This might be the most pedantic wall of text I have ever written in my life. When even I recognize that, given my history of pedantry, that's saying something. However, this pedantry isn't necessarily pointless. It is something that's worth keeping in mind when examining our own beliefs or critical thinking about arguments (and claims) presented to us. So, what are known truths, how do we know them? For something to be considered "true," it must also be "not false" according to the bivariance principle, which is just a principle that tells us that propositions are either true or false. This is a Boolean value. Something can't be "sort of true" or "a little false." This is a concept of deductive logic, which finds most of its use in mathematics. For instance, 2+2=4 is true, but 2+2=5 is not. We can know this for certain, no doubt in our minds. In fact, it is completely impossible that 2+2=5. It would violate the Law of Identity, since the equation would simplify to 4=5. We can also know, for instance, that there are no married bachelors, because all bachelors are unmarried by definition. This would violate the Law of Noncontradiction. Some might say that such knowledge is little more than stating the obvious, but there is a reason why mathematicians are held in so high esteem that they can develop "proofs." Technically, not even science can "prove" anything. Instead, science concerns itself with justified claims, which we will likely never know for sure whether they are true or false. It aims, not for truth, but for truth-likeness or verisimilitude. Rather than "proving" that something is true, we "confirm" that something has a "high truth value" which just means that it's probably true. Indeed, these are the sorts of claims that the bulk of modern "knowledge" really associates itself with. Do you think you know where you live? Technically, under this model, you don't; it's just that your claims about where you live are justified. There is no logical necessity that you truly live there. It's possible that you don't; that you misremembered your address, suffer from dementia or psychosis, or are a brain in a vat located in a place you've never even heard of. You can be almost certain that you know where you live, discounting these alternative explanations as unlikely, but you can never fully know that your belief about where you live is true. It just has a very high verisimilitude so that, in common parlance, it might as well be true, even if it potentially isn't. Given all of this, do you think we should be more careful about our language around these subjects? Should we replace "I know _" with "I think that _?" Should we replace "I know how to _" with "I am able to _?" How could we replace a term like "I know about _?"