Now that I compose music more regularly, I have a slightly different view on that. I now tend to think it comes from within, like the cummulative product of all subconsceous experiences, engrained in our brain by countless life events. These get twisted by daily external events, moods, etc and the combined outcome is the "Inspiration" we use for creativity.
In a way, we are basically creativity factories, continuously recycling and churning out new ideas from the exiting baggage of building blocks we carry through our life.
Perhaps, I am being too philosophical here. It would be interesting to hear what everyone else thinks.
Wherever it comes from, I am having tons of inspiration right now and in a great mood to compose while the creative juices are flowing!