Sentience exists in multiple modes and in infinitely fine degrees of intensity or distinctness. In each mode there is a threshold of distinctness above which you are conscious of a content. This depends on all the other modes that are active at the same time. What is below the level of consciousness cannot be distinctly perceived but forms part of the horizon of the conscious content, which is as much as to say that that you can't enter the same content twice. Directed, conscious thought is its own special modality, and thought about thought, thought struggling to understand the process presently bringing it about is more special still. None of this could arise if there were not a place for it to arise. In physical reality there seems to be no problem about the place where an event is centred, it is a roughly delimited potion of physical space, or bodily space, or both, as when the dentist drills your tooth. At any rate we accept this ramified world space without question, accept that the regions we know and those we know about all add up to something quite definite and objective. The location of subjective experience is more problematic Is it a delimited region of something larger or is it all of subjective space? Can there be boundaries to it? The content already includes a frame, but for that frame to do its work it must operate within a larger frame. In order for awareness to have any internal relations, as say between a faint sensation and a less faint sensation, or between an idea and a feeling, it requires a stage and lighting. This is where it all gets so confusing. And the thinker striving to think about thought is nothing without the saliences he evokes and yet cannot stop short of being the site of own situation.