True Story
Information divides into two categories - opinion and fact (you can of course interpret either). There are literally millions of people who can't tell the difference. A brief look at the 'debate' on health care at the moment will demonstrate what I mean. On the one side are a bunch of people screaming like crazy monkeys about communism and Nazism, with no understanding of either of those concepts, and on the other side there are a bunch of people trying to explain where the screamers are going wrong, or getting frustrated and calling them morons.
Luckily we have many ways to tell the difference between a fact and an opinion. Here are some. Take your opinion and shove it through these filters. None of them is bulletproof individually, and there are others, but if it comes out of this filter matrix in one piece, you just might have a fact.
Filter #1: Likelihood: Is your opinion/idea possible? This bit of common sense is often codified as Occam's Razor - usually the simplest, most likely explanation is the correct one. Note that this is not always the case; but it's a good indicator. So just ask yourself Is this really likely? Is this compatible with what I know about the world? If you find yourself believing something that is entirely incompatible with everything you know about the world, you might have a problem.
Filter #2: Falsification: Can you think of a situation where your idea would be proven incorrect? This slice of genius was brought to us by Karl Popper, and is an invaluable tool in figuring out what's worthy of consideration and what isn't. The reasoning is that if you can't even imagine a situation where your opinion might be wrong, then it's not really worth talking about, is it? This often comes as a surprise to people who value being 'right' over knowing the truth (and they are legion). But if you can't prove I'm wrong, surely that's a good thing? No, it's a bad thing. Think about it. Go on; I'll wait.
Filter #3: Evidence: Do you have any actual reason for believing what you do, apart from the fact that you think you're right? If you don't think you need reasons to believe something, we're done here; you can go now. For everyone else, the best way to throw evidence at a claim is the scientific process. Religious people think science is a form of religion for adherents to believe in, but facts are non-negotiable. Religion is not science - maybe the best way to outline the difference is to say that religion is to science what opinion is to fact. There's nothing wrong with having an opinion, or a religion, and I will defend your right to have one. But it's not a fact. When religions start messing around with science, things can get very stupid very quickly (conversely, when science starts messing around with religion, you get anthropology).
Filter #4: Irrelevancy:
It happened to my aunt's friend is not evidence; the plural of anecdote is not data.
It's just something I feel is right is not evidence; expecting people to 'feel' the same way you do is arrogance.
If you can't think of anything better, this must be true is not evidence, because 'you don't know' is not in any way equivalent to 'this crazy idea must be true'. It's intellectually lazy.
You need to be more open-minded is not evidence. Believing everything you read/hear/see doesn't make you open-minded; it makes you an idiot.
You don't know everything. OK. And?
For instance, fundamentalist Christians (who are rapidly taking the place of Nazis in my go-to Example of Wrong list) think the planet is six thousand years old. The geological consensus is that the planet is billions of years old. Geologists are people who study the rocks of the earth professionally. This is what geologist means. Christians are people who think their souls have been saved by their belief in Jesus as their saviour. This is what Christian means. Which of these would you trust more to tell you about rocks? It's not rocket science, and even if it was, I'd trust rocket scientists to tell me about it. Because even if they're wrong, they still know more than anyone else.
Related: Discomfort, possibly the only case on record of a banana outsmarting a human; Portions for Fox News, some fairly simple as-yet-unanswered questions for conservatives; Reality Fiction, a modest proposal; and my page of Standard Debating Errors
Luckily we have many ways to tell the difference between a fact and an opinion. Here are some. Take your opinion and shove it through these filters. None of them is bulletproof individually, and there are others, but if it comes out of this filter matrix in one piece, you just might have a fact.
Filter #1: Likelihood: Is your opinion/idea possible? This bit of common sense is often codified as Occam's Razor - usually the simplest, most likely explanation is the correct one. Note that this is not always the case; but it's a good indicator. So just ask yourself Is this really likely? Is this compatible with what I know about the world? If you find yourself believing something that is entirely incompatible with everything you know about the world, you might have a problem.
Filter #2: Falsification: Can you think of a situation where your idea would be proven incorrect? This slice of genius was brought to us by Karl Popper, and is an invaluable tool in figuring out what's worthy of consideration and what isn't. The reasoning is that if you can't even imagine a situation where your opinion might be wrong, then it's not really worth talking about, is it? This often comes as a surprise to people who value being 'right' over knowing the truth (and they are legion). But if you can't prove I'm wrong, surely that's a good thing? No, it's a bad thing. Think about it. Go on; I'll wait.
Filter #3: Evidence: Do you have any actual reason for believing what you do, apart from the fact that you think you're right? If you don't think you need reasons to believe something, we're done here; you can go now. For everyone else, the best way to throw evidence at a claim is the scientific process. Religious people think science is a form of religion for adherents to believe in, but facts are non-negotiable. Religion is not science - maybe the best way to outline the difference is to say that religion is to science what opinion is to fact. There's nothing wrong with having an opinion, or a religion, and I will defend your right to have one. But it's not a fact. When religions start messing around with science, things can get very stupid very quickly (conversely, when science starts messing around with religion, you get anthropology).
Filter #4: Irrelevancy:
It happened to my aunt's friend is not evidence; the plural of anecdote is not data.
It's just something I feel is right is not evidence; expecting people to 'feel' the same way you do is arrogance.
If you can't think of anything better, this must be true is not evidence, because 'you don't know' is not in any way equivalent to 'this crazy idea must be true'. It's intellectually lazy.
You need to be more open-minded is not evidence. Believing everything you read/hear/see doesn't make you open-minded; it makes you an idiot.
You don't know everything. OK. And?
For instance, fundamentalist Christians (who are rapidly taking the place of Nazis in my go-to Example of Wrong list) think the planet is six thousand years old. The geological consensus is that the planet is billions of years old. Geologists are people who study the rocks of the earth professionally. This is what geologist means. Christians are people who think their souls have been saved by their belief in Jesus as their saviour. This is what Christian means. Which of these would you trust more to tell you about rocks? It's not rocket science, and even if it was, I'd trust rocket scientists to tell me about it. Because even if they're wrong, they still know more than anyone else.
Related: Discomfort, possibly the only case on record of a banana outsmarting a human; Portions for Fox News, some fairly simple as-yet-unanswered questions for conservatives; Reality Fiction, a modest proposal; and my page of Standard Debating Errors