We do not have a direct acquaintance with an external, material object; we have a direct acquaintance with our own perception only, the rest being a process of unconscious inference. We do not arrive at the notion of the man as a whole until we have experienced a compound of sensations such as his height, form, colour, and feel. A percept is the discrimination and combination of sensations, to which is added the assumption of extra-mental, separate, independent existence of the thing perceived. That a man is standing two feet away from our body in the domain of objectivity is an inference which we draw unconsciously, for the only experience which we have of him are these happenings in the eye and ear--that is, happenings which are ultimately within mind. It is only at the end of this whole process that we assume the object is in an independent, outside world. From these personal impressions our mind gets to work and makes a deduction that an outer man is there. What we really see is something mental, the existence of the material man being deduced from that of the mental experience. We do not immediately see any separate, independent, external, material man.
-- Notebooks Category 21: Mentalism > Chapter 2: The World As Mental > # 4