The researcher can most truthfully say that what he knows best of the world is its description as it appears to be. Under microscopic examination it is seen to be undergoing changes, however slight, all the time. But why does the feeling of its reality persist? Why does the feeling that the world is really present in our experience refuse to leave us? We have to say ruefully that there are really two levels of experience and therefore of truth--the common one and a higher one.
-- Notebooks Category 21: Mentalism > Chapter 1: The Sensed World > # 113