So I was in an argument about a week ago about how I can't say that this tree is a tree, because someone else could call it a giraffe, and if I were to say, no, it's a tree, they could say no I think it's a giraffe because I've grown up with perceiving that as a giraffe, and been taught that the word to describe this thing is giraffe. Now while this is obviously stupid, I realized you can't even argue against it. How can I say that this photo is in fact a photo? According to him, it could be a cantaloupe and I couldn't say it isn't, because he perceives it as a cantaloupe/has grown up thinking it's a cantaloupe. Then my friend started jumping in trying to say that I by saying that no, it's not a cantaloupe, it's in fact a photo, that I'm trying to disprove the Theory of Relativity. Now, maybe it's just me, but I'm pretty sure that the Theory of Relativity deals with space-time and the speed of light and the principle of relativity, not perception and what you perceive, so he's completely wrong. The whole argument ended when I got frustrated because I couldn't argue against their claims. Like, it ended with him saying, how do you know that these words on the wall aren't Spanish? I said because they are English words and they don't exist in the Spanish language. He then states, well what if I've been taught that English is called Spanish and Spanish is called English, and that I think those words are in the Spanish language? I mean, you can't argue against that, or at least I couldn't think of something. Also, he started saying that I couldn't prove that he couldn't see infrared, though obviously I can't. I tried to state that it's up to the person stating something like that to prove it, and then he said, why is it? He said it wasn't up to him to prove anything. I said that's how arguments work or something like that, but that's not a good argument for why.