The oracle speaks

I keep trying to explain to students that 'reality' is a narrative constructed by the individual, influenced by his or her cultural context to explain events. It rarely goes in. Now I find that Terry Pratchett made the same point much more clearly in Moving Pictures:

What was it they said about gods? They wouldn't exist if there weren't people to believe in them? And that applied to everything. Reality was what went on inside people's heads.