Humans have five senses,
but there might be others.
Humans can perceive three dimensions in space,
front/back, right/left, up/down.
Zero-dimensional world is like the world of a dot
where one cannot perceive anything.
One-dimensional world is like the world of a line
where one can only perceive one’s front/back,
and cannot notice things on one’s right/left
or up/down.
Two-dimensional world is like the world of a plane
where one can only perceive front/back, right/left,
and cannot notice things over or under the person.
If our senses are limited, there might be an outer world
that one cannot perceive.
If one could perceive it a little bit,
the feeling might be like that of a fish in a tank,
“There is something uncertain outside feeding me.”
