Human thinking can skip over a great deal, leap over small
misunderstandings, can contain ifs and buts in untroubled corners of
the mind. But the machine has no corners. Despite all the attempts to
see the computer as a brain, the machine has no foreground or
background. It can be programmed to behave as if it were working with
uncertainty, but -- underneath, at the code, at the circuits -- it
cannot simultaneously do something and withhold for later something that
remains unknown. In the painstaking working out of the specification,
line by code line, the programmer confronts an awful, inevitable truth:
The ways of human and machine understanding are disjunct.
		-- Ellen Ullman, "Close to the Machine"