Previous I mentioned how difficult it is to win an argument, partially because arguments can always be boiled down to extremely basic principles that you essentially have to assume. At some point, somewhere, you have to make use of facts and assumptions most reasonable people consider self-evident., and if they get disputed there’s not a whole lot you can say otherwise. It’s not hard for a person to quickly turn any debate into one of philosophical principles, and since most of us are not philosophers (thankfully), that can make it hard to resolve.

Example:
Dude1: It’s pretty obvious that we need universal healthcare in this country, I think.
Dude2: It’s not obvious at all! What evidence do you have that universal healthcare would work better than the system we have now?
Dude1: Well, there’s Study1, Study2, and Study3, which all suggest that our system is deeply flawed.
Dude2: You’re not an economist, and have no formal training or study in that area – how can you possibly verify the truth of what they’re saying?
Dude1: Well, it’s been widely quoted by…
Dude2: By people pushing their agenda, same as you!
Dude1: You’re a dick!

~fin

The world we live in is super complex, and there’s no way for one person to understand even a fraction of it. There’s no way to make our way in it without an enormous number of assumptions about the way things work. If you dispute one of them, it’s very difficult for a person to call you on it (though they will, in fact, call you a dick).