The World Outside Myself, Looking In

There is a box
A perplexing thing
A puzzle.
It's open:
Peering in to find
Nothing inside.
It's closed:
Listening intently
As it rattles.
Something sounds as though it should be visible,
Something invisible.
The box is turned over,
It rattles.
The insides are exposed
Upside down:
It quivers and shivers and shakes,
But not a sound.
Peering at the ground:
There is nothing.
Searching inside the box:
There is nothing still.
Closing and shaking the box:
It rattles.
Something inside that should be visible
Is invisible.
A puzzling paradox.
Staring at the box,
Biting at nail then lip,
Reaching a hand inside:
Shock and discomfort,
The thing has teeth.
The hand is gone:
Become a thing invisible
That should be visible.
Peering, inside the box:
Is nothing.
Listening to the box:
It thumps.
But that puzzle is only part
Of a much more perplexing problem
Now.