He will come to see by experience, as science is coming to see by experiment, that this vast universe is real in its present form to his bodily senses only. As soon as his mind is freed from them, it takes on quite a different form, the old form having no further existence at all. He is then compelled to correct his false belief in the world's reality. If there were nothing more than the five senses, then this correction would make the universe an illusion. But the presence of mind in him makes it an idea.
-- Notebooks Category 21: Mentalism > Chapter 1 : The Sensed World > # 10
-- Perspectives > Chapter 21: Mentalism > # 27