Empiricism

"All truth claims are proved by empirical observation."
You cannot prove that statement by empirical observation; it is therefore self-refuting.

We can also easily demonstrate it to be false, because the following cannot be evaluated by empirical observation:
1. Existential truth: You cannot empirically prove you aren't "in the matrix".
2. Moral truth: You might empirically demonstrate negative consequences, but it cannot prove rape is evil.
3. Logical truth: All scientific endeavor must assume Logic from the outset.
4. Historical truth: no past event can be empirically tested; history is not repeatable.

Consider the absurdity: a consistent empiricist cannot consider any event of history to be true; it is therefore irrational.

Similar to 'strong' atheism, the only way you could actually know the statement to be true (rather than merely blindly believing it to be true) is by being omniscient - an attribute of God. Therefore in order to know this statement to be true, you'd have to be God.