The Defective Animal (short poem)

Out of boredom, I trick my dog:
I knock on the wood of my desk
and pretend it came from the door.
“Sic Rocky!”
The dog jumps from the couch,
tail rigid in the air,
barking savagely,
raised hackles,
barred teeth,
ready to tear the invisible intruder to shreds.
There’s no doubt clogging the wheels of this perfect machine,
as they keep turning inside the placenta of causality.  
A dark thought hits me:
The dog barks at nothing thinking it’s something,
But us humans, we bark at nothing
knowing it’s nothing.
us lowly humans,
we’re only capable of
barkings of sighs
and resigned charges.