Metaphysical or ontological knowledge is not subjective or delusional, but we are confined to beliefs in language and logic to see what is objective empirically at least.
Experience could show what beliefs are true if it coincides in these 2 example ways:
Action -> effect -> belief.
Event -> belief.
Even if not conscious, beliefs can be stored as patterns of action neurologically in the subconscious, perhaps not like logical possibility belief systems, but which are (like dreams) not bound by conceptual frames of I, body, time, space, etc.
Logically one cannot say, bc of language, which causal theories are true - it is very possible (depends on who you are) that causality may involve hitherto unknown (and mysterious) factors if we aren’t dogmatic.
On some very basic level this is cartesian, we believe because we are, and we are because we believe (ignore faith, ignore etcs). So what “I” really “am” goes here:
I know i exist but I do not know what is.
All things/objects are causally interrelated (figure that out for yourself).
Traditional knowledge has my body see x and name it.
Conscious aspects of belief-formation are irreducible (sorry).
The mathematical/physical is a partial account (yes im introducing unexplained assumptions. sorry)
What is the rest? - it is “imaginary” (in the dream-like way mentioned earlier) in the sense that it supersedes the I (meaning the psychological entity called the “Ego”), yet it is “real” (it is the Truth). So, it is unified/eternal.
The mathematical/linguistic seems to point at a reality that is not conscious (if assumed for whateever reason), functions as a whole, yet traps us in an eternal illusion.
G’s assumption clashes with D, which overrides it. We need to know more psychologically, eg to remove dogma/assumption on both sides if we want to have a productive discussion. So i can’t prove anything here, i can only show you the belief process around my experiences, and point out why I think it’s more elegant/effective.
The metaphysics of a true reality (mystical, based on how it was described) is much more elegant:
By minds being unified, the problems of language are avoided and shown to be related to illusion, true knowledge is possible.
Naturally such a state is not logically analyzable from the outside - a weakness.
The mathematical/logical becomes a medium for allowing us to function in a shared illusion (or Truth.. ha), rather than saying some odd mathematical realism or whatnot.
The subconscious is merged with the conscious. Action is possible because thought, perception, feeling, and volition are all aspects of a unified Truth beyond, primarily, self/time (well yes and suffering - no im not a buddhist haha). My thought patterns are usually influenced by subconscious memories of experiences, or logical reasoning; if such a Truth was in place my ability to act would be possible because thoughts are experiences and are theoretical in the same way the world of “matter” is; they are mirror images; our ability to know the said mathematical-physical reality is because of thought only; what really is there is a phenomenological interface of minds, with “matter” being of no import. The reality (“the true reality”) that i am proposing is logical in that it is truth, but also must have something to do with qualia because logical truths do not exist independently of qualia, like in a computer. So i propose a causal substance which can act as body/matter, and mind/thought, because necessarily it is monadic, like a soul/spirit essence which is connected to the Truth, or is a theoretical division (Truth is what is - dynamically and stably, not “monads” mysteriously interacting). So.. when we both know an empirical truth, say the speed of that electron, it is because we are not separate from that electron nor each other, necessarily. Everything bears out that physicalism cant reduce anything effectively.

I know this is out of style, and i know there are weaknesses, but nothing else comes close to explaining reality in such a neat, elegant package, I think.