All our ordinary experience of the world is derived from the activity of the sense-organs. But a conviction of mentalism's truth can only be derived from rational thinking or mystical experience. Consequently, he who limits himself to the evidence of the sense-organs and does not perceive its relativity will not be able to perceive the truth of mentalism.

-- Notebooks Category 21: Mentalism > Chapter 1: The Sensed World > # 16