This begs for a definition of knowledge. It seems like you view knowledge as absolute certainty that a proposition is true. This is not feasible out of the realm of definitions. For instance: we can know for sure that all triangles have three sides. But when we move onto the natural world, knowledge is obtained through induction, deduction and abduction (the scientific method, see Popper, The Logic of Scientific Discovery), which does not warrant absolute certainty. Based on this, I define knowledge as: a set of hypotheses that allow for prediction or control of interactions in reality. This knowledge is progressive and cumulative.

But then you move on to belief, which is not a subset of knowledge. It just means accepting something as true. Ideally, of course, belief and knowledge would be perfectly superposed. And if anyone values this desire the best service you can provide is to question the justification for one's beliefs. But do not assume that all beliefs grant knowledge, for the latter is a subset of the former. I encourage you to keep inquiring people about their beliefs, I think this kind of dialogue is our only hope for society.

Descarte's "cogito ergo sum" is a statement of absolute certainty, i.e. that cognition is proof of existence. Your "no one knows" position aligns more with Berkely's solopism, (a.k.a. "idealism" ) which rejects materialism and opines that ONLY perception is real; i.e.nothing material actually exists independent of it being perceived (Edward Sapir adds a footnote) . . But that is all a trip down philosphy memory lane. Modern thought moved on.

I believe that your thinking is still tied to the Newtonian "clockwork universe" paradigm in that it is based on an assumption of absolute certainties. Frankly, that is passe. Probability replaced certainty in modern thinking with the advent of quantum physics.

So, loosen up, abandon absolutism, and accept things as functionally/operationally true, given some level of probability. We operate on heuristics rather than certainty.

Let your angels abandon their head-of-a-pin dance floor.

Uhm, yeah I sounded a bit like a preacher, but gosh, it is inevitable XD.

PS. I'm not preaching though, just wanna share some memories of me being a freethinker X)