, a computer made of neurons identical to a brain could - and a computer of silicon chips simulating something identical to a brain certainly could. Emergent phenomena imply that consciousness can be independent of the medium it is made out of and is instead dependent on the patterns that medium creates; without begging dualism, the difference in output between a human brain and a perfectly identical computerised copy is zero.
- Simulation of people and environment: Arguments against the assumptions begin here. By handwaving the hardware and energy requirements to achieve such a thing, you could make billions of personalities if you can simulate one successfully. However, this is making a vast assumption; would people even want to? Proponents of the simulation argument may suggest that saying "no" to this is making assumptions about a race of beings so powerful that we couldn't possibly second-guess them. But this works in both directions; how could we second-guess an unknowable race of transhuman beings to conclude that they would simulate people.
- Computational power: Given Moore's Law, and past increases in computing power, it's sort of a no brainer that much more powerful computers could exist in the future. It doesn't automatically follow they will be powerful enough and energy efficient enough to simulate the billions of sentient beings and the supporting universe required to form a simulation. See computing complexity below.
- Multiple simulations: Similar to the above, it is a non sequitur to assume that because something is possible that it will be done repeatedly. Humans do, of course, have a propensity to do things "just because", but there could be practical considerations as well as the question "why bother?". See motives below.
- More simulated entities than real entities: This is the point that the simulation argument rests on - that there are more simulated entities than real entities. Both motives and practicalities can conspire against this assumption. It can easily be impossible to simulate a universe and considered pointless to do so.
- Concluding that we are a simulation: Conceptually it's possible that we are a simulation. But given the active evidence and unfalsifiability of the proposal it's equally possible that aliens are responsible for human civilization, or possible that both aliens and humans exist in a simulation, and that simulated aliens are responsible for our simulated civilization.
[edit] Complexity
It is not possible for something to be simulated on something else that is less complex than itself. This is easily demonstrated with data storage alone. The number of atoms in a hard drive will be something along the order of 1024 or so, a vast number. To simulate this hard drive, one would have to record the positions of all the atoms. To define these positions in space requires three co-ordinates, XYZ, and these must be defined with sufficient resolution - at least 10-11 significant figures for something the size of a hard-drive. And each atom would have to have a label to distinguish it and that would have to be 24 significant figures to account for the sheer number of them. So at least 100 bits of information are required
per atom and that's just for their locations. This totals up at 10.3 yottabytes, or 10.3 x1012 terabytes - so that's 1012 hard disks just to store the information used to make 1! Simulating an entire universe goes into even more ridiculous territory. Given this, it would be an easier task to simulate a brain by building an actual brain out of neurons than it would be to describe those neurons in a computer.
An upper bound to what can be computed inside the universe - given the age of the universe, the speed of light, and the ability to manipulate and move information at the smallest possible levels - has been computed to be around 10120 bits.
[4] This has been described as the "computing power of the universe", or if it
was a computer how much it would take to work it out and what it could work out inside it. Of course, it could still be calculated - given
any amount of time - inside any Turing complete machine, the question is whether this universe is capable of simulating a similar universe inside it.
Due to the complexity, whatever is simulating
this universe must be considerably larger and more complex than this one. So the flavours of the argument that suggest that it is future humans (i.e., from our universe) simulating us is likely to be very false indeed, as we would be completely unable to simulate our entire universe - even assuming compression, efficiency and extended time - within our universe itself. The only explanation to handwave this point is to state that this universe
must be a very poor approximation of the "real" universe - akin to running dynamics calculations on a simple shape rather than a complex 3D object, or condensing large molecules into single atoms for computational chemistry calculations. There is no way to
outright disprove the general idea, of course, but some of the assumptions can still be looked at.
[edit] Motives
The underlying points made in the simulated reality argument require making a lot of assumptions about the motives of the simulators. Namely assuming that because they could, they would simulate a reality. One can question what it is possible to achieve by simulating an entire reality and then simulating
more realities to go with it. There are numerous day-to-day activities associated with the world around us that would be of little interest to researchers or potential explorers and it would seem pointless to simulate these entirely rather than just focusing on more interesting areas and diverting the resources to more productive areas. However, this would be making decisions and assumptions about whatever godlike-beings are simulating the universe - maybe to them, we're no more complex than an 8-bit computer game.
