The BBC interviewed Guillermo del Toro, who's filming the adapation of Tolkien's "The Hobbit". And even though he was talking about his novels and his movies, this quote jumped out at me as being the very heart of why Toobworld exists......
"I believe that creatures and places can exist if they exist in the collective imagination. Although we'll never find a vampire corpse or a real alternate species of human or sub-human, they do exist by virtue of the fact that we have all willed them into reality. The same as dragons and a few other creatures."
It's a point that comes up early in my Toobworld novel!