...because what it is not does not exist, and I cannot have a concept for something that doesn't exist.
This just begs the question of how you define "exists" (concrete versus abstract).
This brings us back to Quanta versus Qualia.
Does NOUMENON "exist" (since it's not "empirically verifiable" but remains logically necessary)?
...falsehood cannot be "not truth", but it is what is subjectively true, although not objectively true. Unlike what we usually call truth, which is objectively true, out of appearances.
You've highlighted another important misconception.
The "objectivity" trap (humans are fundamentally subjective).
Think of it this way.
There are a very few things that can be considered "provably true" (apodictic truth).
There are a very few things that can be considered "provably false" (logically incoherent).
EVERYTHING ELSE (99.999%) IS QUALIA (OPINION, GNOSIS).
I also see the danger of considering any knowledge as "irrefutable facts"...
That's why it's important to clearly define the very exclusive and rare scope of apodictic truth.
...because, one is always human and there is a considerable margin of error, so that what we consider "facts" can also end up being opinions,
This should never happen. Facts are always distinguishable from opinions.
...that's why I am more on the side of falsificationism and I tend more than anything to consider justified knowledge as "not refuted", rather than as "absolute truth".
I consider "justified knowledge" as "actionable hypothesis" based on its EFFICACY.
I see no utility in conflating "actionable hypothesis" with apodictic truth.
Everything exists, because nothing can not exist, because nonexistence evidently does not exist. Only there are different ways of "existing". The noumenal and the intelligible exist in a way that we cannot physically verify, and sometimes, in a non-physical way, because existing is not only being matter, it is simply being.
Yeah, I know, that's why I hesitate a lot to consider things as "facts", when it can be, after all, an opinion.
How can we distinguish facts from opinions when, as you say, what we consider to be the truth is what is "probably true"? It is always something "probable" and not certain, we are not 100% sure of anything, not even I am sure of this statement, so how can we know that what we consider facts are not just opinions? I am not saying with this that all opinions are equally probable, there are some more than others and therefore more valid, but in the end, opinions, because we cannot be sure.
I see justified knowledge as the closest we can be to objective truth, from what I said earlier.
There are only a very few FACTS (apodictic truths).
You do not know everything.
This is a FACT.
Everything you know was learned via SUBJECTIVE experience.
This is a FACT.
The sun showers the earth with radiation.
This is a FACT.
Clowns are creepy.
This is an OPINION.
The ancient Egyptians owned slaves.
This is a HYPOTHESIS based on compelling evidence.
Well, I will have to agree with that.
Zoiks!