Synopsis: The author's theory about our place in the Universe (echoes of this theory can be seen in his novel "Robot".) Rough summary: all entities can be divided into separate levels - from minerals, through plants, up to animals and human minds. No entity can perceive its "superentities" (minerals don't perceive plants, plants don't perceive animals, animals perceive human bodies but not minds); any effects of the superentities' actions will be mistaken for natural events (e.g. animals do not realize artificial structures are different from natural.) Therefore, there must exist "superentities" above human level which we cannot perceive, comprehend, or meaningfully communicate with; perhaps what we see as natural has been deliberately arranged by the superentities.