> This is an unhelpful nebulous statement, at its worst a circular definition and victim to the Münchhausen trilemma.

It is most certainly not circular. We are knowing agents first and know things spontaneously. Only on reflection do we begin to ask what knowledge is, what the limits of rational inquiry are, etc. But to be able to reflect on something, there must first be something to reflect on. Thus, we must know something before we can begin to consider epistemological questions or even have those questions in the first place. Methodic doubt always leads to incoherent conclusions because it is ultimately irrational.

> Not at all, I suggest to read Critique of Pure Reason.

I am not surprised by this recommendation given what you said. The Kantian position is extremely problematic and your appeal to it explains your reaction.

> I'll also note that epistemology was well established by Western philosophy long before Descartes.

This was never my claim. I only claimed that epistemology is not an ideal starting point. Obviously, epistemology predates Descartes. Modern philosophy onward (that is to say, beginning with Descartes, traditionally, anyway) shifts its concerns away from metaphysics to epistemology. Thus, epistemology supplants metaphysics as what one might call the primary concern of philosophical inquiry.

> This was never my claim. I only claimed that epistemology is not an ideal starting point. Obviously, epistemology predates Descartes. Modern philosophy onward (that is to say, beginning with Descartes, traditionally, anyway) shifts its concerns away from metaphysics to epistemology. Thus, epistemology supplants metaphysics as what one might call the primary concern of philosophical inquiry.

Critique of Pure Reason is exactly about metaphysics albeit as a critique. Modern philosophy at least in the transcendental aesthetic doesn't supplant metaphysics.

> I am not surprised by this recommendation given what you said. The Kantian position is extremely problematic and your appeal to it explains your reaction.

It’s trivial to criticize anything you’re not familiar with but that’s certainly not the way good philosophy is done.

Your hypothesis on knowing presumes that we have knowledge at all and that rationality leads to truth. Secondly, it’s nebulous because “to know” is, given the parsimony of the statement. Your argument only seems logical by the ambiguity of those concepts, “know” and “knowledge”.

Thirdly, these knowing agents are often victims to fallacies, delusions, and severe hallucinations—this strong naive realism has issues noted by even the early Greeks.

> Your hypothesis on knowing presumes that we have knowledge at all and that rationality leads to truth.

So your plan is to rely on some extra-rational means of developing this epistemology? That's quite a feat. Though I shudder to ask: how would you know your method leads to the truth?

> Thirdly, these knowing agents are often victims to fallacies, delusions, and severe hallucinations

How would you know? Wouldn't you need to have apprehended a truth by which you could judge something to be a hallucination?

I'll add that Critique of Pure Reason is saving metaphysics rather than destroying it.

The transcendental aesthetic, Kant's discovery, uses what we immediately experience as a subject (the subjective), to discover that which remains invariant by the properties of that immediate experience, necessarily existing in each human experience, and thus across all human experiences--this is known as the relativistic-objective, a good definition for a universal truth at least in the human experience (this movement from a subjective experience to the objective by universalization is the transcendental!). This is possible because our experience, by the nature of experience, is limited by our perception--thus being at the limit of what can be known; however this also means each subject has the same pure intuitions in order to have experience at all: causality, space, and time. The result is, one, communication is possible, but two, we can have universal knowledge of the 'world' because all experiences are derived from those four intuitions and thus will always be confined by them.

I shouldn't give you the answer, but rationality ends up being justified by the pure intuition of causality not because it's a special game but instead it happens to be universal in the inter-subjective as a pure intuition because it's a requirement for the 'subject' to exist at all.

I've taken some liberties to make this concise, but I really recommend to read at least The Prolegomena. You can also go through some of my previous comments to see others I've left on similar topics.