Our senses are limited. This door/ gate here pictured is the metaphor of these limits and we have the clear notion there is an entire new world on the other side.
A couple of days ago we read something about cats and other mammals seeing in ultraviolet. How many times you saw your kitty focusing on something you cannot see? The lens of human eye blocks ultraviolet light so probably cats see a very different world.
It’s scary, some people say they are able to see errant spirits. But is it that silly? There are an infinity of sensorial stimuli difficult or impossible to us to interpret. Maybe these limitations block us to understand some paranormal stuff and the way we are linked to religion and spirituality.