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.