Hey, here are those links to resources I promised on today's radio show.
Lets start with links to writings from Blessed Pope John Paul II:
Faith & Reason (Fides et Ratio)
The Splendour of Truth (Veritatis Splendor)
Next, let me recommend a very readable, down-to-earth presentation of the issue, Francis Beckwith & Gregory Koukl's Relativism: Feet Firmly Planted in Mid-Air
Now, for the more philosphically-minded out there, looking for a bit of a challenge. Let me point you to pertinent sections from St. Thomas Aquinas' Summa:
Natural Law, Summa Theologica > First Part of the Second Part > Question 94
Truth, Summa Theologica > First Part > Question 16
And then there a some helpful articles on these same points in the Catholic Encyclopedia (they break down Aquinas' thought a bit more):
If you come back tomorrow I'll put up some of those tips Dr. Vost and I shared for talking with people who embrace moral relativism.