Zero

Zero isn't nothing.
My father,
a mathematician,
insisted on that.
When he helped me with my homework
and I said it was
his eyes would steady, voice grow stern.
He'd correct me,
try his best to make me understand.
I couldn't comprehend
his reason,
didn't really care.
What difference did it make?
Twenty years later
and she is gone.
Now I know.
I'm up to my eyes
in the shadow-black heart of it.