“[There is] a widespread approach to ideas which Objectivism repudiates altogether: agnosticism. I mean this term in a sense which applies to the question of God, but to many other issues also, such as extra-sensory perception or the claim that the stars influence man’s destiny. In regard to all such claims, the agnostic is the type who says, “I can’t prove these claims are true, but you can’t prove they are false, so the only proper conclusion is: I don’t know; no one knows; no one can know one way or the other.”

The agnostic viewpoint poses as fair, impartial, and balanced. See how many fallacies you can find in it. Here are a few obvious ones: First, the agnostic allows the arbitrary into the realm of human cognition. He treats arbitrary claims as ideas proper to consider, discuss, evaluate—and then he regretfully says, “I don’t know,” instead of dismissing the arbitrary out of hand. Second, the onus-of-proof issue: the agnostic demands proof of a negative in a context where there is no evidence for the positive. “It’s up to you,” he says, “to prove that the fourth moon of Jupiter did not cause your sex life and that it was not a result of your previous incarnation as the Pharaoh of Egypt.” Third, the agnostic says, “Maybe these things will one day be proved.” In other words, he asserts possibilities or hypotheses with no jot of evidential basis.

The agnostic miscalculates. He thinks he is avoiding any position that will antagonize anybody. In fact, he is taking a position which is much more irrational than that of a man who takes a definite but mistaken stand on a given issue, because the agnostic treats arbitrary claims as meriting cognitive consideration and epistemological respect. He treats the arbitrary as on a par with the rational and evidentially supported. So he is the ultimate epistemological egalitarian: he equates the groundless and the proved. As such, he is an epistemological destroyer. The agnostic thinks that he is not taking any stand at all and therefore that he is safe, secure, invulnerable to attack. The fact is that his view is one of the falsest—and most cowardly—stands there can be.”
― Leonard Peikoff, Objectivism: The Philosophy of Ayn Rand