For some reason, the phrase "turtles upon turtles upon turtles" has been ringing in my head for the last couple of days. I first heard of this in my first year in my computing theory courses when we were discussing recursion and infinite recursion (and its implementation in C/C++).
I found this from Wikipedia:
William James, father of American psychology, tells of meeting an old lady who told him the Earth rested on the back of a huge turtle. "But, my dear lady", Professor James asked, as politely as possible, "what holds up the turtle?" "Ah", she said, "that's easy. He is standing on the back of another turtle." "Oh, I see", said Professor James, still being polite. "But would you be so good as to tell me what holds up the second turtle?" "It's no use, Professor", said the old lady, realizing he was trying to lead her into a logical trap. "It's turtles-turtles-turtles, all the way!"
I didn't really think much of it until I read the article from Wikipedia - it's actually quite profound that even cosmology - and theology - are somehow affected by "turtles all the way down"!
Thinking through it, it's probably ringing in my head because of "causation" - how one thing leads to another and how the former gets created by something else... ad infinitum.
It's one of the things I am thinking about at the moment:
Do companies advertise because they have sales - and therefore, "sales drives advertising"?
Or do companies have sales because they advertise - and therefore, "advertising drives sales"?
Or in the stock market:
Do investors really drive the price of a stock down or up?
Or do investors get driven by the price of a stock?
Ahh.
It's turtles all the way down.
:D

Thanks to Andreas. at Flickr.Com for the photo, Turtle Tower