That statement is self-refuting because it is objective. Subjectivism can't get off the ground because its fundamental premise is objective.
How can science isolate or control for a variable which cannot be isolated from the observer?
The nature of consciousness is elusive, almost like a dog chasing it's tail.
qed.
Epistemological monism easily resolves the "socratic paradox" and it looks like that's how Socrates himself resolves it.
"although I do not suppose that either of us knows anything really beautiful and good, I am better off than he is – for he knows nothing, and thinks that he knows. I neither know nor think that I know" - Socrates, in Platos Apology
> qed.
This is a contradiction. QED means you just proved something to be true. If there is a single truth (that there is only one truth) then there can be no deductive reasoning, science, etc.
You must have objective truth and reasoning in order to say anything other than "I feel..."
Empathy is a vastly underrated (and underdeveloped) skill.