If there is no truth, then whatever you say can’t be true

Any evaluation of Nietzsche’s thought must inquire into his epistemology. How does one refute a philosopher who declares absurdity at the outset? When dealing with apostles of irrationality, I always ask them why they even bother to talk. I see no great value in my proving the absurdity of a position the proponents of which already grant its absurdity. The most consistent act of irrational philosophers would be simply to shut up. If they can say nothing meaningful (since there is nothing meaningful to say), why continue babbling? They insist, however, on speaking and writing. In a word, they argue for the “truth” of their position, but their arguments have no grounds for validity of invalidity since they have already abandoned the law of validity. (R. C. Sproul The Consequences of Ideas, p. 169).