Euthyphro question:

If all that is pious is just, but not all that is just is pious, what is the relation between justice and piety?

Piety is a part of justice. The same relation would hold between native Texans and Americans when one says that all native Texans are Americans but not all Americans are native Texans.

Justice is a part of piety. The same relation would hold between native Texans and Americans when one says that all native Texans are Americans but not all Americans are native Texans.

Piety and justice are really one and the same, so that all just actions are pious and all pious actions are just.

Piety and justice are really opposites, because if a pious action is pious because the gods love it$,$ and the gods love unjust actions $($like Zeus swallowing his own sons$),$ then piety and injustice go hand in hand.