@JLNobody,
I take the problem of truth not as a problem of description, knowledge, which is always contextual and therefore incomplete, but has a problem of assuming the basic facticity of all experiences and not on the ability to knowing describing the correct master set, the right context, they fit (even hallucinations have to be true hallucinations). Not knowing the truth doesn't mean that there isn't a truth. For instance functions have specific contexts beyond which they make no sense, and even if so, that doesn't make them any less of real functions, they are true functions.
As I said several times even doubting, itself a function of knowledge seeking, requires a based ground to be a doubt...