@Ennui phil,
Random thoughts on this...
For some notions, I'd say, "I have faith"
For other notions, I believe they're based in fact.
Then again, I'd also say that there are many concepts where i have no faith nor facts.
If you have faith in something, by definition, such faith is, "... firm belief in something for which there is no proof". One says, "I believe!", another says, "I know" while dilbert stands in the corner with neither faith nor perceived knowledge.
... depending on our direction in this thread (read: semantics, support for ideas, opposition in theological systems, etc), there's a lot of ways to skin this cat.
<meow>