Here’s a thought experiment that’s been confusing me for a long time, and I have no idea whether it is even possible to resolve the issues it raises. It assumes that a reality which was entirely simulated on a computer is indistinguishable from the “real” one, at least until some external force alters it. So… the question is, assuming that such a program exists, what happens to the simulated universe when it is executed?
In accordance with the arguments that Pavirta gives below me, redundant computation is not the same as additional computation. Executing the same program twice (with the same inputs each time) is equivalent to executing it once, which is equivalent to executing it five times, ten times, or a million. You are just simulating the same universe over and over, not a different one each time.
But is running the simulation once equivalent to running it ZERO times?
The obvious answer seems to be “no”, but bear with me here. There is nothing special about the quarks and leptons that make up a physical computer. If you could make a Turing machine out of light, or more exotic matter, you would still be able to execute the same program on it. And if you could make such a computer in any other universe (whatever that might mean), you would still be able to run the program on it. But in such considerations, the computer used is immaterial. A physical computer is not a perfect Turing machine—it has finite memory space and is vulnerable to physical defects which introduce errors into the program. What matters is the program itself, which exists regardless of the computer it is on. A program is a Platonic ideal, a mathematical object which cannot exist in this universe. We can make a representation of that program on a computer, but the representation is not perfect, and it is not the program itself. In the same way, a perfect equilateral triangle cannot actually be constructed in this universe; even if you use materials whose length is measured down to the atom, its sides will not be perfectly straight and its angles will not be perfectly equal. More importantly, if you then alter the representation to make one of the angles bigger, it does not change the fact that equilateral triangles have 60° angles, it simply makes your representation less accurate. In the same way, executing a program on a computer will not alter the program itself. If there are conscious beings simulated on your computer, they existed before you ran the program, and they will exist even if you unplug the computer and throw it into a hole—because what you have in your computer is not the conscious beings, but a representation of them. And they will still exist even if you never run the program, or even if it never occurs to anyone on Earth that such a program could be made.
The problem is, this same argument could be used to justify the existence of literally everything, everywhere. So we are left with several possible conclusions: (1)Everything is “real” in some universe, and we have no way of ever finding such universes. This cannot ever be proved or falsified, and also leads to problems with the definition of “everything” and “real”. (2)The initial premise is false, and only physical objects are real: simulations, thoughts and constructs are not. I think there is a philosophical school of thought that believes this to be true, though I have no idea what its name is. Regardless, there are still a lot of holes in this answer. (3)I have made a logical mistake somewhere, or I am operating from an incorrect definition of “real”. It happens.
It is also worth pointing out that both (1) and (2) invalidate every ethical truth in the book, since in (1) there is always a universe in which I just caused the death of a trillion people, and in (2) there is no such thing as “ethics”—ideas aren’t real, and that includes philosophical ideas.
Anyway, just bear this in mind when you think about a universe being simulated on a computer.
Hello. I’m Snowyowl, or Christopher if you’re interested in my real name. (Some people are.) I first discovered this site on Friday 14th August, when a friend of mine (who calls herself Kron) pointed me in the direction of the story “Harry Potter and the Methods Of Rationality”.
I don’t consider myself a rationalist, because that seems like a sure-fire way of feeling superior to 90% of the world. Also, I have realised in the past week that a lot of my beliefs and opinions are contradictory—in LessWrong lingo, my Bayesian network isn’t internally consistent. Of course, I had noticed that before now, but it didn’t seem an important problem before I read a few relevant blog posts. So no, I’m not a rationalist, and I hadn’t even heard the word until two weeks ago.
I’m a second-year mathematics undergrad at the time of writing; I had actually heard of Bayes’ Theorem years ago. I have also taken courses branching out into computing and physics. The techniques in your blog appeal to my way of thinking, since I enjoy mathematics and logic, and applying scientific methods to everyday life is a relatively new concept to me.
So hello, LessWrong! I look forward to many calm and reasonable debates!