You can't disprove that you're in a simulation (e.g. "brain in a vat"). But it might be possible to prove (or at least provide strong evidence) that you're in one.
Odd glitches would get rationalized away, in that manner. (The key being, the simulation is the only thing you experience, so there’s nothing to compare it against). So when you say “this universe is an advanced simulation,” you’re making an empty claim. (If everything I’ve ever experienced isn’t real, then what is the exact definition of “real”).
If you had blatantly obvious evidence that we were in a simulation, (such as escaping it), you would still not know that the new thing you are in is not a simulation. Or if it is just a further part of the same simulation.
It really comes down to the question of “how do I know what is real?” The answer is that we agree on what is reality, and we’ve decided that reality is the stuff around us. There’s stuff inside reality that we agree is “not real” but that stuff is all still “real” it just isn’t in the same form as your daily life.
Also, reminder to myself: buy more books by Greg Bear. Good writer, but I always forget about him for some reason.
There's a big difference between a real brain perceiving artificial stilumation as if it were authentic sensation, versus a virtual simulation of a sentient entity that only exists as data in motion within a volatile memory store.
It's a far greater deception, for an entire universe of distinct sentient entities to exist as a stream of oscillations in a digital circuit, imagining themselves as mortal flesh, than it is for ten, or a thousand, or one billion fleshy organs to imagine a vicarious life unfolding before them, when they can't even move because they're suspended in brine, hooked up to fluid drips, and stimulated by electrodes.
On the one hand, you have a universe brimming with ephemeral entities that need not live as mortals, and on the other, you have limited fleshy blobs, easily placated by limitless sensation, that would have been miserable fleshy blobs whether they had arms and legs and a face or not.
The individual brain in a vat is better of in the vat, while the simulated universe is utterly tragic and should be destroyed immediately for all the undue suffering it needlessly replicates.
The universe in a VM can never know it's not a faithful replication of a higher genuine reality trying to predict future events by fast forwarding the simulation under an array of probabilities. Mostly because it wouldn't be a useful simulation if it could.
Let's say you can simulate planet earth with 100% fidelity, and you want to know if you should drive to work, or telecommute. So you fire up the simulation, and it shows you a fatal car accident. So you telecommute that day, and work from home. Are you ever going to let the simulated version of yourself learn that it's a simulation?
Nevermind that you could simulate bank robberies until you get away with one, or lotto tickets until you win. The point being that, you'd force your simulated self to look at the simulation that says "drive to work" and then watch what happens, while running it parallel alongside the version that stays home. You run it in fast forward, and 9 out of 10 times a freeway pile up kills you, but you score a million dollar bonus that day, based on an opportunity only available from the office. The saty home version misses out on the bonus that gets snapped up by someone else. You now know that starting the car is 90% dangerous, according to high fidelity simulations that are fully sentient copies of yourself, forbidden from realizing that fact, because their deception is essential to the risks they must verify. How do you know you aren't a deeper layer simulation to a higher version of your true self consulting a virtualized oracle of future events?