It's an interesting thought - this simulation theory. We cannot rule out the possibility of reality being a simulation.

The key question is ''how can we know whether reality is "real" or just a simulation?

To answer this question we can examine dreams. When in a dream state one doesn't realize that one is dreaming - everything feels real until you wake up in the real world.

Can there be something analogous to that in reality? Has anyone ''awakened''?

but an enormous number of simulations won't increase the likelihood of other things being simulations. Even in a universe replete with simulations each and every simulation must be composed of parts which are constituitive for the possibility, but insufficient separately. The number of parts is always greater than the number of simulations. — jkop

According to known physics, our descendants will be able to simultaneously simulate many trillions (surely an underestimate) of universes simultaneously on a single device. They will of course be using quantum computers.

How would an exercise in counting infinities be a reason to believe that reality is a simulation? — jkop

It renders the probability of us not being simulated zero, to any degree of accuracy.

Of course this is all predicated on the idea that our descendants will simulate us. They won't!

Lucid dreams are people knowing they are dreaming. Also reality is subjective in this case. Our reality is real, to us. But there would be another reality that's real to the simulators or other simulations.

simulation theory — Grey

Just to be pedantic for a moment. 'Simulation' does not involve a clone, nor an identical copy. Simulated sex, for instance (to lower the tone momentarily) is nothing like the real thing. Simulation is something which imitates in an unspecified number of respects the thing or activity simulated. The 'unspecified' part makes me worry at the vagueness of the concept, which provides a get-out close if there are details uncopied in the simulator.

This of course applies both to 'simulation theory' and to the Deutsch idea of quantum computers simulating life. Simulation is limited-in-some-way imitation.

Yeah I love the idea of that. I don't know why people tend to assume humans simulating human life. I guess that is the easiest and most practical thing to jump to but I like to think about fun stuff simulating us.

The argument is that if there are more simulated worlds than there are non-simulated worlds then you're more likely to be in a simulated world than a non-simulated world. — Michael

Looks like it contains fallacies of ambiguity, such as two different senses of 'world' used in one sense: worlds you could be in. Or different senses of 'to be': as in to be in a world, or to be represented in a world etc..

The obvious question here is ''how do we know we're a simulation or not?"

We can't.

Exactly, which is why, until technologies can answer the question we just wonder and think.

Some would call it a futile endeavor because the question is unanswerable. However I hesitate to dismiss human ingenuity - may be someone in the future may develop a clever way of detecting simulation indicators

Some would call it a futile endeavor because the question is unanswerable. — TheMadFool

There is a decisive answer to the question whether we're brains in a vat, recall. We're not brains in a vat, because if we were, then not only would our lived world be a simulation, the words 'vat' and 'brain' would not refer to real brains and vats either. Likewise, we don't live in a simulation.

the words 'vat' and 'brain' would not refer to real brains and vats either — jkop

Only if the causal theory of reference is correct.

There is a decisive answer to the question whether we're brains in a vat, recall. We're not brains in a vat, because if we were, then not only would our lived world be a simulation, the words 'vat' and 'brain' would not refer to real brains and vats either. Likewise, we don't live in a simulation.

The irony here is that this proof against us being brains in a vat was a disproof of realism, as realism entails that it is possible that we're brains in a vat. And given that the brain-in-a-vat hypothesis is a problem for the realist, this answer isn't a satisfactory answer at all. The realist needs for it to be possible that we're brains-in-a-vat, just not the case that we are.

We're not brains in a vat, because if we were, then not only would our lived world be a simulation, the words 'vat' and 'brain' would not refer to real brains and vats either. Likewise, we don't live in a simulation. — jkop

Not so! The Boltzmann brain, or rather a Boltzmann person, would simply have false memories, and the words "vat" and "brain" would refer to the real things.

The issue is that for many cosmologies, we are vastly more likely to be BBs than real people. There is actually a large physics literature on this problem, and a surprising level of disagreement. It's not a problem that can be just swept under the carpet. Some physicists think it is a big enough problem that our current consensus cosmological model (Lambda-CDM) must be wrong!

Of course, we don't know that purpose yet but all the evidence is there to make that assumption. — Grey

???

Just what evidence are you talking about?

But I really like playing with the idea currently that the entire universe could cease to exist for years on end and we would never know. If you think about it, if reality is a simulation, the simulation could crash and everything would cease to be. But if the simulation has save points and is rebooted at the time it crashed we wouldn't notice anything. It's a fun idea to think about I guess. — Grey

The simulation would be part of the universe, no?

I kinda like to think that if we, in the 3rd dimension can create 2 dimensional simulations — Grey

A problem with this is that we can't actually create anything two-dimensional.

The Wrong Starting Point

You are beginning with the wrong mindframe. You should have the perspective of "Data vs. Theory". If there is no data, then any theory is just as viable as the next (and the theorists shouldn't argue with one another - as they still do - not being aware of my premise). In a special case, there may be a lot of good date (verified knowledge), but YOU may be completely unaware of it, and you will be creating simulations that have already been explored and have been deemed unreal (though entertaining).

The Value in Creating Uninformed Simulations

The only value in creating uninformed (meaning lacking an adequate awareness of existing verified knowledge) simulations is in the exercise of your imagination. Why is such exercise important? Because it is a critical phase in science - the phase where you are considering possibilities (which is the phase that precedes selecting which possibilities to spend time, expense, and energy investigating further).

there is a very interesting take on this issue here. probably the best approach so far : https://www.infopadd.com/article/the-fact-that-we-are-living-in-a-simulation/1656-4400

Well, it's not exactly parsimonious, and lends itself to a regress ...



Programmers of a simulation can do whatever, beyond the usual cheat console in some games.
Reliability goes out the window, which undermines our efforts to understand the world.

_{Guard In Video Game Under Strict Orders To Repeatedly Pace Same Stretch Of Hallway (The Onion, Oct 2014) :)}

Something that interests me too.

My take on this is we can't disprove that we're in a simulation. Suppose Mr. x lives in a universe u simulates a universe v and Mr. y is in v.

y would need to be able to come out of v and exist in v, like x, to realize it is in a simulation.

However, y's sense organs are designed for universe v and there's no guarantee that these senses will work in universe u.

I think that's one of the most basic problems for Mr. y (us).

That means we can never know if we're in a simulation or not.

So, all we're left to do is to play around with the idea without achieving anything substantive.

Look at nature. Everything acts with purpose. — Grey

If you've justified this in the thread, I didn't see it. Please and kindly direct me there.

Otherwise, is this just a presupposition? If it is it's a remnant of Greek biology some 2300 years old, and either that age or got from antecedents far older. As such it cannot be correctly understood in modern terms without a good deal of qualification, including why the Greeks said it in the first place.

Or it's just a modern proposition, posited because it echoes something that sounds good, without actually testing to see if it is in fact reasonable. Let's suppose this latter case. What does "Everything acts with a purpose" mean? What is a "purpose," here?

Everyone makes a good point about a 2nd universe. Even if you presumed the universe was contained in a sort of bubble (like a more durable but equally pliable bubble of sorts) you could expand that to include multiple bubbles to account for the multiverse theory as well as the debate over expanding vs shrinking universe. In any event the bubbles would still require of bowl of some kind to hold them all thus the need for at least one other reality besides the simulation.