I came across this Observer article about where inspiration comes from via Liz Williams blog, but there's so much waffling nonsense in the article I ended up skimming most of it. I don't know why, but when people talk about 'inspiration' it seems to inspire them in turn to get a bit poetic, which isn't often a good idea.
Inspiration: it's simple. Your brain randomly associates from second to second. You are genetically programmed (via the DNA of your distant, distant ancestors) to envision the possible course of a day spent mammoth hunting: your species advantage is you can 'see' the grassy plains, and the herds waiting to be hunted. But you also have a strong imagination, perhaps too strong. There might be monsters! With big, sharp teeth! That leap out at you from the dark. Lions, tigers and bears.
What happened to your ancestors during the day's hunt is the reason human beings tell each other stories. It's where it all comes from. 'Inspiration' simply refers to the human brain's capacity to randomly associate a variety of elements from moment to moment, nothing more - part of a process of embellishment whereby a wolf sighted on a distant hill becomes a towering multi-fanged beast chased off by remarkable acts of bravery, the intention being to boost the story-tellers standing in the community.
Nothing airy fairy about it.
I had a terrific moment of inspiration a couple of months ago when I glanced at a book about serial killers on someone's bookshelf and recalled an idea concerning memory transference I'd used in Angel Stations.
Then, bam, it hit me ... forty-eight hours later I had a fully worked out plot for a story set in the present, a direct result of randomly associating something I'd used in a book with a blurb on the back of a cheap true crime paperback. One concept crossed with another concept led to another, fresh concept: two plus two makes five. That's inspiration.