Interesting question, which I believe could belong in this thread...
Lots of related questions immediately spring to mind - thinking about how one cites a vision automatically makes me wonder how to cite a hunch/feeling or when something "just stands to reason dunnit?". Or what if there is something you really want to be true but there is no evidence for? And better still, if there is something that needs to be true for your thesis but it keeps peskily being proven untrue... we need a whole system of such sources so we can conveniently cite them when looking to add weight to a totally dishonest argument we are making.
The future of demagoguery is looking veeeeery interesting indeed just now.