Your work is technically very interesting neverthless I have some remarks.
1/ I don't always understand the claim that the Fitch Paradox threatens Anti-Realist philosophy.
If everybody accepts the Knowability Principle restricted to basic propositions,
it sounds more like a victory than a defeat for the knowability advocates.
It seems that what is threatened is more the capacity of modal logic to represent the knowability.
2/ In your intuitionistic frame, as you say in proposition 5.8, it is impossible to have 'A'
and 'not K A'
in the same world.
So the Fitch Paradox is avoided but the result is a very poor epistemic logic where you cannot express that some truths are unknown.
3/ more technically in the figure below the proposition 5.7
I don't understand what happens in the world y
You have y Rk y
; y Rk z
; y: p
; z: not p
but you have not 'y: not K p'
Does it stand that 'y: not not K p'
It is very counterintuitive.
Else I wrote a dissertation on these points.
I have published a - maybe insufi ... (read more