Titus 1:14-15

Remember this is directed toward people in the church, and it is possible we can see here that a conscience can be defiled. The reference is very similar to what James says in James 3:11 where he says, "Does a spring send forth fresh water and bitter from the same opening?" What you get is a contaminated mixture. That is what this word "defiled" means. In this context, then, Paul is saying that these peoples' minds, which enabled them to think and reflect on things moral and spiritual, had become polluted and perverted. Their conscience no longer then had the ability to restrain them from making incorrect moral judgments.