Do you believe something that is not true? Not just unsubstantiated, or beyond the scope of the scientific method, or unreproducible personal experience, but something that is objectively false? Of course not! Unless... have you really examined everything? Everything?
This insomniac mental dump stream-of-consciousness rant is not guaranteed to be coherent. Read at your own risk.
I think it is safer to say we have degrees of certainty about things, but our certainty may not be built on a sound foundation, so some humility is probably wise whenever making any statement.
I will illustrate this by making a definitive statement:
The earth is round.
Well, an irregular oblate spheroid, but you get my meaning.
Of course, I have never been far enough way to see it as a rotating planet that revolves around the Sun in an elliptical orbit, and it looks like a flat plane when crossing the plains states in the midwestern US.
However, the people who tell me it is a spheroid, and that the solar system is a heliocentic model, can also tell me why they believe it to be so. they can explain the mathematics. They can demonstrate with experiments and measurements. They can say why the expect to achieve certain results, how the results could be in error if they are mistaken in their assumptions, and they can show how geocentric or flat earth models fail to prove their cases. I am bout as confident about the shape of the earth as I can be about anything.
Now, a common-knowledge falsehood:
George Washington chopped down his father's cherry tree, and when questioned on the matter, admitted to the deed, saying, "I cannot tell a lie."
This probably did not happen.
The source of the story is a dubious biography written for the express purpose of presenting Washington as a patriotic and moral saint of the new Republic. The story was not even included in the first edition, and is unsubstantiated in any other contemporary record to my knowledge. I am tempted to say it absolutely did not happen.
He also did not have wooden teeth. I'll say that with greater confidence than I'll say he didn't bark, much less chop down, any cherry trees as a six-year-old.
Look at the stories many people believe today. Is 'Q' right about Trump's super-secret inauguration? Is SARS-CoV-2/COVID-19 really an existential threat, and were lockdowns necessary? Does Iran have a nuclear weapons program? Is universal basic income and national healthcare a necessary solution to our health and wealth problems? Do wars create prosperity? Does firearm freedom cause violent crime? Do video games encourage murder? I say, "no," with very few caveats if any.
Disagree? Present and defend your evidence instead of calling names.
Truth is not affected by your feelings. Opinions are not equal to facts. The threat of violence by humans in response to violating human legislation is not the same as a natural consequence of disregarding the laws of physics. Cherished falsehoods remain false. Popularity or "common knowledge" carry no weight in rational discourse. A=A.
We are currently living through an era of self-righteous social justice and cancel culture abuse and censorship. The new McCarthyism is from the "left," and blacklisting is suddenly being celebrated by the Hollywood elites when it aligns with their prejudices. Principles are cast aside when partisanship gets in the way, just like how the "right" forgot about all pretense of fiscal responsibility once they held the majority. People seem to prefer comforting rhetoric, no matter how dishonest.
Next time you see someone make a declarative statement, especially if you agree, have the courage to challenge it. Seek evidence to support it. Try to disprove it. Explore your own bias and consider the potential for misinterpretation. Consider the counterarguments and alternative explanations. Be confident in your position because you put in the work, not just because it gives you the warm fuzzies.
If I can read Karl Marx, you can do some uncomfortable stuff, too. It doesn't mean you're wrong in the end, but at least you won't be as likely to mischaracterize your opponent in a debate and look like an idiot to those who do know something more. Sure, everyone knows the Earth is round, but how do they know? Perhaps you can't convince a flat earther dedicated to their ideology, but how would you prove it to yourself if you allow yourself the honesty to question your preconceptions? If you can test something as easy as that, carry on with everything else you know that is subject to the scientific method, historical records, and other means of verification. And if you are e wrong somewhere along the line, have the courage to admit it, change your mind, and carry on.
But hey, I could be wrong here, too.