They have real effect. So what you think and how you think is very important. It's never a casual matter. So, the visions that humans see are just as real as any city. A world of concepts can be like scripture.
Concept precedes reality.
Concept IS reality. Not long ago, you almost died when an artery burst in your brain. It could have been the end of your days. I had always been taught to never be satisfied. That was the deal Faust made with Mephistopheles.