Most scientific discovery comes when people realize the premises make huge mistakes and manage to correct for them, so it's not a futile endeavor. You can apply much harsher criticism to the fields of philosophy and the humanities, since at least phycisists can test and confirm their hypotheses (and mathematicians often derive the math used for the physics).
Studying math/physics doesn't literally mean that you know math/physics, but merely that you're less ignorant of the topics than the rest of the human population.>>12606082
This applies to dialogue/discourse, but that's because there are limits to human understanding and we can often let certain facts be treated as axiomatic, despite bearing exceptions.
I would claim that the ability to substitute to convert into isn't a fact. The real fact is that describes a family/set of expressions, and is an element of this set. If you ask "why?" the closest thing to a solid answer is that this is the way we decided to construct expressions/algebra, and that said construction exists because it's the easiest for the human mind to understand.