I will explain it to you through an example and you will understand it right away. For this example I will use the detailed account of some paranormal facts that was recently sent to me by Frederick Hermite Sinclair, professor in the Department of Applied Archeology at the University of Edinburgh, Scotland. It says:
I prefer to keep my name and credentials secret, so when I talk about myself I will refer to me with the word “I”. A month and a half ago, the University where I work (whose name I prefer to remain anonymous as well) approved my project of excavation in the O’Malley Castle with a view to the end-of-course work of my forty-one students of Applied Archeology. In the company of three students chosen drawing lots (the budget of the department is not very buoyant in recent times, so I am forced to resort to this procedure too often), we moved in the van of one of them to the castle in question. It is a half-ruined medieval castle that has been abandoned for centuries. A hellish night full of thunder and lightning we arrived at the aforementioned castle where we were greeted by an elegant butler in livery, who accompanied us to our room by the light of a candelabra. As soon as we were settled in to the guest room, we gathered around the hearth fire that burned next to the four-poster bed, in order to share our first impressions. Naturally, we were amazed at the striking discrepancy between the assumed castle’s ruinous character and its obvious signs of being inhabited. We speculate with the possibility that the department had the deference to enable a wing of the castle for our accommodation. But soon we discard it when remembering its scarce disposition of funds (it is located in some rickety barracks of the campus and lacks restrooms). After half an hour of unsuccessful lucubrations, we decided to explore outside our room provided with two oil lamps to light our way. While in the light of the lamps we marveled at the neatness and luxury we found everywhere (old paintings, tapestries, armoires, finely carved oak furniture, marble staircase …), we heard a spooky scream worthy of the protagonist of the homonym painting by Edward Munch. Out of fright, my lamp fell to the ground, leaving me in complete darkness while the horrifying scream still echoed through the stone walls. Before I had time to react, my students had turned tails and ran like criminals. I pursued them uselessly threatening them with a failing grade, but by the time I reached the courtyard of the castle the van had already left at full speed leaving me in the lurch. Drenched to the bone by a thick curtain of rain, I ran back to the castle door to shelter in the comfortable room and dry myself in the heat of the fire, when suddenly a lightning bolt lit the castle and I stopped cold, stupefied by the sight of the castle ruined. I hurried inside discovering with astonishment that it rained almost as much inside as outside, all the luxury had disappeared, there was not the slightest piece of furniture and in spite of my screams no butler in livery came to receive me. Immediately my scientific mind went to work by piece trying to find a rational explanation to what happened. Refugee of the rain under a ledge, in the end I came to the conclusion that either now I was dreaming, or I was dreaming before, or sooner or later someone had been dreaming something somewhere.