'Everything must have a beginning, to speak in Sanchean phrase (Sancho Panza in Cervantes' Don Quixote [1605], Book II, line xxxiii), and that beginning must be linked to something that went before. The Hindus give the world an elephant to support it, but they make the elephant stand upon a tortoise. Invention, it must be humbly admitted, does not consist in creating out of void, but out of chaos; the materials must, in the first place, be afforded: it can give form to dark, shapeless substances, but cannot bring into being the substance itself. In all matters of discovery and invention, even of those that appertain to the imagination, we are continually reminded of the story of Columbus and his egg (Christopher Columbus [1828] by Washington Irving). Invention consists in the capacity of seizing on the capabilities of a subject, and in the power of moulding and fashioning ideas suggested to it.' - Mary Shelley's introduction to Frankenstein the Modern Prometheus. (Emphasis and notes added)

'What's the most resilient parasite? An idea. A single idea from the human mind can build cities. An idea can transform the world and rewrite all the rules. Which is why I have to steal it.' - Cobb from Christopher Nolan's Inception.

In other words, what if there is no such thing as spontaneity or originality? There must be a trigger for every thought that enters our brains. A song may trigger a memory of a person or a place, but imagine if you had never heard that song. The memory would be triggered by a smell or certain weather or even a chain of other thoughts. A thought can be triggered by a What if? but the question was still posed based on natural laws and realities. It just took the inverse direction of a regular thought.

All I'm saying is the beauty of creation is not in the idea itself but the shaping, bending, forming, and ultimately the communicating of the idea.

Another point to address. What about pure inspiration? I believe in it. Sometimes thoughts come to your head without any premeditation. They just appear without warning. So if my theory is correct, then what was the trigger? Here's my other theory. The trigger of true and pure inspiration can only be explained supernaturally or, if you will, spiritually. In the words of Graham Hess in M. Night Shyamalan's Signs 'Is it possible that there are no coincidences?'

Just a theory...