‘Gedanken’ is a German word for ‘thought’. A
thought experiment is one you carry out in your head. In physics, the term
gedanken experiment is used to refer to an
experiment that is impractical to carry out, but useful to consider because
it can be reasoned about theoretically. (A classic gedanken experiment of
relativity theory involves thinking about a man in an elevator accelerating
through space.) Gedanken experiments are very useful in physics, but must
be used with care. It's too easy to idealize away some important aspect of
the real world in constructing the ‘apparatus’.
Among hackers, accordingly, the word has a pejorative connotation.
It is typically used of a project, especially one in artificial
intelligence research, that is written up in grand detail (typically as a
Ph.D. thesis) without ever being implemented to any great extent. Such a
project is usually perpetrated by people who aren't very good hackers or
find programming distasteful or are just in a hurry. A gedanken thesis is usually marked by an obvious
lack of intuition about what is programmable and what is not, and about
what does and does not constitute a clear specification of an algorithm.
See also AI-complete,
DWIM.
