In his letter to the Ephesians, St. Paul wrote “Slaves, be obedient to those who are your earthly masters…” (Ephesians 6:5) Slavery was widely accepted in the ancient world, and St. Paul did not make any direct challenge to the practice. In the CCC (Catechism of the Catholic Church) of the modern day, we find that in paragraph 2414, it says that the enslavement of human beings is a sin. Did the Church change her teachings on slavery? In the first place, how should we understand the concept of “change”?