The distinction which is often made (especially by the school of Faculty-Psychology) between sensation and idea or between sense-data and thought was once believed to be an actuality, but it is now believed to be only a convenience for intellectual analysis. A compromise view now regards our experience of the world as being a compound of the two, but a compound which is never split up into separate elements. This view represents a big step towards the mentalist position but is still only a step. And this position is that there is only a single activity, a single experience--thought. The idea is the sensation, the sensation is the idea. The sense datum which our present-day psychologists find as an element of experience is really their interpretation of experience. Hence it is nothing else than a thought. And that which it unconsciously professes to interpret is likewise a thought!
-- Notebooks Category 21: Mentalism > Chapter 1: The Sensed World > # 11
-- Perspectives > Chapter 21: Mentalism > # 34