The dictionary defines inspiration as the process of being mentally stimulated to do or feel something, especially to do something creative.
I agree but, I'd also want to expand on that a bit.
I think inspiration has to come from within... or let's put it this way, something external sparks something internal and that internal spark is what triggers the flames of inspiration.
For me anyway, to be inspired to write about any particular topic or create a fictional story, it has to move me somehow. More often than not, I have to be touched personally, perhaps a memory has been evoked or something happens that elicits a feeling I've not had in a while. And that provocation always seems to come from outside myself. It can come from anywhere. From an ad on television, from watching someone's behavior in a grocery line, from having to take care of a loved one, from seeing an act of kindness... or for that matter an act of hostility or anger, from taking a walk and watching two birds flitter and fight over a speck of bread. I've even been inspired playing a video game.
Wherever it comes from, if it moves me, touches me, allows me to relate to my own past and experiences, I can more often than not feel inspired to write about it. Further, that seed can blossom into a full grown tree, a story that branches off in directions I would never imagined until I've begun writing.
Is that too limited a dimension for me as a writer? Should I push myself to write about something that may not particularly move me? I don't know but, I think if something doesn't move you then you don't feel as passionate about it. If you don't feel passionate about something, are you going to be able to produce something to move others and invite them to feel passionately as well, perhaps even inspire them? Are inspiration and passion intimately linked? Can you have one without the other?
I'm not convinced you can.