EWTN Catholic Q&A
Natural Law
Question from Curious George on 02-18-2013:

The Church often uses what is called the "natural law" to authenticate some teaching. But doesn't this "natural law" concept change over time.

For example, didn't Aquinas claim that slave ownership was permitted by the natural law but the charging of interest on loans was not?

Answer by Richard Geraghty on 04-28-2013:

Dear Curious,

You have to know history to understand what the term "slavery" or "interest" meant in ancient and medieval times. Check out Catholic web sites to get this history. Other web sites use the complications in history to repudiate the Church's teaching on natural law. If you want examples of natural law teaching that is true for all persons in all ages for all times they are that rape, murder, abortion and artificial contraception are always intrinsically evil actions.

Dr. Geraghty