True knowledge exists in knowing that you know nothing

I wouldn't say anything about "true" knowledge, what does that mean, anyway?
But I would agree that such a statement is a basic step in maturing your thinking process.Try not to take it literally, though. The statement isn't meant to be taken literally, and that leads to being silly.A wrong, but pervasive definition for the word "know" is that it means "being absolutely true about reality."
This is the issue that the statement is attempting to correct.Knowing that anything is "absolutely true about reality" is currently impossible.
It's impossible because reality doesn't come with answers at the back of the textbook.
There's no "ruler of reality" where we get to check our measurements and verify them.All we can do is look at the information around us, make a logical inference based off that information, and then test that guess against more reality to see if it works or not.This brings us to the mature definition for "knowing" something.
When people say they "know" something... they mean to imply that they've tested it.This doesn't mean it's absolutely true, it simply means it worked for the test they did.
It's quite possible that their test doesn't cover all situations.
It's quite possible that they thought they tested it, but they actually didn't.
It's quite possible that they didn't test anything at all, and they're just saying "I know that!" in order to try to persuade/impress someone else.However, once we understand that "knowing" something is a placeholder for "passing a test against reality," then we can understand that we certainly do "know things." And a lot more than nothing.Otherwise, we would have no use for the word "know" and need some other word that means "I've tested this..." as opposed to "I just think this..."
It's easier to just use the existing word "know" to represent such tested-things and to simply understand it's limitations.Math is an absolute idea.
But that's because math didn't come from reality.
Math is made up. It comes from definitions.
That's why there's only 1 answer to math issues... because there's it's based on axioms. Axiom is just a special math-word for "I made this up, and that's the way it is!"However, Science understands that the word "know" has to do with testing-against-reality and that everything-we-know is only tentatively held based on the information we have... therefore it is all subject to change if that information-we-have is ever expanded into new things.All Science understands this.Physics - if you don't have error-bars on your graph, if you don't understand what a 5-sigma-error-rate is... then you're not doing physics.
These error-ranges exist because we understand that any and all measurements we take have some sort of error associated with them.
If the numbers you're putting into your perfect-math-equation have error ranges.. then the number you get out of your perfect-math-equation will have error ranges.Engineering - if you don't have a SF (Safety Factor) included in your calculations, then you're not doing engineering.
This error-range exists because we understand that any and all equations we use are based on the information-we-have-available. If they were absolute, we wouldn't need an SF. The math procedures that the equations use are indeed absolute (because math is made up and defined by us). However, Science understands that the equation itself as a representation of reality is not absolute (it's based on the information-we-have-available). Therefore we require SFs to give us the comfort we require.Just like Newton's equations for describing motion.
Newton's equations are not absolute. They're not even accurate.
They're only accurate enough for things that are big.The existence of Einstein's relativity equations prove this.
Einstein's equations prove that Newton's equations are not absolute and not accurate.
Einstein's equations are simply more precise. They are more accurate.Science understands this.
Science understands that Einstein's equations, although they are the most accurate we've been able to figure out so far, are likely also not absolute and not accurate.Because they, as well as everything else in Science, are all based on the information-we-have-available.
And we know that the information-we-have-available to us is not complete.
We know that there is no answer-section for reality that will simply tell us how things "absolutely" are.Science is very well aware, and is specifically designed to account for the idea that "true knowledge exists in knowing that you know nothing."But Science just matured their definition of the word "know" from meaning "absolutely correct" to meaning "correct as far as our tests can show us, based on the information we have."With this mature definition of the word "know," Science is quite capable of knowing many, many things.TL/DR: It's a great idea, but you're late to the party. Science already figured out that we know nothing and they accounted for it a few hundred years ago. In fact, all the technological progress we've made since then is based on this very idea of knowing-that-we-don't-know. From there, Science tests-what-it-can, learns-what-it-can... and continually builds from there.