In the Book of Songs we read:
“The presence of the subtle spirits
can’t be experimented nor checked;
However, we mustn’t stop searching for them.”
These subtle, imperceptible particles show themselves through the corporeal beings; since they really and truly exist, they can’t stop showing themselves in one way or another.
We can’t see these subtle spirits, since they are of a nature such that they hide from our senses. They identify themselves with the concrete things, but they are universal.