My question is what makes something a simulation? Or more specifically, does intent matter for calling something a simulation?

Consider the following:

Case #1:a well-known xkcd http://xkcd.com/505/ where by moving around a bunch of rocks, the guy implements a simulation of the universe.

Case #2: While I certainly don't think the substrate of the computer matters, what if it was the wind doing the rock moving? If you waited long enough surely the wind would implement the simulation. Most likely of course the simulated being would be in a Boltzman-brain type simulation ending the very next instant.

If Case #2 is a simulation, then then why shouldn't we just expect ourselves to live in a simulation created by some randomly jittering particles? If it does not qualify, then that amounts to saying that somehow we need the guy's intention to run the simulation.

I think that the criterion of intention as a condition for something to be a simulation is crazy.

  • Hello sir! :) I actually still don't understand your question. Your title question is unanswerable because it's not clear what you mean by "real". The first 2 sentences in the body seem to be separate questions from each other and the title question. The 1st is asking for the definition of "simulation", something you can just look up, right? The 2nd seems to be the only one that might have philosophical merit but it's not clear what you are getting at. Can you first establish your definition of "simulation" and explain why you think it matters whether a simulation is accidental or intended? – stoicfury Sep 26 '14 at 16:52

There is a more general question which is - what constitutes an implementation of a computation.

Notable philosophers have been debating this question for several decades.

In correlation to your example of computation by wind and the question of intention, Searle argued in his Chinese room thought experiment that computation is observer relative:

Computation, or syntax, is “observer-relative”, not an intrinsic feature of reality: “…you can assign a computational interpretation to anything” (Searle 2002b, p. 17), even the molecules in the paint on the wall.


the molecules in a wall might be interpreted as implementing the Wordstar program (an early word processing program) because “there is some pattern in the molecule movements which is isomorphic with the formal structure of Wordstar” (Searle 1990b, p. 27)

To this and similar arguments Chalmers responded in Does a Rock Implement Every Finite-State Automaton? and later developed what he calls a theory of implementation in A Computational Foundation for the Study of Cognition.


I take it that a lot hinges on how we are defining simulation. Rather than quibble, I'm just going to cite Merriam Webster on this:

something that is made to look, feel, or behave like something else especially so that it can be studied or used to train people

Here, I think the key is the word "made". The same idea is expressed in their longer definition. Seems pretty clear that this is how the term is most often used and does require intention.

I take it you're working from a different concept where something is a simulation if it accurately describes the operation of something else. Moreover, you are not restricting that to any extensible period of time.

I think we should reject that definition for one quite simple reason: it makes everything a simulation and worse it makes everything a simulation that has no value or meaning. Part of the point of simulations is to provide predictive powers by expansively applying what we know. Arbitrarily coincidental arrangements don't mean anything or help with anything.

  • From our perspective outside the simulation a random coincidental arrangement would be uninteresting and unhelpful as you say. But say in the xkcd rock simulation, the man moving the rocks made his simulated agents suffer. Then we would care if random arrangements by the wind could cause similar suffering right? – CoffeeCat Sep 26 '14 at 11:13
  • I hadn't bothered looking at your link. I think you and the author of xkcd are confusing the meaning of simulator with something else. It seems like your question is "would it matter if we were in a simulator involving intention versus a reality generated by buffeting winds?" I guess my answer would be there's no reason to believe we are in either. But yes it would matter whether what happens is planned or not. But maybe you should study Descartes to get a real philosophical response. – virmaior Sep 26 '14 at 12:03

The criterion of intention is wrong, but not for the reason you think. You can try to simulate something on a computer and fail. There are knowledge criteria for a particular system to count as a simulator.

A computation is a physical process takes some input manipulates the information in the input in a specified way and produces an output. For example, a controlled not gate takes two bits and performs the not gate on the second bit if the first is zero. I will use this to illustrate the knowledge requirements for some system to count as a simulator.

If an alleged simulator of a controlled not gate doesn't produce the right mapping in all cases, then it is not a controlled not gate. More generally, if the simulator does not perform the relevant mapping for all of the possible inputs then it doesn't compute the specified function. The computer has to instantiate knowledge about how to do the controlled not gate.

In addition there has to be an interpretation of the inputs and outputs known in advance under which the simulator is performing the relevant manipulation. This is required to guard against doing the following. Suppose that I have two coins and I place them both heads up on the table in front of me. I could take two bits with the value 1 0 say and say that when the coins are both heads at this particular time t1 the heads on the one on the left stands for 1 and the heads on the other stands for 0. I could then wait for two minutes, work out that the controlled not of 1 0 is 1 1 and then say that at this later time t2, that arrangement of coins means 1 1. So the coins performed the controlled not gate, right? No. You did the controlled not and reinterpreted the coins by doing another computation to map the coins' state onto the result you worked out.


"I think that the criterion of intention as a condition for something to be a simulation is crazy." <- hmmm .. sort of see what you mean, but ..

Simulations are simulations OF something - they ahve a target, and they're aimed to provide an enviromnent which reflects some other situation or system.

It follows that one system (the simulation) running and presenting itself sich that it's similar to some other system is coincidence or even accidental unless the link is made with the system it's a simulation of.

Maybe that's what's missing - what is this a simulation of ? If there's isn't any target, then it's not really a simulation. If there is, then there's an intention, and to me it doesn't seem so daft that that is part of the definition.

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