I mean, there might be a secret AI technology that is so advanced to the point that it can mimic a real human, make posts and comments that looks like its written by a human and even intentionally doing speling mistakes to simulate human errors. How do we know that such AI hasn’t already infiltrated the internet and everything that you see is posted by this AI? If such AI actually exists, it’s probably so advanced that it almost never fails barring rare situations where there is an unexpected errrrrrrrrrorrrrrrrrrrr…
[Error: The program “Human_Simulation_AI” is unresponsive]
That quickly boils down to “How do we know anything?” and the answer to that is “We don’t”. When you think hard enough about anything you can come up with an explanation why what we think to onow and believe is wrong. To get around that irl you can employ different tactics. For example, you can check how plausible sonething is. How many assumptions do you have to make for a theory? Usually, more assumptions means less plausible. And you can ask yourself " why does it matter? What would it change for me?" and the answer is most likely it doesn’t and nothing.
Well, we do know 1 thing without making at least one leap of faith, courtesy of Descartes:
If nothing existed, there wouldn’t be anything to have these thoughts. Therefore, since I’m thinking, there must be something that exists, and at least part of that is me. It might be an algorithm, a boltzman brain, some weird universe of thought, whatever. I might even be this singular thought and what I assume to be my memories and nothing else exists. But I know I exist in some kind of way.
Beyond that, you need to make assumptions, like whether reality is logical, whether your senses and and memories have any relation to reality, and so on and so forth. It makes sense to assume these assumptions are correct, but you can’t know or prove they are true without relying on other assumptions that you can’t know or prove independently either. Heck, without assuming that reality is logical, the concept of a proof doesn’t even exist. You can choose to reject those assumptions, but that’s a useless philosophical deadend.
Which is why someone answering “Believing is what you do in church, we’re in the business of knowing!” to a sentence like “I believe I’ve seen this before” annoys me a bit, since you can’t know anything useful without believing a bunch of stuff first. If someone’s going to be pedantic about that choice of words, so can I.