@Setanta,
That's also a good distinction. These sentences have different meanings:
a) There is/isn't a god. (requires evidence for support)
b) I believe that there is/isn't a god. (no evidence required because of the verb)
In b), you're just reporting on your inner state, about which you are the sole authority. a), however, is a report about an external state, which would require substantiation in order to be credible.