The object which the senses directly establish contact with is regarded as one thing; the mental impression they have when thinking of that object is regarded as another and totally different thing. This is a very simple and apparently very obvious view of the matter. To the ordinary mind, by which I mean the metaphysically unreflective mind, the statement is unarguable and its implied division of Nature into mental and material, uncontestable. But if you analyse the way you perceive objects you will find that both the perceiver and the perceived are inseparable in the act of perception. You cannot show a duality of idea and thing but only a unity of them.
-- Notebooks Category 21: Mentalism > Chapter 2: The World As Mental > # 177
-- Perspectives > Chapter 21: Mentalism > # 38