So are you saying seeing is required to believe in something?I am really tired of seeing people equivocating between seeing and empirical evidence.
Empirical evidence is not, and never has been, the same thing as “seeing”. I can see something without having empirical evidence for it. For example, people have visual hallucinations and dreams. With the use of drugs, we can artificially induce all kinds of visual stimuli without something (other than the drug and it's interaction with one's brain) actually being there. In fact, even viewing a movie involves seeing things which, in some sense, have never actually existed*.
Additionally, we can have empirical evidence for something without seeing it. I’ve never seen what a sunrise looks like from the surface of the planet Mars, but we have good empirical evidence that it occurs. Likewise, I’ve never seen a capybara, but I have strong empirical evidence that capybaras really are rodents indigenous to South America. Giant squid have never been directly observed while alive, but that we have giant squid carcasses is good evidence that there are also living giant squid. For an even stronger example, I’ve never directly seen an electron, but we have good empirical evidence for their existence.
It’s certainly not required that we see something to believe in it, at least not in the sense of logical necessity. It’s also not necessary that we have empirical evidence for it.
But there is something else which is true. For the proper epistemic grounding of a wide range of claims**, empirical evidence may be required. And if we are cognisant of this detail, we may find ourselves unable to wilfully change our minds on a given issue without proper evidence. Otherwise, we’re just being gullible.
--------------------------------------------------------------------------*Note that in both hallucinations and in the case of cinema, you are actually seeing something that exists. With the hallucination, you are seeing a real hallucination. And in the case of cinema, you are seeing a real movie. But Darth Vader presumably does not really exist, even though you can view a representation of him in Star Wars. In that sense, in which you could be mistaken about what you think you are seeing, you can see something that does not really exist.
**This surely cannot be true of all claims. If it were true that all claims required empirical evidence, we'd find ourselves in an infinite regress. Why? Because every proposition a would need to be justified by another proposition b, itself justified by a third c, and so on. By having certain kinds of reasonably basic assumptions that can be agreed upon by all relevant parties, we can cut off this infinite regress. That may not be a satisfying solution, but the only alternative is strong philosophical scepticism; i.e. the position that we cannot know -- or even infer -- anything at all. It may be additionally argued that some propositions are best justified in non-empirical ways. For example, mathematical propositions are, arguably, best justified in virtue of a mathematical proof. Our internal emotional states are perhaps best inferred by internal reflection rather than empirical investigation of the world external to ourselves. Additionally, David Hume's famous "is-ought" dichotomy gives us strong reason to think that empirical investigation is incapable of fully answering moral questions; empirical investigation can allow us to infer what is, but not what we ought to do.
