Nobel Laureate, physicist, Bongo player, and orange juice lover Richard Feynman delivers seven incredibly cogent and accessible lectures on basic physical principles. The lectures were released as part of project Tuva thanks to Bill Gates. I especially love the last one where he describes the process of trying to discover new physical laws. Near the end he gets to this incredible phrase: "Imagination in a strait jacket". He is describing the extreme difficulty of finding an explanation that is consistent with the entire body of existing physics that is also able to resolve some of the remaining problems or unknowns. It is not just an extraordinary imagination that is necessary-- that imaginative power must find something new that still adheres to all the volumes of previously established physical fact.
To me, "imagination in a strait jacket" is a wonderfully concise description of the creative process in any field. The challenge is not just to find something new. Everyone can dream of pink elephants (even and especially when we are told not to). The struggle is to find a pink elephant that you can ride-- to find something new that is also coherent and harmonious with the existing structures in your field of work. I can dream of a million devices a day: screens you can stretch and fling like frisbees, robots that give rim jobs, self-replicating, self-assembling, self-organizing quad copters (tho that my herald the end for us). It is not hard to find something new. The struggle is to find something worth building that is also build-able; to land at the nexus of what can be done and what should be done; to dress your imagination with the strait jacket of history and still find a new way!