"For an imperfect but vivid concrete analogue to this curious abstract phenomenon, think of what happens when a TV camera is pointed at a TV screen s… - Douglas Hofstadter

"For an imperfect but vivid concrete analogue to this curious abstract phenomenon, think of what happens when a TV camera is pointed at a TV screen so as to display the screen on itself (and that screen on itself, etc.)- what in GEB I called a "self-engulfing television", and in my later writings I sometimes call a "level-crossing feedback loop."

When and only when such a loop arises in a brain or in any other substrate, is a person-a unique new "I" - brought into being. Moreover, the more self-referentially rich such a loop is, the more conscious is the self to which it gives rise. Yes, shocking though this might sound, consciousness is not an on/off phenomenon, but admits of degrees, grades, shades. Or, to put it more bluntly, there are bigger souls and smaller souls."