 We first examined this passage in regards to the Always Dreaming Doubt. That doubt raises the problem of the existence of external things. For all I know, my “waking” experiences are produced not by external things, but by processes similar to those producing my dreams. This sceptical hypothesis explains why the familiar involuntariness argument fails: the inference presupposes exactly what is at issue – namely, whether involuntarily received sensory ideas are produced by external things, rather than by a subconscious faculty of my mind.