The mathematician's sense of tension is intimately related to his sense of beauty, and is what makes mathematics worthwhile doing. - 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."

The nice thing about having a brain is that one can learn, that ignorance can be supplanted by knowledge, and that small bits of knowledge can gradually pile up into substantial heaps.

Some of us, perhaps all of us, believe that it is legitimate to kill enemy soldiers in a war, as if war were a special circumstance that shrinks the sizes of enemy souls.