For instance, imagine if you showed up at the university where I teach and asked me to show you the university. After being shown one building after another, you begin to get frustrated and say, “Yes, I've seen this building and that building but where is the university?” I would have to point to the left side of my head and say, “it is only up here,” because it exists as a category and so it may change depending on whom you talk to. When no one is thinking about it, it doesn't exist at all.
