Disclaimer: I started writing this in hopes it would help put me to sleep. It didn't work. Read with many large grains of salt. I like to occasionally engage in verbal fisticuffs on the internet, because my life isn't stressful enough and my blood pressure needs to be higher. And above all else, the differences between these four things: belief, opinion, fact, and hypothesis (non-scientific), are by far the most aggravating things I encounter. Let’s break it down one by one.
Beliefs
Beliefs are the trickiest because we like to say, "I believe" to a lot of things that aren't beliefs but are in fact opinions or hypotheses. For instance, "I believe man will go back to the moon." or "I believe Justin Timberlake should just join SNL." The first statement is based on facts (hypothesis) and could change if the facts change. The second is just a simple, albeit obviously true, opinion. We'll cover those later.
Beliefs of faith are the true beliefs. They are the things we hold to be true either in the absence of evidence or contrary to the evidence. These are things like "I believe in God" or "I believe people are inherently good" or "I can't believe it's not butter." There is very little chance that any amount of new information is going to change these beliefs one way or the other.
True beliefs don't belong in any type of argument that isn't directly about those beliefs. If you want to debate the nature of God, do it on your own time with other people who believe in God.
Otherwise, it's rude to come at someone with a belief statement, because it's literally saying that you don't CARE about their evidence, logic, or rhetoric. It's the internet equivalent of plugging your ears and going "lalalala I can't hear you." So, it is important that if your statement isn't actually a belief on faith, but an opinion or hypothesis in disguise, you shouldn't start it with "I believe."
Opinions
Someone wise once said, "Opinions are like assholes. Everyone has one and most of them stink." I assume this was said before modern hot water showers, because if your asshole regularly stinks you should probably either seek a doctor or bathe more often.
Opinions are, and only are, subjective statements. They are your own personal judgement about something or someone. Here is a list of opinions:
1. Roses smell good.
2. Pineapple on pizza is gross.
3. Going to the beach is fun.
4. Books are boring.
5. Purple is the best color.
6. I believe Justin Timberlake should just join SNL.
By their nature, opinions are generally unassailable. They represent your subjective experience of reality. There is some wiggle room for convincing someone that their subjective experience is wrong or at least incomplete. Expanding someone's experience might change an opinion. Maybe the only books you've read were for school and I could introduce you to a book I think you might like. But it's very unlikely I'll convince you pineapple pizza is gross you soulless pineapple loving heathens.
So why are opinions a problem? Well, because a lot of people like to dress up hypotheses or beliefs of faith as opinions in an attempt to make them unassailable or to disguise them. They inevitably start such statements with, "In my opinion..." Which is really a good warning sign, because if you have to state that something is an opinion it's practically admitting that it probably isn't. Here are some examples:
1. In my opinion, climate change isn't real.
2. In my opinion, recycling isn't worth it.
3. In my opinion, eating meat is bad for [you/environment/soul].
4. In my opinion, Bigfoot exists.
Notice how, by tacking on "In my opinion" to these statements, they no longer require any evidence to back them up. If I were to say, point out that temperatures are going up or that recycling saves tons of landfill space or that animals are tasty, it doesn't really matter. The instant rebuttal is, always, "Well, everyone's entitled to their opinion." If I point out that there's no evidence of Bigfoot existing, same response.
So... don't do this. It's not much different than the belief statements, it simply shuts down that line of an argument. I find it much ruder however, because it is sugar-coated attempt to try to appear reasonable around a massive dose of bullshit.
Facts
Facts are easy. They are the things that are. Objective statements that... wait, who are these people? Oh god, who let the philosophers out of their cages! I just wanted to have a nice peaceful discussion without having to deal with the subjective nature of existence blah blah blah. Where's my stick...
[Ten minutes later]
Okay, where were we. Right, facts. This is simple stuff like "the earth is round," or “water is wet” or “philosophers suck.” 2+2=4. Gravity pulls things together. Magnets, how do they work, etc. Basically, anything that you'd use for evidence to support your side of an argument.
Of course, facts are not nearly as solid as we'd like sometimes. Here are some common things I encounter:
1. Anecdotes are not data. Whenever you're talking about larger populations or "things in general", then any statement that starts with "I have a friend..." is pretty much right out. Individual experiences are not generalizable, no matter how many of them you have.
2. Invalidating others' experiences. "Hey, wait a second, you just said up there..." Yeah yeah, I know. There is a difference though, and it's important. If you're making an argument that something doesn't exist (usually one of the -isms, racism sexism etc), and someone says well no I experienced sexist behavior yesterday... then that's valid evidence against your point. It doesn't need to be generalized in this case because it's a question of existence.
3. Misusing statistics. Oh boy, I could write a whole entry just about this. Maybe I will someday. Statistics are evil, there are many ways they can lie. From sourcing, to calculation, to interpretation, anyone can make numbers say nearly anything they want. But there are some things you can do avoid the pitfalls or defend yourself against bad-faith number crunchers. To the sub-list!
A. Whenever comparing the incidence of something in subgroups, let's say Oscar nominations by race, then you always must look at the relative sizes of the populations. 60% of something going to one subgroup isn't very odd if they make up 60% of the population. This cuts both ways. If a group comprises 25% of X but 10% of the population, that's noteworthy even if it's only 25%. And of course, if a group makes up 10% of the populations but 0% of the nominations, then maybe you have a good point.
B. Get/demand multiple sources. This is especially important if the source isn't a government study or is from a group with a conflict of interest. Obviously, this isn't always possible, but if someone only gives you numbers about animal deaths on farms from "I Like Eating Tasty Animals International" and refuses to back up their numbers, you're perfectly in the right to question them. If you can't find multiple sources yourself, be up front about it.
C. P Values. If someone gives you a P Value and they don't have a Ph.D. in stats, just walk away. It's not worth it. If you don't have a Ph.D. in statistics, don't use them as evidence. Find some other measurement.
D. Over-controlling variables. This one is probably a bit less common and probably belongs in that other entry I'll never write. But here goes. If someone says, "When you control for X, Y, and Z, the effect of A goes away.", but one or all of XYZ could be caused A, then they've lied to you. This comes up a LOT when talking about things divided by subgroups. Income gap; the intersection of crime, poverty, and race; education, wealth, and race/age/gender. Just be careful and if they can't give you an actual list of the things controlled for, assume bad-faith. And of course, don't do it yourself.
It is important to point out that facts are often argued and that's fine. Our entire legal system is based around 12 people deciding what the facts of a case are.
When arguing facts though, it's important that you actually argue the facts and don't fall into the trap of turning them into opinions or beliefs to shore up your argument. And the burden of proof almost always falls on the person making the more extreme statement or interpretation.
Hypotheses
Okay, first off, I'm not talking about the scientific definition of hypotheses. So please, no hate mail. Ha, like I need to worry about hate mail.
No, these are things like informed beliefs or applying logic to evidence. They are often best summed up as "I think" statements. Examples, as always:
1. I think this will work.
2. I think we'll go to the moon again.
3. I think raising the minimum wage does more good than harm.
4. I think lowering corporate taxes has little effect on poverty.
All of these have an element of the unknown and some facts that can be interpreted for or against. In this way they are sort of like a scientific hypothesis. But it's not rigorous, so get off my back hypothetical angry person.
Like facts, it's important to not let them slip to opinions or beliefs of faith. However, unlike facts the burden of proof lies solely with the person making the statement, no matter how mundane or extreme.
Be prepared to bring facts and logic to back up your hypotheses and be willing to hear out counter arguments. But also, be on the lookout for people who might try to use their own opinion/belief tactics against a hypothesis or possibly even accuse you of it. If you say, "I think" and give evidence to back it up, don't accept a rebuttal of "Well, that's just your opinion" quietly.
Conclusion
Don't do the bad things. They're really tempting and we all fall into the traps sometimes, but you should always try to be debating in good faith. And if you encounter someone trying to engage in the various naughty strategies, call them out for it and if they get worked up or refuse to debate in good-faith, just disengage. It's not worth it. Or find a way to punch people through the internet.