What principle is this?

Though I came and came, I've never come.
Though I went and went, I've never gone.

We committed a fault which is not a fault in spite of ourselves.
How can we return to our original form?

Fish enjoy swimming in fire,
and birds are flying in water.
One more thought,
birds are flying in fire,
and fish enjoy swimming in water.

What principle is this?

Written by
MASTER SUBUL SUNIM
Director of Anguk Zen Center
and Dongguk University's
International Seon Center
Translated by Boo Ahm
(Song Soo-kyong)