We shouldn't start these arguments again, but I cant resist.
A hat rests on a head. A head is part of a human. The human sits on a chair. The chair rests on the floor. The floor is part of the building. The building has foundations. The foundations are secured to the ground. The ground is part of the earth's geology. The planet itself is the ultimate ground of orientation. What does the planet rest upon?
A turtle, of course. And that turtle sits on anther turtle, etc.
Seriously, I think the above argument is just another way of stating the third of Thomas Aquinas's 5 arguments in favor of the existence of God, summarized here:
http://web.mnstate.edu/gracyk/courses/web%20publishing/aquinasfiveways_argumentanalysis.htm
Edit: For the record, those arguments don't convince me. I could go into quantum mechanics, but don't want to start one of those endless debates again.