Truth (with a capital T) is built into creation by the Creator Himself. It can’t be changed. It doesn’t depend on where you live or what you believe. It just is, but society has blurred these lines. According to our current culture, what is true for me may not be true for you. For example, Jesus is God, and the teachings of the Trinitarian God should reign supreme. Or marriage is between one man and one woman for life. Or life begins at conception and ends with a natural death. Society says that those things may be true for me but it may not be true for everyone.
Sure, not everyone may BELIEVE those things are true, but that doesn’t change their truthfulness. I may not believe that 2+2=4, but that doesn’t change the truthfulness of the statement. Truth is interesting because it is unchanged by our belief in it.
As Catholics, we don’t submit to moral relativism (flexible truth; truth that is relative to culture and belief). Truths cannot conflict. To refer to the previous example, either Jesus is God… or He isn’t. God is either the Creator, or He isn’t. He can’t be for me but not for someone else. So are you living by Truth or truth?