I think there might be a proof something along the lines of 'for any truth that can be expressed within a system there will be truths that can't be expressed within that system'. Something to do with Godel's incompleteness theorums... But I don't really understand them (or whether his proof is properly or improperly applied to issues of semantics).

I'm pretty sure it is uncontroversial that there isn't much (probably isn't anything) that is complete. Maths isn't... Logic isn't... I'm pretty sure you won't find a science that is (or they wouldn't still be doing it lol). Wiki certainly isn't lol.

I think there are a whole range of considerations that come into play with respect to how much one should be inclined to believe a source. I know a lot of people who start out with Wiki (which is actually pretty good as far as it goes, I think, though not perfect, of course, and you do find some doozy's sometimes) and then progress from there. Most people have 'confirmation bias' which means they tend to seek out evidence that confirms their views rather than seeking out evidence that would disconfirm their views (which is a kind of logical fallacy in data collection), however. I guess that is the thing. If we get a random email and we fairly much agree then we are inclided to take it at its word. Whereas if we get a random email and we fairly much don't agree then we aren't so inclined to take it at its word.

People have tried to systematize the things that should indicate that a source is reliable compared to a source that is unreliable. It is kinda hard to systematize... People are especially keen to get that right when it comes to consumers finding health information on the internet... Issues with data collection... Issues with assigning high weights to sources that are outliers rather than sources that are representative of expert opinion and so on and so forth...

It is kinda interesting how one person can think they understand the politics / economics distinction just fine - but that other people can either not see the distinction so clearly or have quite a different distinction in mind. I'm used to 'PPE Programs' - which is to say 'politics, philosophy, and economics programs'. Where do you draw the hard line between politics and economics? Hard to say... I wouldn't like to attempt a definition...