I was thinking about this a bit recently. Now, as a disclaimer, I am not particularly well-versed in philosophy or anything, so chances are I'm either categorically mistaken or echoing a well-known idea.
My thought was this: something that is fundamentally unknowable is also fundamentally irrelevant. Particularly, something only matters if it has some effect. This leads to two cases: it either has an effect, and is therefore measurable, or it does not have an effect and therefore does not matter.
Now, this only applies to problems that are fundamentally undecidable--if it's just practical limitations (say technological shortcomings) then they could have an effect that we just can't reasonably trace.
But the idea of living in a perfect simulation that behaves just like the universe? From our perspective, that is not different from the just living in the universe at all. Now, if we could measure a difference, it could be important, but lets take the premise that we can't: now thinking about the universe as is or as a simulation of the universe as is is equivalent. So in either case the simpler model--no simulation--is, in essence, correct.
The same applies to a religious straw man--the god who does not affect the world at all. If the god just makes the world behave exactly the way it behaves, it may as well be taken out of the picture, mathematically cancelled (in a sense).
Sounds similar to Pierce's thoughts on pragmat{i|ici}sm:
Consider what effects, that might conceivably have practical bearings, you conceive the objects of your conception to have. Then, your conception of those effects is the whole of your conception of the object
Other than Pierce, there are other thinkers who were pragmatists of one variety or the other that had a big influence on american thinking like Ralph Waldo Emerson, John Dewey, Reinhold Niebuhr and William James.
I think we'd need to distinguish "scientifically irrelevant" from "humanly irrelevant".
Scientifically, discovering that a god created the universe and let it be (the disinterested watchmaker) has no bearing on any future experiments.
Psychologically/sociologically, discovering that some god exists would change humanity forever. Even if the god couldn't be interacted with, the level of religious fervor would rise to unimaginable heights.
Discovering we are simulations living in a matrix [every neutrino has a serial number on it!] might drive people to drastically different behavior (suicide, risk taking, etc.) even there may not be a measurable difference in the simulated and virtual reality.
Basically,
human society with irrelevant knowledge of universe != human society sans knowledge
But if we could discover that we live in the matrix or at the whim of some deity, it would mean that that fact had some effect on the world. Even a tiny non-zero effect could be amplified, like you explained, to have gigantic repercussions.
However, I was only really thinking of fundamentally unknowable things. That is, my argument is basically (in mathy notation) `∀x: ¬disoverable(x) → ¬matters(x)`. That is, if you can know x, I've said nothing about it. All I'm saying is that if you cannot discover something to be true, it cannot have any effect on you.
The contrapositive is also very important: `∀x: matters(x) → disoverable(x)`. That is, if something could have an effect (like your examples) then it has to be discoverable.
Since your main premise is that disoverable(x) is true--e.g. we can somehow find this out--my statement does not apply (or, rather, thanks to the way implication works, it's true regardless of what effect x does or does not have).
Now, if we fundamentally can't prove whether we're living in a simulation or not, somebody could still convince the human population that we are and cause the same effects you're mentioning. However, the beautiful thing here is that this could happen regardless of whether we actually are in a simulation or not (since the premise is that we can't tell), so the truth of the fact doesn't actually matter.
I think your making a few logic errors there. There would have to be some effect to prove either of those theories and that would be scientifically relevant. Just for example the first may be say seeing into the heavens which would raise questions about what laws of physics governs theres.
In other words "knowledge of the universe" == "knowledge" and there is no irrelevant knowledge as the universe is everything.
This is a fundamental property of the scientific method: that which is untestable(what you call unknowable)is inadmissible in reasoning. This is also the materialist view you are expressing (and my own view as well).
Yes, many feel this way. After thinking about it, I have found it a bit of circular reasoning, though. When you use a phrase like "fundamentally unkowable" you are using the definition of the thing you wish to explore, simply stated another way. You begin with saying "I can only reasonably take action on things that I know about in a scientific sense." then you point out that when dealing with things like simulations, they exist outside the world of empirical data, ie, scientific knowledge. You ask the question something like "But if I am unable to determine something empirically, what sort of useful action could I take?" and finally end up with "I can only take action with things I know about in a scientific sense." Full circle.
The problem is that the premise is demonstrably not true. We take action all the time based on things that have nothing to do with science at all. You watch a movie about dogs and decide to buy a dog. I tell you a story about a starving kid in Africa and you decide to send him some money. Science enters not into the picture one bit. Humans are not robots.
Here's a thought experiment. Let's say you are living six thousand years ago and about to go die in some epic battle. I am able to visit you from the future, but only you, and only appearing as somebody of your time. I tell you something like "Yep, you're all probably going to die today, but I'm from the future and I want you to know that your death has major meaning and changes the future for mankind in ways that are tremendously good. Thank you."
So you go out into battle motivated and kill a few more of the enemy. Perhaps before the battle you stand up on a rock and tell everybody you know that people from the future will one day remember their names in glory and that what they do here today is a tremendous victory for mankind. You have received information and are acting on it that is completely outside your ability to verify. It's completely outside the ability of your entire culture to make sense of or verify. Yet it has a major, positive impact. The people listening to you, based on science, should not accept what you say. Yet this is not the way it plays out.
Let's run through the scenario again, only this time I lie to you. In actuality your death means nothing. Perhaps I'm not even from the future. Perhaps I came from across the valley. The thing is, it makes no difference at all. The fact that it had an emotional and very real physical impact on the world means that it is something worthy of our consideration as humans -- not as scientists, but as humans.
You might feel like I am going down the road of "religion may not be true, but it has emotional impact on people, therefore it is good." but I am not. What I'm saying is that there is a class of information exchange and reasoning that has nothing to do with science yet is useful and irreplaceable in our lives. How you choose to go about dealing with that class of information and reasoning is your own business, but for me at least I've found the chain of reasoning that sounds like "things I cannot scientifically prove are not worthy of my time" to be unworthy of pursuit. It seems woefully incomplete when compared to what really happens in the world. And perhaps a bit naive. Or at least blinkered.
Just my thoughts. Thanks for sharing yours! :)
EDIT: Just to clarify, when I say "It is not logical to waste energy either believing or disbelieving in them." in the GP, I mean not worthy of my emotional energy. To me, it's perfectly normal to act in as rational a manner as possible, and to enjoy myth, being human, superstition, awe of the unknown, and creative speculation when I need to. I do not spend all of my time in either system, and it's not worth a big emotional investment to try to debate things between two such fundamentally different paradigms. I do not understand why people keep trying to do so.
My thought was this: something that is fundamentally unknowable is also fundamentally irrelevant. Particularly, something only matters if it has some effect. This leads to two cases: it either has an effect, and is therefore measurable, or it does not have an effect and therefore does not matter.
Now, this only applies to problems that are fundamentally undecidable--if it's just practical limitations (say technological shortcomings) then they could have an effect that we just can't reasonably trace.
But the idea of living in a perfect simulation that behaves just like the universe? From our perspective, that is not different from the just living in the universe at all. Now, if we could measure a difference, it could be important, but lets take the premise that we can't: now thinking about the universe as is or as a simulation of the universe as is is equivalent. So in either case the simpler model--no simulation--is, in essence, correct.
The same applies to a religious straw man--the god who does not affect the world at all. If the god just makes the world behave exactly the way it behaves, it may as well be taken out of the picture, mathematically cancelled (in a sense).
Anyhow, just a thought.