Is what we see every day that which really exists or is it even a collective delusion as a source of productiveness and innovation. Some sort of common belief that people connect with, without questioning or examining it – because the feeling’s just right, because you are instinctively convinced by what you do. And on a second level: due to similar culturally formative influences, a majority of people seem to perceive similar images of reality – this also crosses over into colours and shapes and could thus be named "joint perception".