Assuming of course that our theories on the way our eyes work are correct.
It's the same theory as the telescopes (and no, saying that isn't a "theory".)
it may be a valid assumption, but it is still an assumption.
And yet if it's wrong, we'll never know.
Asking "what can we know?" is a great question, so I'm glad you ask it. As is "how can we know we know what we know?" But when you hit the point where there's no way to tell between knowing something and
thinking you know it (like how there's no way to tell the difference between
knowing reality is real and just
thinking it is) it's time to stop, because a difference that is no difference is no difference. It just doesn't matter at that point.
but one day it MIGHT. and you can never be 100% certain.
By definition of the terms, I can know for certain that there's no way to distinguish between "real" reality and a perfect simulacrum (it's tautological). If it's
not perfect, then the scientific method will reveal that.
All bases are covered. The scientific method can discern all that is discernable. Nothing can discern that that is indiscernable. So what's the problem?