If the wall in question is a 9" thick wall, you can bet ya life it is holding up something! having said that even a 4" wall can be load bearing in as much that it could be bearing weight of things like water tanks in the loft etc.
If it is a 4" try and take a look above it, ie lift floor boards or get into the loft.
If an ANY doubt call in a structural surveyor from the council, in fact that would be the best idea anyway, but have a look first, at least you will be able to tell him whats above it.